Degradable urethane and urethane-urea systems

Abstract

The present invention provides a degradable ethyl carbamate and ethyl carbamate-urea system. The degradable polymers, including polyurethane and polyurethane-urea compositions, can be used as degradable polymers in oil, gas, and other applications in aqueous, non-aqueous, and dry hot environments. The present invention relates to degradable polyurethane and polyurethane-urea compositions that can be used as degradable polymers in petroleum, natural gas and other applications in aqueous, non-aqueous and dry-hot environments, and to processes for preparing the degradable polyurethane and polyurethane-urea compositions, and to mixtures for forming such compositions, such as, for example, mixtures for forming such compositions. Comprising, in one embodiment, degradable polyurethane and polyurethane-urea compositions made using a mixture of a prepolymer and one or more anhydrides (or heterocyclic compounds).

Description

[0001] This application is a divisional application of Chinese patent application No. 202080027034.3, entitled “Degradable ethyl carbamate and ethyl carbamate-urea system”, filed on February 7, 2020. Technical Field

[0002] The present invention generally relates to degradable polyurethane and polyurethane-urea compositions that can be used as degradable polymers in oil, gas and other applications in aqueous, non-aqueous and dry heat environments, and to methods of preparing the degradable polyurethane and polyurethane-urea compositions, and to mixtures for forming such compositions, including, in one embodiment, degradable polyurethane and polyurethane-urea compositions made using a mixture of a prepolymer and one or more anhydrides (or heterocyclic compounds). Background Art

[0003] Broadly speaking, degradable polymers are an important class of materials that provide a useful life for a certain period of time and then break down when exposed to certain fluids, temperatures and / or operating conditions. The degradation process reduces or eliminates the need for additional manufacturing or processing steps, saving time, cost, complexity and potential downtime. Degradable polymers have many applications in industrial, consumer, electronics, aerospace, mining, petrochemical, medical and other manufacturing industries. The types of polymers that are capable of degradation include both glassy and rubbery networks.

[0004] Each class of polymers and operating environment presents specific challenges in designing networks that provide the desired utility, physical, mechanical, electrical, optical, thermodynamic, chemical, temperature, environmental tolerance, and / or other functional properties that subsequently degrade at a desired rate into a physical state and / or chemical species that contributes to a useful degradation profile and product. The strategies used to design polymers and types of degradation pathways, along with the triggers, cofactors, and / or physical, chemical, mechanical, biological, or other mechanisms that lead to polymer decomposition, are a complex problem that is influenced by a variety of factors including, but not limited to, time, temperature, diffusion, reaction kinetics, solubility, interaction energy, chemical exposure, radiation, oxygen content, concentration gradients, electrochemical potential, aqueous and / or non-aqueous media, pH, and / or biological activity.

[0005] US2016 / 0290091 describes a degradable sealing member for a downhole tool, which is formed by ester, amide or urethane bonds and preferably aliphatic polyesters. However, the degradable polymer is limited to thermoplastic materials.

[0006] US2017 / 0152371 describes a degradable polyurethane containing polymer-bound carboxylic acid groups. Several issues with polymer-bound groups are limited solid-state mobility, which slows down the diffusion and reaction kinetics of polymer degradation. Another problem with acid groups in the uncured polymer is the reaction with isocyanate groups during the curing process, which can produce bubbles and lead to many defects.

[0007] Reactions between anhydrides and isocyanates and / or curing agents and active hydrogen are well known; see, for example, US3314923, US3541038, US3592789, US3708458 and US4156065. These reactions form imides, amides or amide-imides at low temperatures of 50°C. These reactions produce carbon dioxide and / or water as by-products. Carbon dioxide and water can lead to the formation of large amounts of bubbles in hot cast polyurethanes (such as high density foams) and reduce properties that limit the utility of the polymer.

[0008] US 4070310 discloses, for example, a process for producing polyurethane foams comprising a mixture of a polyisocyanate component, a component containing isocyanate-reactive hydrogens and an organic compound which decomposes to release carbon dioxide. The organic compound can be different types of anhydride derivatives which release carboxylic acid compounds when decomposed.

[0009] According to EP 1491579, carboxylic acid compounds can act as degradation agents for cured polyurethanes. EP 1491579 discloses decomposers containing anhydride groups. However, EP 1491579 does not disclose uncured polyurethane-forming compositions comprising an isocyanate component, an isocyanate-reactive component and a degradation agent.

[0010] Problems with the prior art include the use of rigid or brittle polymers that introduce hydrolyzable bonds; the use of reagents that produce side reactions that result in bubbles, voids, and loss of properties that make it difficult to mold parts; the use of polymer-binding reagents that restrict solid-state diffusion; the need for compression molding operations to produce void-free articles; and the use of active degraders to catalyze chain growth and / or crosslinking reactions when the active degraders are added in amounts required to degrade the polymer, resulting in a shortened pot life and a gel time that is too short to mold into useful articles. Based on the prior art, it was not expected that unreacted anhydrides or heterocyclic compounds could be incorporated and cured within the reactive urethane network.

[0011] Therefore, a need has been recognized to overcome the shortcomings of the prior art.

[0012] Surprisingly, it has been discovered that by forming the polymer matrix faster than the reaction rate of the anhydride with the isocyanate or curing agent, anhydrides and / or heterocyclic compounds can be incorporated into the urethane network with minimal side reactions, thereby preparing degradable polymers at temperatures previously thought impossible.

[0013] It has been found that novel degradable polyurethane and / or polyurethane-urea containing compositions can be prepared with shorter useful lives compared to conventional compositions. Useful life is broadly understood as the total life of a product in use. As can be appreciated, any particular useful life will vary greatly depending on the use of the product. Such novel degradable polyurethane and / or polyurethane-urea containing compositions exhibit increased degradation when exposed to degradation conditions such as aqueous, non-aqueous and / or thermal environments (e.g., 25° C. to about 350° C.), thereby providing greater utility, flexibility and convenience of use.

[0014] It was further discovered that by selecting new combinations of different isocyanates, diols, polyols, prepolymers, curing agents and anhydrides, the service life, degradation rate and tack level can be significantly altered.

[0015] If not otherwise stated herein, it is assumed that all patents, patent applications, patent publications, and other publications mentioned and cited herein are fully incorporated by reference as if fully set forth herein.

[0016] For a better understanding of the present invention and other and further features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings.The scope of the invention will be pointed out in the appended claims. Summary of the invention

[0017] According to at least one currently preferred embodiment of the present invention, a polyurethane forming composition is broadly contemplated, comprising: an isocyanate component, an isocyanate reactive component, a degradation agent, and optionally one or more additives. In one embodiment, the stoichiometric equivalent of the isocyanate component to the isocyanate reactive component is from about 80% to about 120%, and in another embodiment from about 85% to about 110%.

[0018] In a further embodiment, the isocyanate reactive component is a chain extender, a crosslinker, a polyol or a combination thereof. In another embodiment, the polyurethane formed by the composition reaction has increased degradability compared to the polyurethane formed by the above-mentioned similar composition without the c) degradation agent. In another embodiment, the degradation agent comprises at least one anhydride compound or a heterocyclic compound, and can be present in an amount of about 0.25wt% to about 25wt% based on the total amount of isocyanate and isocyanate reactive components. In another embodiment, the isocyanate component includes a diisocyanate or a polyisocyanate. In another embodiment, the reactive component includes one or more polyols.

[0019] In a further embodiment of the present invention, there is a polyurethane composition formed from the reaction of a polyurethane-forming composition comprising: an isocyanate component, an isocyanate-reactive component, a degradation agent, and optionally one or more additives.

[0020] In a further embodiment of the present invention, there is a polyurethane composition comprising the reaction product of: i) a modified prepolymer formed from a mixture of a prepolymer and a degradation agent, ii) a chain extender, and iii) optionally one or more additives. In one embodiment, the prepolymer is formed from the reaction of a diisocyanate and a polyol.

[0021] In a further embodiment of the invention, there is an article formed from a polyurethane forming composition, the composition comprising an isocyanate component, an isocyanate reactive component, a degradation agent, and optionally one or more additives. In a further embodiment of the invention, there is an article comprising a polyurethane composition, the composition comprising the reaction product of: i) a modified prepolymer formed from a mixture of a prepolymer and a degradation agent, ii) a chain extender, and iii) optionally one or more additives.

[0022] In a further embodiment of the present invention, there is a method for degrading a degradable polyurethane, comprising: providing a polyurethane article, subjecting the article to an aqueous, non-aqueous and / or thermal environment or a combination thereof at 25°C to about 350°C, wherein the subjecting step causes a decrease in one or more of (i) mechanical properties of the article, including hardness, tensile strength, elongation and / or sealing pressure, (ii) a soluble portion, (ii) a liquid portion, or (ii) a solid portion, wherein the solid portion can be broken into small pieces.

[0023] In one embodiment of the present invention, the article formed from the polyurethane-forming composition is substantially free of bubbles.

[0024] In another embodiment, there is a polyurethane-forming composition comprising an isocyanate component comprising toluene diisocyanate (TDI), an isocyanate-reactive component comprising poly(ethylene adipate) glycol and a 4,4'-methylenebis(o-chloroaniline) (MOCA) chain extender, a degradation agent comprising hexahydrophthalic anhydride (HHPA), and in one embodiment, TDI is reacted with the poly(ethylene adipate) glycol to form a prepolymer having low free monomer, wherein the free monomer content is from 0.01 wt% to 10.0 wt% based on the prepolymer, and from 0.05 wt% to 5.0 wt% in another embodiment, and in another embodiment, the HHPA is present in an amount from about 3 wt% to about 20 wt% based on the prepolymer.

[0025] In another embodiment, there is a polyurethane forming composition comprising: an isocyanate component comprising methylene-bis-(phenyl isocyanate) (MDI), an isocyanate reactive component chain extender comprising poly(ethylene adipate) diol and hydroquinone-bis-hydroxyethyl ether (HQEE), a degradation agent comprising maleic anhydride, and in one embodiment, the MDI is reacted with the poly(ethylene adipate) diol to form a prepolymer having a low free monomer content of 0.01 wt % to 10.0 wt % and in another embodiment, 0.05 wt % to 5.0 wt % based on the prepolymer, and in another embodiment, the HQEE is present in an amount of about 3 wt % to about 20 wt % based on the prepolymer.

[0026] For a better understanding of the present invention and other and further features and advantages thereof, reference is made to the following description in conjunction with the accompanying drawings, and the scope of the invention will be pointed out in the appended claims. As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a graph showing the results of water immersion of the polyurethane of Example 1.

[0028] Figure 2 is a graph showing the perchem impregnation results of the polyurethane of Example 1.

[0029] Figure 3 is a graph showing the heat aging results for the polyurethane of Example 1.

[0030] Figure 4 : is a graph showing the water immersion results of the polyurethane of Example 2.

[0031] Figure 5 is a graph showing the perchem impregnation results of the polyurethane of Example 2.

[0032] Figure 6 is a graph showing the heat aging results for the polyurethane of Example 2.

[0033] Figure 7 : is a graph showing the water immersion results of the polyurethane of Example 3.

[0034] Figure 8 is a graph showing the Perchem impregnation results of the polyurethane of Example 3.

[0035] Fig. 9 is a graph showing the heat aging results for the polyurethane of Example 3.

[0036] Fig.10 This is a graph showing the water immersion results of the polyurethane of Example 4.

[0037] Fig.11 : is a graph showing the water immersion results of the polyurethane of Example 10.

[0038] Fig.12 is a graph showing the perchem impregnation results of the polyurethane of Example 12.

[0039] Fig.13 is a graph showing the perchem impregnation results of the polyurethane of Example 12.

[0040] Fig.14 : is a graph showing the water immersion results of the polyurethane of Example 14.

[0041] Fig.15 is a photograph of the unimpregnated polyurethane of Example 14 (cured 89A, unimpregnated).

[0042] Fig.16 This is a photograph of the polyurethane of Example 14 immersed in water (immersed in water at 80° C. for 4 days).

[0043] Fig.17 This is a photograph of the polyurethane of Example 14 immersed in water (immersed in water at 80° C. for 11 days). DETAILED DESCRIPTION

[0044] The polyurethane composition of the present invention is formed by the chemical reaction of the components of the polyurethane forming composition, i.e., the reaction between an isocyanate component such as a diisocyanate, an isocyanate reactive component such as a polyol, a chain extender or a crosslinking compound and a combination thereof, and a degradation agent such as an anhydride or a heterocyclic compound agent, thereby forming repeated urethane groups, usually in the presence of a catalyst and / or other additives. Generally speaking, esters, ethers, ureas and aromatic rings are also present together with the urethane bonds in the formed polyurethane backbone. When (di)amines are used as chain extenders to further extend the polyurethane chains formed by the reaction between the isocyanate component and the isocyanate reactive component, polyurethane-ureas are formed. Unless otherwise expressly specified, as used throughout this application, polyurethanes should be understood to include polyurethane-ureas and poly(urea) networks.

[0045] The polyurethanes of the present invention can be formed into many useful articles by various known methods such as coating, casting, compression molding, injection molding and grinding processes. In one embodiment, such articles include those used as tools or appliances in underground applications. Exemplarily, such articles include baffles, hold down dogs and springs, screen protectors, sealed hole protectors, electric submersible pump space joints (space out subs), full-bore guns, chemical packaging, slips, dogs, spring and collet limiters, bushing retaining sleeves, timed actuators, emergency grab releases, chemical packaging containers, screen protectors, beaded screen protectors, whipstock lugs (whipstock lugs), whipstock coatings, pins, set screws, emergency release tools, gas generators, mandrels, release mechanisms, segmented rings, C-rings, perforating gun assembly systems, decomposable whipstocks for casing outlet tools, shear pins, decomposable body locking rings, mud motor stators (mud motorstators), progressive cavity pump stators (progressive cavity pump stators or shear screws; pumpable tools such as plugs, direct connect plugs, bridge plugs, scraper plugs, frac plugs, components of frac plugs, sand control bead screen plugs, inflow control device plugs, polymer plugs, implicit scraper plugs, cementing plugs, balls, steering balls, shift and positioning balls, wiper element protectors, buoyancy recorders, pumpable collets, float shoes, or darts; flow suppression tools such as seals, high pressure bead frac screen plugs, screen base pipe plugs, coatings for balls and bases, compression seal elements, expandable seal elements, O-rings, attachment seals, bullet seals, sub-surface safety valve seals, sub-surface safety valve flapper seals, dynamic seals, V-rings, support rings, drill bit seals seal, liner port plug, large air disk, large air chamber disk, debris barrier, drill bit energized liner plug, inflow control device plug, baffle, seat, ball seat, direct connect disk, drilled linear disk, gas lift valve plug, fluid loss baffle, electric submersible pump seal, shear out plug, flapper valve, gas lift valve or sleeve.

[0046] Isocyanate components of the present invention include di- or polyfunctional isocyanates containing two or more -NCO groups per molecule. Isocyanates may include aliphatic, alicyclic, polycyclic or aromatic isocyanate monomers. In addition, the isocyanate components may be monomeric, oligomeric, polymeric, prepolymer and / or block systems. Examples of diisocyanate monomers suitable for use in embodiments of the present invention include 2,4'- and 4,4'-methylene-bis-(phenyl isocyanate) (MDI), 2,4'- and 2,6'-toluene diisocyanate (TDI), p-phenylene diisocyanate (PPDI), toluene diisocyanate (TODI), naphthalene-1,5-diisocyanate (NDI), 1,6-hexane diisocyanate (HDI), dibenzyl-4,4'-diisocyanate, isophorone diisocyanate (IPDI), 1,3'- and 1,4'-xylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,3'- and 1,4'-cyclohexyl diisocyanate (CHDI), 1,1'-methylene-bis(4-isocyanatocyclohexane) (HDI), 12 Three geometric isomers of MDI and their mixtures.

[0047] The isocyanate reactive component of at least one embodiment of the present invention includes one or more compounds with active hydrogen groups. Active hydrogen groups include hydroxyl, amino and / or thiol functionalities. In one embodiment, the isocyanate reactive component includes a chain extender, a crosslinking agent and / or one or more polyols or any combination thereof to prepare a urethane network. Polyols include compounds having more than one hydroxyl, amino or thiol functional groups or combinations thereof. The formation of such polyols is well known in the art. Such polyols may include esters, ethers, amides, aliphatic, acrylic acid, polylactic acid, polyglycolic acid, metals, metalloids and other functionalities also known to those skilled in the art. In various embodiments, the polyol may include one or more of the following: polyether polyols, polyester polyols, polycarbonate polyols, polycaprolactone polyols, polyacrylate polyols, polylactic acid, polyglycolic acid and polyols containing different types of esters, ethers, amides and / or other repeating groups or fragments of the block, and mixtures or combinations thereof. In some embodiments, the polyol has a molecular weight range of 100 to 10,000, in one embodiment, 225 to 6,000, and in another embodiment, 250 to 3,000. In this context, molecular weight refers to the number average molecular weight in Daltons, as used herein, which is calculated by hydroxyl value measurement using ASTM E222-94 method.

[0048] In various embodiments, polyols may include diols, triols and / or higher average hydroxyl functionality and have a molecular weight range of, for example, 50 to 600, 55 to 300 in another embodiment, and 60 to 200 in another embodiment. In one embodiment, such polyols may include lower molecular weight polyols. The average hydroxyl functionality may be in the range of about 2 to 8, preferably about 2 to 3, more preferably about 2 to 2.5. Such diols or triols may include, for example, isomers of ethylene glycol, propylene glycol, isomers of butanediol, isomers of pentanediol, isomers of hexanediol, trimethylolpropane, pentaerythritol, poly (tetramethylene ether) glycol, poly (trimethylene ether) glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol and mixtures thereof.

[0049] In another embodiment of the present invention, the polyol used to prepare the prepolymer is a compound of polyester polyols. These polyols are prepared by conventional methods using a combination of diacids and diols known in the art, for example, succinates, adipic acid esters or other esters. Esters can also be prepared by condensation reactions of hydroxycarboxylic acids, for example, lactic acid or glycolic acid. Esters can also be prepared by acyl chlorides. Examples of polyester polyols are poly(adipate) glycol, poly(hexamethylene adipate) glycol, poly(ethylene adipate) glycol (PEAG), poly(diethylene adipate) glycol, poly(ethylene / propylene adipate) glycol, poly(trimethylolpropane / hexamethylene adipate) glycol, poly(ethylene / butylene adipate) glycol, poly(butylene adipate) glycol, poly(hexamethylene adipate / neopentyl glycol) glycol, poly(butylene / hexamethylene adipate) glycol (PBHAG), poly(neopentyl adipate) glycol, and mixtures, copolymers (including block and random copolymers) and terpolymers thereof.

[0050] In one embodiment, an aromatic diisocyanate is employed as the isocyanate component and a PEAG polyol is used.

[0051] The degradation agents of the present invention undergo reactions with the polyurethane matrix when exposed to aqueous, non-aqueous and / or thermal environments, which can degrade and / or destroy the polyurethane network, resulting in a loss of material properties.

[0052] Degradation agents include compounds that are relatively stable in the presence of polyurethane raw materials and processing conditions used to produce the polyurethane network. For example, in one embodiment, the degradation agent can be neutral or weakly acidic or basic during the production of the polyurethane article, and then form more strongly acidic or basic conditions during the use of the polyurethane article to more effectively degrade the article.

[0053] In one embodiment of the invention, the degradation agent is dispersed as a mixture or covalently bound to the polymer. The degradation agent, such as anhydride or heterocyclic functional compound, can be added or incorporated into a polymer matrix as a discrete compound to degrade the polymer. When the polyurethane is exposed to an aqueous environment, water will diffuse into the polymer, which will react with the degradation agent to produce active chemical species, such as acid or alkali, which will degrade or catalyze the degradation of the polyurethane network, for example, hydrolyzing anhydride to generate diacids, which will catalyze degradation pathways. In a further embodiment of the present invention, the degradation agent interacts chemically with urethane, for example, reacting with secondary nitrogen groups in the urethane backbone to destroy the polyurethane network, for example, by destroying the hard phase, reducing hydrogen bonds and / or producing acid to cause performance loss. The degradation agent of at least one embodiment of the present invention includes, for example, a compound that produces free radicals when exposed to heat, which degrades the urethane network or causes main chain rupture (for example, peroxides and azo compounds, which can produce free radicals and nitrogen).

[0054] In one embodiment, the degradation agent does not decompose to release carbon dioxide. In such embodiments, the anhydride is not used as a blowing agent to generate carbon dioxide and subsequently generate foam.

[0055] In one embodiment, the anhydride and / or heterocyclic group of the present invention includes hexahydrophthalic anhydride (HHPA), maleic anhydride, pyromellitic anhydride, 1,8-naphthalene dicarboxylic anhydride, (2-dodecene-1-yl) succinic anhydride, acetic anhydride, succinic anhydride, phthalic anhydride, propionic anhydride, methacrylic anhydride, glutaric anhydride, citraconic anhydride, butyric anhydride, isobutyric anhydride, 3,4,5,6-tetrahydrophthalic anhydride, isophthalic anhydride, diglycolic anhydride, itaconic anhydride, crotonic anhydride, trans-1,2-cyclohexane dicarboxylic anhydride, 2,3-dimethyl maleic anhydride, 2-carboxyphenylacetic anhydride, hexahydro-4-methylphthalic anhydride, 3,3-tetramethylene glutaric anhydride, valeric anhydride, internal -Bicyclo[2.2.2]oct-5-ene-2,3-carboxylic anhydride, hexanoic anhydride, stearic anhydride, cis-aconitic anhydride, trimellitic anhydride chloride, phenylsuccinic anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, palmitic anhydride, 3,4-pyridinedicarboxylic anhydride, oleic anhydride, bromomaleic anhydride, 4-methylphthalic anhydride, S-acetylmercaptosuccinic anhydride, dodecanoic anhydride, 2-octen-1-ylsuccinic acid, biphenyl anhydride, decanoic anhydride, myristic anhydride, N-methylisatoic anhydride, 2,2-dimethylsuccinic anhydride, 3-methylglutaric anhydride, phenylmaleic anhydride, 4-amino-1,8-naphthalene dicarboxylic anhydride, 4,4-(4,4'-isopropylidene) diphenyloxy)bis(phthalic anhydride), tetrachlorophthalic anhydride, tetrabromophthalic anhydride, 3-hydroxyphthalic anhydride, tetrafluorophthalic anhydride, 4-bromo-1,8-naphthalene dicarboxylic anhydride, dodecenylsuccinic anhydride, 4,4'-(hexafluoroisopropylidene)phthalic anhydride, 3-nitrophthalic anhydride, 4,4'-oxydiphthalic anhydride, 2,3-dichloromaleic anhydride, 2,3-pyrazine dicarboxylic anhydride, 4-nitrophthalic anhydride, polymer-bound isotactic anhydride, 3,6-dichlorophthalic anhydride, trifluoroacetic anhydride, benzoic anhydride, boric anhydride, 1,2,3,6-tetrahydrophthalic anhydride, trimethylacetic anhydride, methanesulfonic anhydride, 1,2, 4-Benzene trimellitic anhydride, isobutyric anhydride, methyltetrahydrophthalic anhydride, glycine anhydride, cis-5-norbornene-endo-2,3-dicarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, dodecenylsuccinic anhydride, glutaric anhydride, butylsuccinic anhydride, 1,2-cyclopentanedicarboxylic anhydride, phenoxyacetic anhydride, polypropylene-graft-maleic anhydride, polyethylene-graft-maleic anhydride, polystyrene-block-poly(ethylene-random-butylene)-block-polystyrene-graft-maleic anhydride, poly(methyl vinyl ether-alternating-maleic anhydride), polyisoprene-graft-maleic anhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, methylnadic anhydride, etc. and mixtures thereof.

[0056] The specific amount of degradation agent required varies depending on the degree of degradation required and the properties of the anhydride or heterocyclic compound used. However, the amount should be sufficient to increase the degradation of the polyurethane compared to a similar polyurethane formed without the use of a degradation agent. Degradation can be relatively quantified as a reduction in one or more of the following properties of the polyurethane composition: (i) mechanical properties (e.g., hardness, tensile strength, elongation, sealing pressure), (ii) soluble fraction, (ii) liquid fraction, or (ii) solid fraction, wherein the solid fraction can be broken into small pieces. In another embodiment, the degradation agent is present in an amount of about 0.20 wt % to about 30 wt %, in another embodiment about 5 wt % to 25 wt %, and in another embodiment about 5 wt % to 20 wt %, based on the total amount of isocyanate+isocyanate reactive components. In aqueous and non-aqueous environments, the addition of salts can accelerate the degradation rate.

[0057] In at least one embodiment, the preparation of polyurethane and polyurethane-urea involves the preparation of prepolymers. For example, isocyanate reacts with long-chain (high molecular weight) polyols to form prepolymers containing free isocyanate groups. The prepolymer can then be chain-extended with short-chain (low molecular weight) polyols or diamines to form polyurethane or polyurethane-urea. In the present invention, there is no particular restriction on the use of prepolymers or prepolymer mixtures, nor on the polyols or diisocyanate monomers that can be used to prepare prepolymers. In a broad sense, polyurethanes are generally two-phase polymers comprising alternating rigid and flexible blocks or so-called hard segments and soft segments. The soft segments are obtained from prepolymers, wherein the polyol portion mainly contributes to the elasticity of the product. On the other hand, the hard segments are composed of isocyanates and chain extenders (usually aromatic diamines or aliphatic diols). They particularly affect modulus, hardness and tear strength, and determine the upper limit use temperature by their ability to maintain association at high temperatures.

[0058] The degradable polyurethane according to one embodiment of the present invention can be obtained by mixing a polyurethane prepolymer and a degradation agent to form a "modified prepolymer" and curing the modified polymer with a chain extender, such as in one embodiment, where an anhydride or a heterocyclic compound is used as a degradation agent. It should be understood by those skilled in the art that the polyurethane composition according to the present invention can also be prepared by a method in which all ingredients are mixed simultaneously, for example, using a three-component metering mixer or a manual batching method.

[0059] The polyurethanes and prepolymers of the present invention are prepared using standard reaction methods and conditions known in the art for producing prepolymers and polyurethanes. Exemplary methods are described in, for example, US4832098, US4934425, US4921029, US4784201 and US5605657 and US2003 / 065124, the contents of which are incorporated herein by reference.

[0060] In one embodiment, the polyurethane according to the present invention can be prepared by a multi-step or one-time casting method. Subsequently, a degradation agent is added to the prepolymer, and the resulting modified prepolymer is then cured with a chain extender. A casting process can be used, wherein the curing between the prepolymer and the chain extender is performed in a mold. After curing, the polyurethane is demoulded and then post-cured by additional heat and time to fully realize the physical properties of the polyurethane network structure.

[0061] The prepolymer of one embodiment of the present invention is usually prepared using an excess of diisocyanate monomers, thereby producing a prepolymer mixture containing unreacted monomers or "free" diisocyanates. The amount of free diisocyanates can be reduced to form a low free monomer prepolymer. This low free monomer prepolymer and its preparation method are also known in the art, for example, by distillation. Any distillation equipment that can effectively operate under high vacuum, moderate temperature and short residence time can be used for this step (see, for example, US2003 / 065124). In one embodiment of the present invention, the low free monomer prepolymer used has 0.01wt% to 10.0wt%, for example, 0.05wt% to 5.0wt%, and in one embodiment, less than 0.1wt% of the free diisocyanate component, which does not react with polyols.

[0062] Generally speaking, the prepolymer obtained by the process of the present invention can have low viscosity, low monomeric diisocyanate level and high NCO content, for example, for structures above ABA, having a theoretical NCO content of about 60%, preferably above about 80% or more.

[0063] As used herein, an isocyanate reactive compound is a compound that connects multiple isocyanate chains in the formation of a polyurethane or polyurethane-urea. The isocyanate reactive compound can include a chain extender, a crosslinker and / or a polyol or a combination thereof. In a broad sense, a chain extender is a substance having two isocyanate reactive groups per molecule. A crosslinker is a compound having more than two isocyanate reactive groups per molecule. Polyols have one or more repeating segments and two or more isocyanate reactive groups per molecule. Isocyanate reactive groups include, but are not limited to, active hydrogen groups, such as hydroxyl, amino or thiol groups.

[0064] For example, the chain extender can be water, an aliphatic diol, an aromatic diamine, or a mixture thereof.The chain extender can be the same as or different from the isocyanate reactive component of the present invention.

[0065] Representative chain extenders include aliphatic diols such as 1,4-butanediol (BDO), resorcinol bis(β-hydroxyethyl) ether (HER), resorcinol bis(β-hydroxypropyl) ether (HPR), hydroquinone-bis-hydroxyethyl ether (HQEE), 1,3-propylene glycol, ethylene glycol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol (CHDM); aliphatic triols and tetraols such as trimethylolpropane; and adducts of propylene oxide and / or ethylene oxide having a molecular weight ranging from about 190 to about 500.

[0066] Many diamines are well known chain extenders for use in polyurethane compositions. Preferred diamine chain extenders include 4,4'-methylenebis(o-chloroaniline) (MOCA), 4,4'-methylenebis(2-chloroaniline) (MBCA); 4,4'-methylenebis(3-chloro-2,6-diethylaniline (MCDEA); diethyltoluenediamine (DETDA); tert-butyltoluenediamine (TBTDA); dimethylthiotoluenediamine; trimethylene glycol diparaaminobenzoate; methylenedianiline (MDA); and methylenedianiline-sodium chloride complex.

[0067] In one embodiment, the chain extender is an amine curing agent, and in this case the amine curing agent is 4,4'-methylenebis(o-chloroaniline) (MOCA).

[0068] For curing the (chain-extended) prepolymers of the present invention with amine curing agents, the -NH 2 The number of groups should be approximately equal to the number of -NCO groups in the prepolymer. In one embodiment, about 80% to about 120% is used, while in another embodiment, about 85% to about 105% of the stoichiometric equivalent is used. However, it is also known that higher stoichiometric amounts can be used. The reactivity of isocyanate groups with amino groups varies depending on the structure to which the groups are attached. It is well known, as for example, in US Pat. No. 2,620,516, that some amines react very quickly with some isocyanates, while others react more slowly. In the latter case, a catalyst may be selected to result in an increase in the reaction rate. For some aromatic diamines, it is only necessary to control the reaction temperature or the temperature of the polyurethane reactants to obtain a suitable reaction time; therefore, for diamines that are generally too reactive, a catalyst is obviously not required and a reduction in the reaction temperature is sufficient. There are a large number of commercially available catalysts that can be used to accelerate the reaction of isocyanate groups with compounds containing active hydrogen atoms. A person skilled in the art is fully capable of selecting and selecting a catalyst that suits her particular needs or wishes and adjusting the dosage to further improve her conditions. Adipic acid and triethylenediamine are typical suitable catalysts.

[0069] The curing temperature for chain extending the modified prepolymer can vary, but is generally greater than 20° C., for example, greater than 50° C. or greater than 70° C. In one embodiment, the polyurethane can be prepared by chain extending the chain of a modified prepolymer formed from a prepolymer having a low monomeric diisocyanate content with a chain extender as described above by methods known in the art.

[0070] The anhydrides can be incorporated into the urethane and / or urea polymer matrix with minimal interaction or reaction with the isocyanate and / or curing agent at concentrations, times and temperatures suitable for preparing degradable polymers, making articles and exposing the network to conditions of degradation properties. Without wishing to be bound by any particular theory, it is understood that the cured polymer contains unreacted anhydride and / or heterocyclic groups which, when exposed to aqueous, non-aqueous and thermal environments, hydrolyze upon exposure to moisture or other reactions with the polymer matrix to produce acids, bases or other chemical interactions that degrade and / or destroy the polymer network.

[0071] In embodiments of the present invention, the reaction rate between the isocyanate and the curing agent (kNCO-CUR) is greater than the kinetics of any side reactions between the isocyanate group and the anhydride or heterocyclic degradation agent compound (kNCO-ANH); and the kinetics of any side reactions between the chain extender and the anhydride or heterocyclic compound (kCUR-ANH). This favors the formation of the urethane network during the curing process with minimal reaction between the isocyanate, chain extender, and anhydride or heterocyclic compound.

[0072] The polymers described in this invention have unreacted anhydride or heterocyclic compound dispersed in the matrix at a desired concentration that reacts when exposed to aqueous, non-aqueous and / or thermal environments, resulting in degradation mechanisms and loss of performance after a desired service life. The reaction rate of the isocyanate and curing agent is faster than the rate of any side reaction between the urethane reagent and the anhydride. Side reactions between the urethane reagent and the anhydride can affect stoichiometry, network structure and morphology; produce undesirable byproducts that lead to bubbles in the part; and reduce polymer performance.

[0073] It may be desirable to change the chemical nature, chemical interactions, and reaction rates of the isocyanate, chain extender, and / or degradation agent to adjust the performance of the urethane network for a particular application. For example, the introduction of free unreacted anhydrides in the polymer can make solid chemical species more easily diffuse and migrate, thereby achieving degradation pathways. In one embodiment, the polyurethane is formed in a process in which the anhydride is solid at room temperature and liquid (molten) at the desired degradation temperature to improve diffusion within the polymer matrix. Technicians can consider the effects of the anhydride chemical structure on solubility, steric effects, and reaction kinetics. In one embodiment, anhydrides with low water solubility are introduced into the polymer matrix to effectively degrade the network. The effectiveness of anhydrides that exhibit low water solubility is surprising because it is believed that anhydrides need to exhibit high water solubility to produce free acids sufficient to degrade the urethane network.

[0074] In one embodiment, there is a two-step reaction in which the degradation agent is mixed into the urethane network while bubbles are generated in the cast article. In an aqueous environment, water diffuses into the cured polyurethane network containing the unreacted anhydride degradation agent. The anhydride hydrolyzes to produce acid, which catalyzes the hydrolysis of the ester groups, resulting in polymer backbone scission, degradation, and the generation of soluble fragments. The two-step reaction in an aqueous environment allows the preparation of essentially void-free articles and components that degrade after the desired service life. This facilitates the use of common hot casting mold opening techniques.

[0075] Although the preferred embodiments of the present invention are described herein, it should be understood that the present invention is not limited to this precise embodiment, and various other changes and modifications may be made thereto by those skilled in the art without departing from the scope or spirit of the present invention. The following examples illustrate the practice of the present invention, but are not intended to be used as limitations on the scope of the present invention.

[0076] Example:

[0077] The following compositions were prepared.

[0078] Example 1

[0079] The degradable polyurethane composition is prepared from a TDI-terminated polyester prepolymer, 14 wt% HHPA and MOCA. A low free TDI-terminated polyester prepolymer (214.57 g) having an NCO content of 5.47 wt% based on poly(ethylene adipate) glycol is heated to 56°C and mixed with 1,2-cyclohexanedicarboxylic anhydride (35.81 g). The mixture is degassed under vacuum (less than 10 mm Hg) for about 5 minutes. When the anhydride is added, the color of the prepolymer is almost unchanged. 4,4'-methylenebis(2-chloroaniline) is melted at about 125°C and degassed under vacuum (less than 10 mm Hg) for 5 minutes. 4,4'-methylenebis(2-chloroaniline) (35.69 g) is added to the prepolymer and mixed until uniform. The molar ratio of curing agent to isocyanate is 95% of the theoretical stoichiometric amount. The mixture is poured into a hot mold in a 100°C oven. The polyurethane was cured for 1 hour and then post-cured at 100°C for an additional 16 hours. The cured polymer had no bubbles and had a Shore hardness of 90A. The rectangular specimen was immersed in water at 80°C. Cracks appeared within one day and the specimen began to break into pieces after three days. The immersion and heat aging data are shown below. Within 15 days, nearly 45wt% of the urethane polymer dissolved into the water phase. The remaining polymer broke into small pieces. In a non-aqueous fluid (Perchem 1150) at 120°C, the hardness of the specimen dropped 100% in three days. The hardness of the specimen heat aged at 120°C dropped 100% in three days.

[0080] Table 1

[0081]

[0082] Example 2

[0083] The degradable polyurethane composition is prepared from a TDI-terminated polyester prepolymer, 12 wt% HHPA and MOCA. A low free TDI-terminated polyester prepolymer (214.58 g) having an NCO content of 5.47 wt% based on poly(ethylene adipate) glycol was heated to 55°C and mixed with 1,2-cyclohexanedicarboxylic anhydride (30.68 g). The mixture was degassed under vacuum (less than 10 mm Hg) for about 5 minutes. The color of the prepolymer changed little when the anhydride was added. The absence of a color change indirectly indicates that there was little interaction between the isocyanate and the anhydride. 4,4'-methylenebis(2-chloroaniline) was melted at about 125°C and degassed under vacuum (less than 10 mm Hg) for 5 minutes. 4,4'-methylenebis(2-chloroaniline) (35.75 g) was added to the prepolymer and mixed until uniform. The molar ratio of curing agent to isocyanate was 95% of the theoretical stoichiometric amount. The mixture was poured into a hot mold in a 100°C oven. The polyurethane was cured for 1 hour and then post-cured at 100°C for another 16 hours. The cured polymer was bubble-free and had a Shore hardness of 91 to 93A. The rectangular specimen was immersed in 80°C water. Cracks appeared within one day and the sample began to break into pieces after five days in water. The immersion and heat aging data are shown below. Within 15 days, nearly 45wt% of the urethane polymer was dissolved into the water phase. The remaining polymer broke into small pieces. In a non-aqueous fluid (Perchem 1150) at 120°C, the hardness of the specimen dropped 100% in 6 days. The hardness of the sample heat aged at 120°C dropped 100% in three days.

[0084] Table 2:

[0085]

[0086] Example 3

[0087] The degradable polyurethane composition is prepared from a TDI-terminated polyester prepolymer, 16 wt% HHPA and MOCA. A low free TDI-terminated polyester prepolymer (214.6 g) having an NCO content of 5.47 wt% based on poly(ethylene adipate) glycol is heated to 60°C and mixed with 1,2-cyclohexanedicarboxylic anhydride (40.92 g). The mixture is degassed under vacuum (less than 10 mm Hg) for about 5 minutes. When the anhydride is added, the color of the prepolymer is almost unchanged. 4,4'-methylenebis(2-chloroaniline) is melted at about 125°C and degassed under vacuum (less than 10 mm Hg) for 5 minutes. 4,4'-methylenebis(2-chloroaniline) (35.65 g) is added to the prepolymer and mixed until uniform. The molar ratio of curing agent to isocyanate is 95% of the theoretical stoichiometric amount. The mixture is poured into a hot mold in a 100°C oven. The polyurethane was cured for 1 hour and then post-cured at 100°C for another 16 hours. The cured polymer contained some bubbles and had a Shore hardness of 88A. The rectangular specimen was immersed in water at 80°C. Cracks appeared within one day and the specimen began to break into pieces after five days in the water. The immersion and heat aging data are shown below. Within 15 days, nearly 45wt% of the urethane polymer dissolved into the water phase. The remaining polymer broke into small pieces. In a non-aqueous fluid (Perchem 1150) at 120°C, the hardness of the specimen dropped 100% in 3 days. The hardness of the sample heat aged at 120°C dropped 100% in one day.

[0088] Table 3:

[0089]

[0090] Example #4

[0091] Polyurethane compositions of 88 to 89A were prepared from TDI-terminated polyester prepolymers cured with MOCA using three different stoichiometric ratios (90%, 100%, and 110%, respectively) to serve as a baseline for polymer degradation rates without the addition of any anhydride. Low free TDI-terminated polyester prepolymers (222.80, 220.12, and 217.54 g) with an NCO content of 4.27 wt% based on poly(ethylene adipate) glycol were heated to about 90°C and degassed under vacuum (less than 10 mm Hg) for 5 minutes. 4,4'-methylenebis(2-chloroaniline) was melted at about 125°C and degassed under vacuum (less than 10 mm Hg) for 5 minutes. 4,4'-methylenebis(2-chloroaniline) (27.43, 29.65, and 32.47 g, respectively) was added to the prepolymer and mixed until homogeneous. The mixture was poured into a hot mold in an oven at 105°C. The polyurethane was cured for 1 hour and then post-cured at 105°C for an additional 16 hours. The cured polymer had no bubbles and had a Shore hardness of 88 to 89A. The rectangular specimens were immersed in water at 80°C. One set of specimens showed cracking after 21 days. After 14 days, the weight loss was less than 2%. The water immersion data is shown below. The addition of anhydride significantly accelerated the degradation.

[0092] Example 5

[0093] The degradable polyurethane composition is prepared from a TDI-terminated polyester prepolymer, 20 wt% HHPA and MOCA. A low free TDI-terminated polyester prepolymer (214.62 g) having an NCO content of 5.47 wt% based on poly(ethylene adipate) glycol is heated to 90°C and mixed with liquid 1,2-cyclohexanedicarboxylic anhydride (50.0 g). The mixture is degassed under vacuum (7 mm Hg) for about 10 minutes. The mixture is clear and bubble-free. The color of the prepolymer does not change when the anhydride is added. 4,4'-methylenebis(2-chloroaniline) is melted at about 125°C and degassed under vacuum (less than 10 mm Hg) for 5 minutes. 4,4'-methylenebis(2-chloroaniline) (35.31 g) is added to the prepolymer and mixed until uniform. Based on the theoretical stoichiometric amount, the molar ratio of curing agent to isocyanate is 95%. The mixture is poured into a hot mold in a 100°C oven. The polyurethane was cured for 1 hour and then post-cured at 100°C for an additional 16 hours. The cured polymer was an opaque white color, should be translucent beige, and contained many bubbles (like a high density foam). The cured polymer had a Shore hardness of 74A. The hardness of the polymer is expected to be 90 to 95A. The specimens were not impregnated.

[0094] Example 6

[0095] A degradable polyurethane composition was prepared from a TDI-terminated polyester prepolymer, 20 wt% HHPA, and E300. A low free TDI-terminated polyester prepolymer (220.78 g) having an NCO content of 5.47 wt% based on poly(ethylene adipate) glycol was heated to 61°C and mixed with 1,2-cyclohexanedicarboxylic anhydride (50.0 g) heated to 49°C to melt the anhydride. The mixture was degassed under vacuum (8 mm Hg) for about 4 minutes. The mixture was clear and bubble-free. The color of the prepolymer did not change when the anhydride was added. This indirectly indicates that there was little interaction between the anhydride and the isocyanate at these processing temperatures. Dimethylthiotoluenediamine (29.21 g) was added to the prepolymer at 25°C and mixed until uniform. Based on the theoretical stoichiometric amount, the molar ratio of curing agent to isocyanate was 95%. The color of the prepolymer and anhydride mixture did not change after the addition of the aromatic curing agent. This indirectly indicates that there is little molecular interaction between the anhydride and the curing agent at this processing temperature. The mixture was poured into a hot mold in a 100°C oven. After five minutes at 100°C, small microbubbles appeared in the gelled polymer. The polyurethane was cured for 1 hour and then post-cured at 100°C for another 16 hours. The cured polymer was translucent (amber) and contained bubbles. The Shore hardness of the cured polymer was 83A, which was expected to be 90 to 95A. The samples were not impregnated.

[0096] Example 7

[0097] The degradable polyurethane composition was prepared by using a three-step curing scheme to eliminate bubbles generated by the side reaction with anhydride from a TDI-terminated polyester prepolymer, 20 wt% HHPA and E300. A low free TDI-terminated polyester prepolymer (220.78 g) with an NCO content of 5.47 wt% based on poly (ethylene adipate) glycol was heated to 52 ° C and mixed with 1,2-cyclohexanedicarboxylic anhydride heated to 42 ° C to melt the anhydride. The mixture was degassed under vacuum (3-5 mm Hg) for about 10 minutes. The mixture was clear and bubble-free. When the anhydride was added, the color of the prepolymer did not change. This indirectly indicates that there is almost no interaction between the anhydride and the isocyanate at these processing temperatures. Dimethylthiotoluenediamine (29.21 g) was added to the prepolymer at 25 ° C and mixed until uniform. Based on the theoretical stoichiometric amount, the molar ratio of curing agent to isocyanate is 95%. There was no color change in the prepolymer and anhydride mixture after the addition of the aromatic curing agent. This indirectly indicates that there is little molecular interaction between the anhydride and curing agent at this processing temperature. The mixture was poured into a mold at 25°C and cured for 1 hour. The mold was placed in an oven at 60°C for 1 hour. No bubbles or color change were observed. The mold was placed in an oven at 100°C for 15 hours. The cured polymer was a translucent amber color with no bubbles. The hardness of the cured polymer was 95A, which is the expected value.

[0098] Example 8

[0099] A degradable polyurethane composition was prepared from a TDI-terminated polyester prepolymer, 20 wt% maleic anhydride and E300 to examine the effect of anhydride on increased water solubility and reduced steric effect. A low free TDI-terminated polyester prepolymer (220.71 g) having an NCO content of 5.47 wt% based on poly(ethylene adipate) glycol was heated to 47°C and mixed with maleic anhydride (50.00 g) heated to 75°C to melt the anhydride. The color of the prepolymer changed from light amber to transparent yellow, which indirectly indicated that there was an interaction between the anhydride and the isocyanate. The mixture was degassed under vacuum (11 to 5 mm Hg) for about 10 minutes. The prepolymer mixture was a transparent, bubble-free yellow. Dimethylthiotoluenediamine (29.21 g) was added to the prepolymer at 25°C and mixed until uniform. Based on the theoretical stoichiometric amount, the molar ratio of curing agent to isocyanate was 95%. When the aromatic amine was added, the prepolymer mixture immediately changed color to a transparent dark red, which indirectly indicated that there was a strong molecular interaction between the anhydride and the aromatic curing agent at this processing temperature. The mixture was poured into a 100°C mold. The polymer gelled after 10 minutes at 100°C, but no bubbles were present. Microbubbles appeared after 15 minutes. The polyurethane was cured at 100°C for 1 hour and post-cured at 100°C for 16 hours. The cured polymer was a transparent dark reddish brown color, containing many bubbles throughout the network. The diameter of the bubbles was several millimeters. The hardness of the cured polyurethane was 70A. The hardness is expected to be 90 to 95A. Maleic anhydride has a strong interaction with TDI and dimethylthiotoluenediamine.

[0100] Example 9

[0101] A low free TDI end-capped succinate prepolymer was prepared from TDI, polyethylene succinate and diethylene glycol to increase degradation kinetics. TDI-65 (1525 g), phosphoric acid (0.0449 g), polyethylene succinate glycol (2817 g) and diethylene glycol (163 g) were charged into a reactor to synthesize a crude prepolymer. The crude prepolymer was stripped in a thin film evaporator at elevated temperature and vacuum. The stripped prepolymer had an NCO value of 5.38 wt%.

[0102] Example 10

[0103] The degradable polyurethane composition was prepared from the TDI-terminated polyester prepolymer prepared in Example 9, 12 wt% HHPA and MOCA. A low free TDI-terminated polyester prepolymer (150.57 g) having an NCO content of 5.38 wt% based on poly(ethylene succinate) glycol was heated to 68°C and mixed with 1,2-cyclohexanedicarboxylic anhydride (21.14 g). The mixture was degassed under vacuum (less than 10 mm Hg) for about 10 minutes. The color of the prepolymer changed little when the anhydride was added. The absence of a color change indirectly indicated that there was little interaction between the isocyanate and the anhydride. 4,4'-methylenebis(2-chloroaniline) was melted at about 125°C and degassed under vacuum (less than 10 mm Hg) for 5 minutes. 4,4'-methylenebis(2-chloroaniline) (24.46 g) was added to the prepolymer and mixed until uniform. The molar ratio of curing agent to isocyanate was 95% of the theoretical stoichiometric amount. The mixture was poured into a hot mold in a 100°C oven. The polyurethane was cured for 1 hour and then post-cured at 100°C for an additional 16 hours. The cured polymer was bubble-free and had a Shore hardness of 97A. The rectangular specimen was immersed in water at 80°C. Cracks appeared within one day and the sample began to break into pieces after six days. The water immersion data is shown below. Within 7 days, nearly 35 wt% of the urethane polymer was dissolved into the water phase. The remaining polymer was easily broken into small pieces.

[0104] Embodiment 11

[0105] The degradable polyurethane composition is prepared from an MDI-terminated polyester prepolymer, 10 wt% maleic anhydride and 1,4-butanediol. An MDI-terminated polyester prepolymer (227.82 g) having an NCO content of 9.57 wt% based on polyethylene adipate diol is heated to 70°C and mixed with molten maleic anhydride (25.5 g). 230.76 g of the prepolymer / anhydride mixture is transferred to a second container and degassed under vacuum (>2 mm Hg) for about 25 minutes. 1,4-butanediol (20.46 g) is added to the prepolymer at 25°C and mixed until uniform. The molar ratio of curing agent to isocyanate is 95%. The mixture is poured into a 100°C mold. The polyurethane is cured at 100°C for 1 hour and then post-cured at 100°C for 16 hours. The hardness of the cured polyurethane is 90A. There are no bubbles in the molded parts.

[0106] Example 12

[0107] The degradable polyurethane composition was prepared using an MDI-terminated polyester prepolymer (187.28 g) having an NCO content of 6.71 wt% based on polyethylene adipate glycol, 10 wt% maleic anhydride (25.15 g) and 1,4-butanediol (12.93 g) with and without 10 wt% sodium chloride (25.34 g). The hardness of the sample using sodium chloride immersed in Perchem 1150 (non-aqueous lysate) at 120°C decreased by 100% in one day, while the hardness of the sample without sodium chloride decreased by only about 50% in three days.

[0108] Example 13

[0109] The degradable polyurethane composition was prepared from an MDI-terminated polyester prepolymer, 20 wt% pyromellitic anhydride and 1,4-butanediol. An MDI-terminated polyester prepolymer (227.82 g) having an NCO content of 9.57 wt% based on polyethylene adipate diol was heated to 85°C and mixed with pyromellitic anhydride powder (50.95 g). 258.2 g of the prepolymer / anhydride mixture was transferred to a second container and degassed under vacuum (>2 mm Hg) for about 15 minutes. 1,4-butanediol (20.6 g) was added to the prepolymer at 25°C and mixed until uniform. The molar ratio of curing agent to isocyanate was 95%. The mixture was poured into a 100°C mold. The polyurethane was cured at 100°C for 1 hour and then post-cured at 100°C for 16 hours. The hardness of the cured polyurethane was 95A. No bubbles were observed in the molded parts.

[0110] Embodiment 14

[0111] The degradable polyurethane composition is prepared from MDI-terminated polyester prepolymer, 10wt% maleic anhydride and HHPA. A low free MDI-terminated polyester prepolymer (185.41 g) having an NCO content of 3.41wt% based on polyethylene adipate glycol was heated to 87°C and mixed with maleic anhydride (19.95 g). The mixture was degassed for about 10 minutes under vacuum (>2 mm Hg). 120°C molten HQEE (14.71 g) was added to the 100°C prepolymer and mixed until uniform. The molar ratio of curing agent to isocyanate was 95%. The mixture was poured into a 120°C mold. The polyurethane was cured at 120°C for 1 hour and then post-cured at 120°C for 16 hours. The hardness of the cured polyurethane was 89A. No bubbles were observed in the molded parts.

Claims

1. A polyurethane-forming composition comprising: a) an isocyanate component, b) an isocyanate-reactive component, c) degradation agents, and d) optionally, one or more additives, wherein the isocyanate component comprises at least one of methylene-bis-(phenyl isocyanate) and toluene diisocyanate, wherein the degradation agent comprises at least one of: hexahydrophthalic anhydride, maleic anhydride, and mixtures thereof; wherein the isocyanate reactive component comprises one or more polyols, the one or more polyols comprising at least one of the following: poly(adipate) glycol, poly(hexanediol adipate) glycol, poly(ethylene adipate) glycol (PEAG), poly(diethylene adipate) glycol, poly(ethylene / propylene adipate) glycol, poly(trimethylolpropane / hexanediol adipate) glycol, poly(ethylene / butylene adipate) glycol, poly(butylene adipate) glycol, poly(hexanediol / neopentyl adipate) glycol, poly(butylene / hexanediol adipate) glycol (PBHAG), poly(neopentyl adipate) glycol, and mixtures, copolymers, and trimers thereof.

2. The polyurethane-forming composition of claim 1, wherein the stoichiometric equivalent of a) to b) is from about 80% to about 120%.

3. The polyurethane-forming composition of claim 1 or 2, wherein the stoichiometric equivalent of a) to b) is from about 85% to about 105%.

4. The composition according to any one of claims 1 to 3, wherein the degradation agent is present in an amount of about 0.20 wt% to about 30 wt% based on the sum of the isocyanate component and the isocyanate-reactive component.

5. The composition of any one of claims 1 to 4, wherein the isocyanate reactive component is a chain extender, a crosslinker, a polyol, or a combination thereof.

6. The composition of any one of claims 1 to 5, wherein the polyurethane formed by reaction of the composition has increased degradability compared to a polyurethane formed from a similar composition as described above without c) the degradation agent.

7. The composition of claim 6, wherein the increased degradability is a decrease in at least one of: (i) a mechanical property, including hardness, tensile strength, elongation, or sealing pressure; (ii) a soluble portion; (ii) a liquid portion; and (ii) a solid portion, wherein the solid portion can be broken into small pieces.

8. A polyurethane composition formed by reacting the components of the polyurethane-forming composition according to any one of claims 1 to 7.

9. A polyurethane composition comprising: The reaction product of: i) a modified prepolymer formed from a mixture of a prepolymer and a degradation agent, ii) a chain extender, and iii) optionally one or more additives, wherein the prepolymer is formed by the reaction of a diisocyanate and a polyol, wherein the diisocyanate comprises at least one of methylene-bis-(phenyl isocyanate) and toluene diisocyanate, wherein the degradation agent comprises at least one of: hexahydrophthalic anhydride, maleic anhydride, and mixtures thereof; wherein the polyol comprises at least one of poly(adipate) glycol, poly(hexanediol adipate) glycol, poly(ethylene adipate) glycol (PEAG), poly(diethylene adipate) glycol, poly(ethylene / propylene adipate) glycol, poly(trimethylolpropane / hexanediol adipate) glycol, poly(ethylene / butylene adipate) glycol, poly(butylene adipate) glycol, poly(hexanediol / neopentyl adipate) glycol, poly(butylene / hexanediol adipate) glycol (PBHAG), poly(neopentyl adipate) glycol, and mixtures, copolymers, and terpolymers thereof.

10. The polyurethane composition of claim 9, wherein the polyol and the diisocyanate have an NCO:OH ratio in the range of about 2:1 to about 20:

1.

11. The polyurethane composition of claim 9 or 10, wherein the prepolymer contains less than 0.1 wt% unreacted diisocyanate monomer and contains at least about 60% of the theoretical NCO content for a pure ABA structure.

12. The polyurethane composition according to any one of claims 9 to 11, wherein the chain extender comprises 1,4-butanediol; 1,3-propylene glycol; ethylene glycol; 1,6-hexanediol; hydroquinone-bis-hydroxyethyl ether; resorcinol di(β-hydroxyethyl) ether; resorcinol di(β-hydroxypropyl) ether; 1,4-cyclohexanedimethanol; aliphatic triol; aliphatic tetraol; 4,4'-methylenebis(2-chloroaniline); 4,4'-methylene-bis(3-chloro-2,6-diethylaniline); diethyltoluenediamine; tert-butyltoluenediamine; dimethylthiotoluenediamine; propylene glycol di-p-aminobenzoate; methylenedianiline; methylenedianiline-sodium chloride complex; and mixtures thereof.

13. An article comprising the composition according to any one of claims 8 to 12.

14. The article of claim 13, wherein the article is a pumpable tool, including a plug, a direct connect plug, a bridge plug, a wiper plug, a frac plug, an assembly of frac plugs, a drilled sand control bead screen plug, an inflow control device plug, a polymer plug, a hidden wiper plug, a cementing plug, a ball, a steering ball, a shift and positioning ball, a wiper element protector, a buoyancy recorder, a pumpable collet, a float shoe, or a dart.

15. The article of claim 13 or 14, wherein the article is a flow suppression tool, including a seal, a high pressure bead fracturing screen plug, a screen-based pipe plug, a coating for a ball and a seat, a compression seal element, an expandable seal element, an O-ring, an attachment seal, a bullet seal, a subsurface safety valve seal, a subsurface safety valve flapper seal, a dynamic seal, a V-ring, a support ring, a drill bit seal, a liner port plug, a large air disk, a large air chamber disk, a debris barrier, a drill bit energized liner plug, an inflow control device plug, a flapper, a seat, a ball seat, a direct connection disk, a drill-in linear disk, a gas lift valve plug, a fluid loss prevention flapper, an electric submersible pump seal, a shear plug, a flapper valve, a gas lift valve, or a sleeve.

16. A method for degrading degradable polyurethane, include: There is provided an article comprising the composition of any one of claims 8 to 12, subjecting the article to an aqueous, non-aqueous and / or thermal environment between 25° C. and about 350° C., or a combination thereof, The subjecting step results in a reduction in one or more of the following: (i) mechanical properties, including one or more of hardness, tensile strength, elongation and / or sealing pressure of the article; (ii) a soluble portion; (ii) a liquid portion; or (ii) a solid portion, wherein the solid portion can be broken into small pieces.

17. A method for producing a degradable article according to any one of claims 8 to 12, include: At least one of hot casting, cold casting, compression molding, injection molding or machining steps.

18. A method for producing the article of claim 8, wherein the c) degradation agent is added to the a) isocyanate component prior to the addition of the b) isocyanate reactive component.

19. A method for producing the article according to claim 8, wherein the a) isocyanate component, the b) isocyanate reactive component and the c) degradation agent are added simultaneously.

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