Microcapsules containing amines and methods for their preparation

Abstract

The present application relates to a kind of microcapsules containing amine, it includes a liquid core material and a polymer shell material, polymer shell material includes acrylonitrile-butadiene-styrene (ABS) or the composite of ABS and polyurea and its analogs, and the polymer shell material surrounds liquid core material.The content ratio of liquid core material and the content of the polymer shell material is 1:1-5:1, the ABS encapsulates the liquid core material and forms a first core-shell structure, by instant interfacial polymerization to the liquid core material and diisocyanate and its analogs forms a second core-shell structure.The shell of second core-shell structure is acrylonitrile-butadiene-styrene and / or polyurea and its analog shell, and the core of second core-shell structure is amine liquid or alcohol core material.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Patent Application No. 63 / 390,613, filed July 19, 2022, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention generally relates to technical fields such as solvent evaporation technology, interfacial polymerization, and encapsulation technology. Background Technology

[0004] Cellular compartments typically comprise membrane-sealed structures. These membrane-sealed structures establish physical boundaries to separate incompatible chemical reactions, accommodate inclusions, and regulate efficient mass transfer. Similar to cellular systems, the partitioning of active substances from inactive precursors into artificial cells, such as microcapsules and micelles, has also garnered significant interest and progress in the development of smart materials with integrated functionality and enhanced material compatibility. Among all active substances, hydrophilic loadings such as amines, alcohols, and acids are crucial for industrial applications. Specifically, polyamines with multiple amine groups have attracted considerable interest due to their low cost, wide variety, and high reactivity to many functional groups, making them ideal adsorbents for acidic gas treatment and curing agents for various groups such as epoxides and isocyanates. Therefore, many applications, from climate change to aerospace engineering, can be realized through customized amine microcapsule systems. However, despite decades of progress in research on related applications, the efficient microencapsulation of polyamines has not yet made significant strides.

[0005] In recent years, researchers have made increasing efforts in microencapsulating amines, employing various techniques. However, the main challenge in encapsulating amines is the excellent solubility of amines in water and most organic solvents, coupled with extremely high reaction kinetics. The former leads to the effective distribution of polar polyamine loadings across both emulsion phases. The high solubility of amines results in a large amount of amine being partitioned into the continuous phase, forming a thick emulsion interface, which hinders the effective adsorption of surfactant molecules to form a robust viscoelastic surfactant film. Furthermore, severe diffusion significantly promotes Oswald ripening, reducing emulsion stability and leading to uneven particle distribution, thus impeding continuous interfacial polymerization. On the other hand, the high reaction kinetics of the two monomers generate severe local kinetic turbulence, which is disastrous for the fragile surfactant film, with a high probability of emulsion rupture, resulting in interrupted shell growth and complete encapsulation failure. For these reasons, high reactivity and good solubility in most solvents make it difficult to form a stable emulsion during encapsulation, hindering the efficient encapsulation of amines.

[0006] To date, researchers in this field have explored several strategies for encapsulating hydrophilic amines, including vacuum permeation, microfluidics, and emulsion-based interfacial polymerization. For vacuum permeation, some researchers first prepare hollow microcapsules with through-pores, then permeate the amine solution into the hollow porous microcapsules with the aid of a vacuum. This method involves only physical processes and is relatively simple. However, the through-pores that facilitate amine loading can also serve as channels for easy amine release, leading to leakage of the core component during storage; therefore, microcapsules prepared by this method exhibit very low shell performance. Microfluidics are extremely inefficient and require complex equipment for microcapsule production, making them suitable only for small-scale academic research and not for industrial applications.

[0007] The third amine microcapsule production technology is based on emulsion-based interfacial polymerization, an emulsion-based method with high potential for producing polyamine microcapsules. In previous studies, researchers attempted to overcome the aforementioned obstacles by adjusting the physicochemical properties of the two emulsion phases. Partition inhibitors such as salts were used to minimize the diffusion of polyamine into the continuous phase. Polyisobutylene, a polymeric hydrocarbon additive, was added to increase the viscosity of the continuous phase by 10%. 3 This slows down the reactant delivery rate and reduces emulsion droplet coalescence. In this way, a stable emulsion can be formed for subsequent interfacial polymerization. However, due to the large amount of additives added, only microcapsules with a low effective polyamine core content (less than 50%) can be delivered.

[0008] Therefore, there is still a lack of efficient, simple, universal and scalable microencapsulation technology to prepare amine microcapsules with high core content and excellent shell properties. Summary of the Invention

[0009] Currently, there is no effective method for encapsulating hydrophilic amines in this field. The main objective of this invention is to solve these problems by exploring and developing effective strategies for scalable encapsulation of amines and to achieve ideal performance, including high core content, good shell strength, thermal stability, appropriate shell thickness, high adaptability and production efficiency.

[0010] This invention provides a controllable and scalable strategy for the microencapsulation of hydrophilic polyamines in oil-in-oil emulsion systems. The invention encapsulates hydrophilic polyamines by integrating solvent evaporation and interfacial polymerization techniques. First, the polymer is deposited at the interface via solvent evaporation, introducing a preliminary porous "membrane." In this way, the emulsion system is not necessarily thermodynamically stable, but undergoes a quasi-static process in which only the volatile solvent diffuses and evaporates stably, and the polymer continuously adjusts to the droplet volume over several hours. This highly robust system is of great interest and technically friendly in avoiding the effort required to form stable emulsions. The resulting relatively dense surface with micropores not only beneficially mitigates the vigorous transport and transfer of reactants at the interface but is also robust enough to withstand severe reaction kinetics and droplet collisions. This hybrid encapsulation technique provides new insights into the microencapsulation of unstable emulsions and has other scientific value, such as the interfacial behavior of multiphase systems and the failure modes of liquid-filled core-shell structures with thin-shell points. The large number of components that can be encapsulated using this strategy also offers promise for many industrial applications, such as coatings, potential curing agents, advanced smart materials, and gas purification.

[0011] In one aspect, the present invention provides an amine-containing microcapsule comprising a liquid core material, the liquid core material comprising an amine-containing microcapsule, the amine-containing microcapsule comprising: a liquid core material comprising an amine liquid or an alcohol and a polymer shell material. The polymer shell material comprises acrylonitrile-butadiene-styrene (ABS) or a composite of ABS and polyurea or similar substances, and the polymer shell material surrounds the liquid core material. The ratio of the liquid core material content to the polymer shell material content is 1:1 to 5:1. The ABS encapsulates the liquid core material to form a first core-shell structure, and a second core-shell structure is formed by instantaneous interfacial polymerization of the liquid core material and diisocyanate or similar substances. The shell of the second core-shell structure is an acrylonitrile-butadiene-styrene and / or polyurea or similar shell, and the core of the second core-shell structure is an amine liquid or alcohol core material.

[0012] According to one embodiment of the present invention, the amine solution comprises tetraethylenepentamine, diethylenetriamine, polyetheramine, nicotinamide, ethylenediamine, benzamide, m-phenylenediamine, triethylenetetramine, or combinations thereof, and the alcohol comprises 1,4-butanediol, ethanol, triethylene glycol, glycerol, sorbitol, xylitol, inositol, lactitol, or combinations thereof. The amine solution is highly miscible with most solvents and reactive to a wide variety of chemical groups.

[0013] According to one embodiment of the present invention, further addition of isocyanate can effectively seal micropores and enhance barrier performance. For example, diisocyanate and its analogues are selected from one or more of hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, lysine diisocyanate, polymethylene polyphenyl polyisocyanate, toluene 2,6-diisocyanate, 1,3-diisophenyl cyanate, 1,4-diisocyanate butane, terephthalic diisocyanate, 1,4-dithioisocyanate butane, or hexamethylene diisocyanate, 4,4′-bis(methylenecyclohexane) diisocyanate.

[0014] According to one embodiment of the invention, the shell thickness of the amine-containing microcapsules is in the range of 1 micrometer to 30 micrometers.

[0015] According to one embodiment of the invention, the average diameter of the amine-containing microcapsules is in the range of 45 micrometers to 300 micrometers.

[0016] According to one embodiment of the present invention, the microcapsules containing amines are spherical, elliptical, or irregular in shape.

[0017] According to one embodiment of the invention, the shell is configured to be a shell with multiple micropores (first core-shell structure) or a dense shell (second core-shell structure).

[0018] According to one embodiment of the invention, the core content loss of the amine-containing microcapsules is less than 15% during isothermal treatment at 100°C for 3 hours.

[0019] In another aspect, the present invention provides a method for preparing microcapsules containing amines, comprising:

[0020] A mixture is formed by dissolving amines or alcohols in a volatile solvent containing acetone and a shell-forming polymer of acrylonitrile-butadiene-styrene (ABS);

[0021] The mixture is emulsified in a continuous oil phase by mechanical stirring, and then the volatile solvent is evaporated by solvent evaporation to deposit ABS at the amine-paraffin oil interface to form microcapsules with a core-shell structure having multiple micropores; and

[0022] A shell-forming reactant containing diisocyanate and its analogues is added to the continuous oil phase, and interfacial polymerization is completed by interfacial polymerization to form microcapsules containing amines with a dense core-shell structure.

[0023] According to one embodiment of the present invention, the ratio of the content of amine liquid or alcohol to the content of ABS is 1:1 to 5:1.

[0024] According to one embodiment of the present invention, the volatile solvent includes acetone, dichloromethane, n-hexane, methanol, ethanol, isopropanol, ethyl acetate, or combinations thereof.

[0025] According to one embodiment of the invention, the continuous oil phase comprises oil and a surfactant, and the amine liquid and the diisocyanate and the like form a polyurea and the like shell structure through instantaneous interfacial polymerization.

[0026] According to one embodiment of the invention, the oil comprises paraffin oil and / or its analogues, wherein the paraffin oil and / or its analogues are selected from mineral oil, n-hexane, cyclohexane, hexadecane, toluene, xylene, decahydronaphthalene, or polyisobutylene, and the surfactant is selected from one or more of Span 80, Span 85, TERGITOL alkoxypolyethylene hydroxyethanol, tridecyl polyoxyethylene octadecyl ether, sodium dodecylbenzene sulfonate, 2-ethylhexanol EO-PO, polyvinyl alcohol, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, or polyethoxylated sorbitol.

[0027] According to one embodiment of the present invention, the diisocyanate and its analogues are selected from one or more of hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, lysine diisocyanate, polymethylene polyphenyl polyisocyanate, toluene 2,6-diisocyanate, 1,3-diisophenyl cyanate, 1,4-diisocyanate butane, terephthalic diisocyanate, 1,4-dithioisocyanate butane, or hexamethylene diisocyanate, 4,4′-bis(methylenecyclohexane) diisocyanate. Attached Figure Description

[0028] The invention will be more readily understood from the following description of exemplary embodiments set forth with reference to the accompanying drawings, in which:

[0029] Figure 1 A schematic diagram of the encapsulation process and real-time images tracked by an optical microscope are depicted.

[0030] Figure 2A An emulsion formed after 45 minutes of emulsification during the TEPA encapsulation process, according to an embodiment of the present invention, is shown.

[0031] Figure 2B An embodiment of the present invention is shown, in which ABS-TEPA microcapsules are deposited after solvent evaporation.

[0032] Figure 2C An embodiment of the invention is shown, in which ABS / PU-TEPA microcapsules are formed after an interfacial polymerization process.

[0033] Figure 2D A dried ABS / PU-TEPA microcapsule is shown according to an embodiment of the present invention.

[0034] Figure 3 The average particle size changes over time during the evaporation process.

[0035] Figure 4 SEM images of ABS-TEPA and ABS / PU-TEPA microcapsules are shown according to an embodiment of the present invention.

[0036] Figure 5 The FTIR curves of the extracted core material and pure TEPA are depicted according to an embodiment of the present invention.

[0037] Figure 6 The microcapsule sizes were depicted at different stirring speeds during the first stage of encapsulation.

[0038] Figure 7 An embodiment of the invention is depicted, wherein Figure 7 a is a complete image of ABS-TEPA microcapsules with different TEPA:ABS ratios (1:1–5:1). Figure 7 b is a cross-sectional image of ABS-TEPA microcapsules with different TEPA:ABS ratios (1:1–5:1), and Figure 7 c is an image showing the shell thickness of ABS-TEPA microcapsules with different TEPA:ABS ratios (1:1–5:1).

[0039] Figure 8A An optical image of a TEPA-loaded microcapsule under compression testing is shown, according to an embodiment of the invention.

[0040] Figure 8B SEM images of compressed ABS-TEPA microcapsules prior to catastrophic failure are shown, according to an embodiment of the present invention.

[0041] Figure 8C Typical stress-strain curves for single microcapsule compression tests of ABS-TEPA microcapsules according to an embodiment of the present invention are depicted.

[0042] Figure 8D The compressive strength of TEPA microcapsules with ABS shells, ABS / PU shells, and PU shells was described.

[0043] Figure 9 The results of thermal analysis of pure TEPA, microcapsule shells, and ABS-TEPA and ABS / PU-TEPA (5) microcapsules with different TEPA:ABS ratios are presented.

[0044] Figure 10 The normalized viscosity of epoxy resin monomers containing microcapsules of pure TEPA, ABS-TEPA (5), and ABS / PU-TEPA (5) at stoichiometric ratios is depicted according to an embodiment of the present invention. The inset shows the mixture under an optical microscope at the time of the last viscosity measurement. Scale bar = 200 micrometers.

[0045] Figure 11 The remaining weight of ABS-TEPA (5), pure TEPA and ABS / PU-TEPA (5) microcapsules during isothermal treatment at 100°C for 180 minutes is depicted according to an embodiment of the present invention.

[0046] Figure 12 The thermal behavior and core content changes of ABS-TEPA (5) and ABS / PU-TEPA (5) microcapsules on days 0, 30 and 60 are depicted according to an embodiment of the present invention.

[0047] Figure 13A The complete process of diethylenetriamine (DETA) encapsulation is shown, including (a1) initial emulsification, (a2) solvent evaporation, and (a3) ​​interfacial polymerization. Scale bar = 200 micrometers.

[0048] Figure 13B The complete process of 1,4-butanediol (BDO) encapsulation is shown, including (a1) initial emulsification, (a2) solvent evaporation, and (a3) ​​interfacial polymerization. Scale bar = 200 micrometers.

[0049] Figure 14A SEM images of ABS-DETA (5), ABS / PU-DETA (5), ABS-BDO (5) and ABS / PU-BDO (5) microcapsules according to an embodiment of the present invention are shown.

[0050] Figure 14B The thermal properties of DETA microcapsules according to one embodiment of the present invention are described.

[0051] Figure 14C The thermal properties of BDO microcapsules according to one embodiment of the present invention are described.

[0052] Figure 15 The CO2 capture process, CO2 uptake capacity, and amine efficiency of pure TPEA and ABS-TEPA microcapsules were demonstrated.

[0053] Figure 16The instant adhesive formulated with hexamethylene diisocyanate (HDI) microcapsules and ABS / PU-TEPA (5) microcapsules and its shear strength on different substrates are depicted. Scale bar = 2.5 cm. Detailed Implementation

[0054] In the following description, examples of core-shell microcapsules, combined solvent evaporation techniques, interfacial polymerization, and methods for encapsulating hydrophilic amines will be illustrated. Modifications, additions, and / or substitutions will not depart from the scope and spirit of the invention, and therefore the scope of the invention is not limited thereto. Specific details may be omitted to avoid obscuring the invention; however, this disclosure is prepared to enable those skilled in the art to implement the techniques disclosed herein without requiring extensive experimentation.

[0055] In addition to being physically separated into distinct microenvironments for efficient function, cells or subcellular components also communicate via cell membranes and walls. Cell membranes, bound to channel proteins, regulate the orderly entry and exit of solutes (ions or small molecules) to maintain cellular activity. These substances can only be transported or exchanged in a controlled manner and at controlled rates under specific conditions, such as concentration gradients, temperature, and energy input. Furthermore, the cell membrane connects to the cytoskeleton or is integrally attached to the cell wall, providing structural support and mechanical resistance to prevent deformation. Inspired by these cellular characteristics, this invention provides a porous membrane to regulate reactant transport to control the reaction kinetics of shell formation. This "membrane" or "wall" is sufficiently robust to withstand severe impacts and disturbances during emulsification and interfacial polymerization processes.

[0056] Amine groups possess immense potential as ideal carbon dioxide adsorbents and multifunctional curing agents, suitable for a wide range of adhesives in high-end industrial applications. Inspired by the widespread existence of cellular systems, where physical boundaries (e.g., membrane structures) are established to accommodate internal substances and regulate efficient mass transfer to ensure effective operation, encapsulating amines into microstructures facilitates the design of intelligent material systems with high adaptability, controllability, and efficiency.

[0057] This invention utilizes the rapid reaction kinetics of amines and diisocyanates to provide an amine-containing microcapsule comprising a liquid core material and a polymer shell material. The polymer shell material includes acrylonitrile-butadiene-styrene (ABS) or a composite of ABS and polyurea or similar substances, and the polymer shell material surrounds the liquid core material. The content ratio of the liquid core material to the polymer shell material is 1:1 to 5:1. The ABS encapsulates the liquid core material to form a first core-shell structure, and a second core-shell structure is formed by instantaneous interfacial polymerization of the liquid core material and diisocyanate or similar substances. The shell of the second core-shell structure is an acrylonitrile-butadiene-styrene and / or polyurea or similar substances, while the core of the second core-shell structure is an amine liquid or an alcohol-based core material.

[0058] According to one embodiment of the present invention, the amine-containing microcapsules are spherical, elliptical, or irregular in shape.

[0059] In this invention, the range of contents of the liquid core material can be adjusted according to specific application requirements. In some embodiments, the contents of the liquid core material can vary within a specific range of chemical compositions to obtain the desired material properties. These chemical compositions may include a single substance or a combination of multiple substances to achieve the desired performance and properties. According to one embodiment of the invention, the liquid core material includes, but is not limited to, hydrophilic amines or amines with long hydrocarbon chains, such as tetraethylenepentamine, diethylenetriamine, or combinations thereof.

[0060] In other embodiments, the liquid core material includes alcohols, including but not limited to 1,4-butanediol, ethanol, triethylene glycol, glycerol, sorbitol, xylitol, inositol, and lactitol.

[0061] According to one embodiment of the present invention, the ratio of the liquid core material content to the polymer shell material content is 1:1 to 5:1. For example, the ratio of the liquid core material content to the polymer shell material content is 1:1, 2:1, 3:1, 4:1, or 5:1.

[0062] According to one embodiment of the invention, the shell thickness of the amine-containing microcapsules is in the range of 1 micrometer to 30 micrometers. A thicker shell thickness (approximately 5 to 30 micrometers) is achieved when the TEPA:ABS ratio is low, and a thinner shell thickness (less than 5 micrometers) is achieved when the TEPA:ABS ratio is high.

[0063] According to one embodiment of the present invention, the diisocyanate and its analogues include, but are not limited to, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, lysine diisocyanate, polymethylene polyphenyl polyisocyanate, toluene 2,6-diisocyanate, 1,3-diisophenyl cyanate, 1,4-diisocyanate butane, terephthalic diisocyanate, 1,4-dithioisocyanate butane, hexamethylene diisocyanate, or 4,4′-bis(methylenecyclohexane) diisocyanate, etc.

[0064] According to one embodiment of the invention, the average diameter of the amine-containing microcapsules is in the range of 45 micrometers to 300 micrometers. For example, the average diameter of the amine-containing microcapsules may be 50 micrometers, 75 micrometers, 100 micrometers, 125 micrometers, 150 micrometers, 175 micrometers, 200 micrometers, 225 micrometers, 250 micrometers, 275 micrometers, or 300 micrometers.

[0065] According to one embodiment of the invention, the core content loss of the amine-containing microcapsules is less than 15% during isothermal treatment at 100°C for 3 hours.

[0066] In another aspect, the present invention provides a method for preparing microcapsules containing amines, comprising:

[0067] A mixture is formed by dissolving amines or alcohols in a volatile solvent containing acetone and a shell-forming polymer of acrylonitrile-butadiene-styrene (ABS);

[0068] The mixture is emulsified in a continuous oil phase by mechanical stirring, and then the volatile solvent is evaporated to deposit ABS at the amine-paraffin oil interface to form microcapsules with a core-shell structure having multiple micropores; and

[0069] A shell-forming reactant containing diisocyanate and its analogues is added to the continuous oil phase, and interfacial polymerization is completed by interfacial polymerization to form microcapsules containing amines with a dense core-shell structure.

[0070] According to one embodiment of the invention, the amine solution and the diisocyanate and its analogues form a polyurea and / or its analogue shell structure through instantaneous interfacial polymerization. "Instantaneous interfacial polymerization" involves the reaction of the amine solution and the diisocyanate (or its analogue), during which the reaction occurs at the interface where the two substances meet due to the rapid reaction rate of the amine solution and the diisocyanate. The rapidity of this interfacial polymerization reaction allows the polymer material to be formed and bonded at the interface in a short time.

[0071] According to one embodiment of the present invention, the volatile solvent includes, but is not limited to, acetone, dichloromethane, n-hexane, methanol, ethanol, isopropanol, and ethyl acetate.

[0072] According to one embodiment of the present invention, the continuous oil phase comprises oil and a surfactant. The oil includes, but is not limited to, paraffin oil and / or its analogues, which may be mineral oil, one or more of n-hexane, cyclohexane, hexadecane, toluene, xylene, decahydronaphthalene, or polyisobutylene. The surfactant is, but is not limited to, Span 80, Span 85, TERGITOL alkoxyethylene hydroxyethanol, tridecyl polyoxyethylene octadecyl ether, sodium dodecylbenzenesulfonate, 2-ethylhexanol EO-PO, polyvinyl alcohol, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, or polyethoxylated sorbitol oleate.

[0073] According to one embodiment of the present invention, the diisocyanate and its analogues, but not limited to, hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, lysine diisocyanate, polymethylene polyphenyl polyisocyanate, toluene 2,6-diisocyanate, 1,3-diisophenyl cyanate, 1,4-diisocyanate butane, terephthalic diisocyanate, 1,4-dithioisocyanate butane, or hexamethylene diisocyanate, 4,4′-bis(methylenecyclohexane) diisocyanate, are one or more of these.

[0074] Preferably, the diisocyanate and its analogues include 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, lysine diisocyanate, polymethylene polyphenyl polyisocyanate, toluene 2,6-diisocyanate, 1,3-diisophenyl cyanate, 1,4-diisocyanate butane, terephthalic diisocyanate, 1,4-dithioisocyanate butane, or hexamethylene diisocyanate, etc.

[0075] According to one embodiment of the invention, the stirring rate is from 200 rpm to 500 rpm. For example, the stirring rates are 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm.

[0076] Example

[0077] Example 1 - Preparation of ABS-TEPA microcapsules and ABS / PU-TEPA microcapsules

[0078] The synthesis of microcapsules mainly consists of two steps: First, an acrylonitrile-butadiene-styrene (ABS) copolymer shell is deposited by solvent evaporation to obtain ABS-TEPA microcapsules. Second, a polyurea (PU) shell is further coated onto the ABS-TEPA microcapsules by interfacial polymerization to obtain ABS / PU-TEPA microcapsules.

[0079] The solvent evaporation process is a physical process. First, 1.5 g of tetraethylenepentamine (TEPA), 20.0 g of acetone, and a certain amount of ABS polymer (which varies depending on the specified TEPA:ABS ratio) are uniformly mixed as the dispersed phase. Then, the mixture is transferred to a 250 mL beaker containing 60.0 g of paraffin oil and 0.3 g of the linear nonionic surfactant tergitol. TM The mixture was stirred at 300 rpm. The system can be operated at room temperature. The first stage was completed after 12 hours of evaporation, yielding ABS-TEPA microcapsules. Subsequently, an interfacial polymerization stage was carried out, with the second stage achieved by directly adding 6.0 g of 4,4'-dicyclohexylmethane diisocyanate (HMDI) to the above system. The system was reacted in a water bath at 40°C for 2 hours, at 50°C for 2 hours, and at 60°C for 1 hour to obtain ABS / PU-TEPA microcapsules. Finally, the ABS / PU-TEPA microcapsules were washed with n-hexane, dried in a fume hood for 20 minutes, and subjected to further analysis. The same washing and drying procedure was followed when collecting the ABS-TEPA microcapsules.

[0080] Reference Figure 1 The timeline of microcapsule formation was monitored and recorded using optical microscopy. Initially, translucent, uniform droplets were observed during emulsification. As acetone evaporated, a shell began to form, the droplets became opaque, and ABS-rich acetone microspheres separated from the original droplets. Due to anchoring, the flowing ABS-rich microspheres tended to deposit at the emulsion interface. These microspheres were initially individually anchored at the interface. With further solvent removal, the ABS microsphere deposit became thicker. The polymer microspheres at the interface were not completely desolvated before the final trace acetone evaporation. Movable, expanding ABS particles diffused and fused with neighboring particles, engulfing the TEPA / acetone droplets. Finally, when all the acetone had evaporated, completing the first encapsulation step, the ABS solidified into a porous shell. Further interfacial polymerization could then seal the micropores in the membrane, yielding ABS / PU-TEPA microcapsules.

[0081] The first encapsulation step is a physical reaction process. As acetone gradually diffuses and evaporates, the ABS-rich microspheres gradually migrate and adjust themselves to adapt to the changes in droplet volume. Throughout the dozen or so hours of changes in the ABS shell coating the droplets, the polyamine emulsion does not face any sudden disturbances, allowing for the next encapsulation step. This transient quasi-equilibrium process is particularly ideal for encapsulating fragile non-aqueous emulsions, as they are typically difficult to stabilize thermodynamically.

[0082] Figure 2A-2BThe appearance of the ABS-TEPA microcapsules before and after the solvent evaporation process is shown. Due to instability during the encapsulation process, irregularly shaped microcapsules are formed. Surprisingly, even with solvent evaporation and a reduction in the total core content, the size of the collected final ABS-TEPA shell-structured microcapsules is no smaller than that of the parent emulsion droplets. Figure 2B This phenomenon is likely due to Oswald curing and emulsion coalescence. TEPA, with its relatively high diffusivity, diffuses into paraffin more readily, resulting in a more pronounced Oswald curing effect than aqueous emulsions. Furthermore, droplet coalescence also leads to particle size deviations, as evidenced by the occasional appearance of peanut-shaped microcapsules. Figure 2B ). Figure 2C-2D The images show the appearance of ABS / PU-TEPA microcapsules after further interfacial polymerization of the ABS-TEPA shell-structured microcapsules and their dried state. As can be seen from the images, the microcapsules are spherical, elliptical, or irregular in shape. Due to the instability of the emulsion, the average size of the emulsion droplets increases during the first 5 hours of evaporation, but the particle size does not change significantly from 5 hours to 20 hours. Figure 3 It is worth noting that, unlike previous methods that sacrificed effective core content to ensure emulsion stability, this instability and deviation did not interfere with the successful production of ABS-TEPA microcapsules, which in turn demonstrates the superiority of this emulsion system over other methods: it exhibits high tolerance.

[0083] Reference Figure 4 Above, after the first stage of encapsulation, ABS-TEPA microcapsules were collected and observed using a scanning electron microscope. The image shows that the spherical microcapsules have a clear core-shell structure, a relatively smooth surface, and discrete micropores. The shell thickness is somewhat uneven. This may be because the evaporation rate did not allow the polymer sufficient time to fully relax and fuse, leading to partial aggregation of the ABS microspheres. (Reference) Figure 4 Below, after the solvent evaporation process is complete, an interfacial polymerization reaction is carried out by directly adding 4,4'-dicyclohexylmethane diisocyanate (HMDI), forming a dense and highly compact polyurea (PU) shell. As can be seen from the figure, the shell of the ABS / PU-TEPA microcapsules is denser than that of the ABS-TEPA microcapsules. Compared to the mandatory requirement for the slow addition of HMDI to the emulsion in other methods, the direct addition of HMDI does not cause significant damage to the existing system. The microporous membrane effectively mitigates the violent transfer of reactants at the interface.

[0084] On the other hand, the ABS skeleton gives the membrane material high strength and toughness to resist catastrophic deformation caused by rapid reaction dynamics and droplet collisions.

[0085] During the second-stage encapsulation process, the ABS / PU-encapsulated TEPA (ABS / PU-TEPA) microcapsules maintained essentially the same integrity as in the first stage. Fragments were formed due to the reaction of dissolved TEPA and HMDI in the continuous phase but were easily washed away by the solvent. The core material extracted after the interfacial reaction exhibited the same Fourier transform infrared (FTIR) spectrum as the group using only TEPA, indicating successful encapsulation. Figure 5 Following interface polymerization, the microcapsules largely retained their original shape and core-shell structure. The outer surface of the structure became more dense, while the inner surface remained largely unchanged. Figure 4 This is because TEPA diffuses outward at the interface and reacts with HMDI, which has completed interfacial polymerization. Therefore, the reaction zone is mainly located near the outer surface of the ABS layer. During the reaction, reactants are continuously transported to the interface, and when they meet, a polyurea shell immediately forms, hindering further molecular contact and reaction. This self-limiting characteristic of interfacial polymerization results in a relatively thin shell. Therefore, the overall shell thickness does not change significantly after the second stage of reaction, but the compactness is improved. Furthermore, indentations occur on the structural surface due to the collapse of microcapsules at the thin shell caused by the consumption of the TEPA core during interfacial polymerization.

[0086] Example 2 - Optimization of microcapsule size, shell thickness, shell strength, and core content

[0087] Microcapsules of different diameters can be obtained by adjusting the stirring rate during the first-stage solvent evaporation process. Adjusting the stirring rate between 200 rpm and 500 rpm yields microcapsules with average diameters ranging from approximately 45 micrometers to approximately 300 micrometers. Figure 6 ).

[0088] Furthermore, this invention also found that the TEPA:ABS mass ratio is crucial because it is directly related to the theoretical core content and may be related to the shell thickness. In this example, microcapsules with TEPA:ABS ratios ranging from 1:1 to 5:1 were prepared and studied. Figure 7 As shown in (a), these microcapsules are generally identical in appearance, but differ significantly in internal structure and shell thickness. Figure 7(b) Cross-sections of ABS-TEPA microcapsules with different TEPA:ABS ratios. The figure shows that microcapsules with a 1:1 ratio have a multinucleated internal structure, while microcapsules with ratios higher than 1:1 (2:1, 3:1, 4:1, and 5:1) have a mononucleated internal structure. When the TEPA:ABS ratio decreases to 1:1, the internal structure changes from a mononucleated shape to a multinucleated porous structure. This is likely due to the restricted movement of polymer chains at higher outer shell polymer concentrations. In this example, the co-solvent acetone and the core component TEPA content were kept constant, and only the TEPA:ABS ratio was varied. The results show that at a low ratio (1:1), the polymer concentration is very high, and this combination approaches a bisection curve in the polymer region of the phase diagram. As acetone evaporates, high-viscosity droplets form. This high viscosity kinetically hinders the movement of polymer particles. Therefore, the acetone completely evaporates before the ABS polymer can migrate and diffuse at the interface, resulting in a porous and almost continuous internal structure.

[0089] Furthermore, the shell thickness of ABS-TEPA microcapsules decreases as the TEPA:ABS ratio increases. Figure 7 (c) The shell thickness decreases with increasing TEPA:ABS ratio because less ABS polymer is deposited at the interface.

[0090] Furthermore, core-shell microcapsules also exhibit a hierarchical shell structure. Although the surface of microcapsules prepared under all conditions displays a relatively smooth and porous exterior, the interior is even more porous, with microbeads always dotting the innermost layer. This can also be explained by the kinetic constraint on the movement of polymer chains, as the viscosity of polymer particles increases the later they separate. Therefore, the particles solidify before they can diffuse and fuse uniformly, leaving behind a highly porous internal shell structure, or even forming solid beads.

[0091] Figure 8A Optical images of TEPA-loaded microcapsules under compression testing are shown. (Reference) Figure 8C Group ABS-TEPA(1) represents ABS-TEPA microcapsules with a TEPA:ABS ratio of 1:1. Group ABS-TEPA(2) represents ABS-TEPA microcapsules with a TEPA:ABS ratio of 2:1. Group ABS-TEPA(3) represents ABS-TEPA microcapsules with a TEPA:ABS ratio of 3:1. Group ABS-TEPA(4) represents ABS-TEPA microcapsules with a TEPA:ABS ratio of 4:1. Group ABS-TEPA(5) represents ABS-TEPA microcapsules with a TEPA:ABS ratio of 5:1.

[0092] In the compression test of individual microcapsules, the mechanical resistance increased significantly as the TEPA:ABS ratio decreased. For ABS-TEPA (1) microcapsules with a 1:1 ratio, where the microcapsule contains continuous solid microbeads, the load exceeded the measurement range of the loaded cell and could not be detected. For other microcapsules, cracks first appeared at the thin shell, and then the entire structure completely ruptured. Figure 8B This is also related to... Figure 8C This is consistent with the slight decrease shown in the nominal stress-strain curve. (Refer to...) Figure 8D Besides the 1:1 composition, the strength of the ABS / PU-TEPA microcapsules ranges from 152±9 kPa to 832±15 kPa, significantly higher than that of similarly sized pure PU-coated TEPA (PU-TEPA) microcapsules (45±8 kPa). Based on this, it can be easily estimated that the contribution of the PU shell to the overall shell strength of the ABS / PU-TEPA microcapsules is almost negligible. Mechanical resistance is primarily generated by the ABS skeleton. Pure PU is extremely fragile under harsh operating conditions. This demonstrates that the ABS / PU-TEPA microcapsules of this invention are superior to most previously used PU-shell amine microcapsules.

[0093] Since the ABS shell tightly coats the surface of the core droplet, the thinning of the shell with increasing TEPA:ABS ratio indicates an increase in the proportion of the core within the microcapsule, which can also be confirmed by thermogravimetric analysis (TGA). The core content can be estimated using different decomposition temperatures from the TGA curve. Figure 9 The different decomposition temperature ranges of the TEPA core and ABS shell facilitate easy assessment of the TEPA core content of the microcapsules. The thermogravimetric curves of pure TEPA show that TEPA is completely degraded at or before 240°C, while the ABS thermogravimetric curves show that ABS begins to degrade at or above 360°C. For any ABS-TEPA microcapsule, the descending portion of the thermogravimetric curve before 240°C represents the loss due to TEPA degradation, from which the relative TEPA content, i.e., the microcapsule core content, can be obtained. By increasing the TEPA:ABS ratio, the initial ABS-TEPA microcapsule core content can be adjusted over a wide range, from approximately 33.2 wt% to approximately 75.4 wt%. During interfacial polymerization, the formation of the PU shell consumes less TEPA core, as only nanoscale PU shells are generated at the interface. Therefore, the core content of ABS / PU-TEPA microcapsules is generally kept similar to that of ABS-TEPA microcapsules.

[0094] Example 3 - Stability of microcapsules in epoxy resin

[0095] The formation of a dense PU shell enhances barrier properties. In this example, the chemical resistance of ABS-TEPA(5) and ABS / PU-TEPA(5) microcapsules in liquid epoxy monomers was evaluated. Figure 10 As can be seen, the viscosity of the mixture of pure TEPA and epoxy monomers increased dramatically within a few hours. In contrast, the epoxy resin containing ABS-TEPA(5) microcapsules increased only about 7 times in viscosity at the stoichiometric ratio after 20 days of suspension. Some voids were formed due to TEPA leakage through the micropores (as shown by the black circles). As a result, the epoxy resin was slightly cured, and its viscosity increased. However, overall, the porous ABS shell largely protected the TEPA from spreading outward. For the suspension with densely packed ABS / PU-TEPA(5) microcapsules, the viscosity only increased by about 3 times in 20 days. Due to the very limited penetration of TEPA, only a small amount of flocculent material formed around the microcapsules.

[0096] On the other hand, isothermal treatment at 100°C for 180 minutes ( Figure 11 During the period, compared with ABS-TEPA(5) microcapsules (67.9 wt%), ABS / PU-TEPA(5) microcapsules (89.0 wt%) reduced and slowed down TEPA loss. The higher TEPA loss of ABS-TEPA(5) microcapsules was mainly due to the micropores on its ABS shell causing TEPA to evaporate at a higher specific surface area.

[0097] In storage stability tests ( Figure 12 Both microcapsules remained remarkably stable in maintaining their original core content after being stored at room temperature for more than 60 days. More specifically, neither the ABS-TEPA(5) nor the ABS / PU-TEPA(5) microcapsules showed any changes in thermal behavior or core content over a period of up to 60 days, indicating excellent storage stability under ambient conditions.

[0098] Example 4 - Microcapsules encapsulating other hydrophilic core components

[0099] This invention employs a preliminary process of forming a robust porous membrane to mitigate severe mass transfer and intense reaction kinetic turbulence, followed by interfacial polymerization to improve barrier properties. This method is applicable not only to encapsulating TEPA core components but also to encapsulating many other components via solvent evaporation technology, and incorporates active hydrogen that reacts with isocyanates to complete interfacial polymerization. This strategy is particularly effective for encapsulating polar loads, which are subject to problems with unstable emulsion stability and limited encapsulation techniques.

[0100] Therefore, in this example, other amines and alcohols with different physicochemical properties were used for verification, such as diethylenetriamine (DETA) and 1,4-butanediol (BDO). Figures 13A-13B These processes were monitored using an optical microscope, and the encapsulation process of these hydrophilic core components was similar to the aforementioned TEPA encapsulation process. Group ABS-DETA(5) represents ABS-DETA microcapsules with a DETA:ABS ratio of 5:1, and group ABS-BDO(5) represents ABS-BDO microcapsules with a BDO:ABS ratio of 5:1. SEM images of ABS-DETA(5) microcapsules, ABS / PU-DETA(5), ABS-BDO(5), and ABS / PU-BDO(5) all showed spherical shapes and unique core-shell structures. Figure 14A The core contents of ABS / PU-DETA(5) microcapsules and ABS / PU-BDO(5) microcapsules, as determined by TGA, were approximately 75% and 70%, respectively. Figure 14B-14C This highlights the effectiveness of different payload packaging methods.

[0101] Example 5 - CO2 Reduction Performance Test of ABS-TEPA Microcapsules

[0102] As described above, ABS-TEPA microcapsules organize an amine core with a hierarchical shell structure at the microscale, especially when the core-polymer ratio is less than 4:1. While the less porous outer surface protects the amine payload from significant loss, the larger internal pores provide sufficient pathways for efficient CO2 transport and capture.

[0103] from Figure 15 As can be seen, there is a trade-off between adsorbent efficiency and amine efficiency. Higher ABS content helps create more carbon dioxide transport channels, thus improving amine efficiency. However, a significant reduction in TEPA content undoubtedly decreases surface adsorption efficiency. Interestingly, all ABS-TEPA microcapsules exhibited higher amine efficiencies (0.18–0.21) in CO2 capture compared to a fixed volume of liquid TEPA (0.06). Therefore, even with a certain percentage of ABS shell in the microcapsule adsorbent, their overall adsorption efficiencies (1.91–3.60 mmol g) are relatively high. -1 The levels were still significantly higher than in the pure TEPA group (1.58 mmol g). -1 ).

[0104] Example 6 - Experimental Study on Powdered PU-Based Instant Gel

[0105] The high reactivity of amines to multiple chemical groups makes them a flexible curing agent. In particular, amines are known to react rapidly with isocyanates at room temperature to form polyureas without a catalyst.

[0106] In this example, a simple mixture with hexamethylene diisocyanate (HDI) microcapsules can be used to further develop an instant adhesive. This is particularly efficient for adhesive operations, as the high reaction rates of these two chemicals typically require specialized mixing and delivery techniques to produce polyurea. By encapsulating the chemicals in micron-sized powder microcapsules, the chemicals are well preserved and easy to mix uniformly for field applications. Figure 16 As shown, this instant adhesive exhibits excellent curing speed and adhesion to all substrates, including wood, epoxy resin, aluminum, and glass. At room temperature (25°C), a 0.05g microcapsule mixture cured in 10 seconds can withstand a weight of 200g. Shear strength is calculated based on single-sided shear tensile testing. Compared to aluminum and glass, this instant adhesive shows better adhesion to wood and epoxy resin substrates due to its higher surface roughness and better chemical compatibility. Within 30 minutes of curing at room temperature, the shear strength of the instant adhesive can reach up to 50kPa. Because the polyurea reaction is insensitive to temperature and humidity and proceeds rapidly within seconds to minutes, breakthroughs in the robust encapsulation of reactants are believed to have greatly propelled the development of polyurea-based instant adhesives.

[0107] definition

[0108] Throughout this specification, unless otherwise specified, the term "comprise" or variations thereof, such as "include" or "contain," shall be understood to include a specified whole or entirety, but not to exclude the inclusion of any other whole or group of wholes. It should also be noted that in this disclosure, particularly in the claims or period, the terms "comprise," "include," or "contain" have the meaning given to them under U.S. patent law. For example, they allow for undefined elements but exclude elements found in the prior art or that affect the essential or novel features of the invention.

[0109] Furthermore, throughout the specification and claims, unless otherwise required, the term "comprising" or variations thereof shall be understood to include a specified whole or group of wholes, but not to exclude the inclusion of any other whole or group of wholes.

[0110] As used herein, the terms "substantially," "essentially," "approximately," and "about" are used to describe and explain a small variation. When used in conjunction with an event or situation, the term can refer to the exact occurrence of the event or situation, or to an approximate occurrence. For example, when used with numerical values, these terms can encompass a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

[0111] The specification uses terms such as "an embodiment," "embodiment," and "example embodiment" to indicate that the described embodiment may include specific features, structures, or characteristics. However, each embodiment need not include specific features, and these features do not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in conjunction with an embodiment, it is assumed that it is within the knowledge of those skilled in the art, and whether explicitly described or not, these features, structures, or characteristics can be applied in conjunction with other embodiments.

[0112] In the preparation methods described herein, the steps may be performed in any order without departing from the principles of the invention, unless the chronological or operational order is explicitly stated. In a claim, it should be stated that one step is performed first, followed by several other steps, meaning the first step is performed before any other steps, but the other steps may be performed in any suitable order unless the sequence is further enumerated in the other steps. For example, a claim element enumerating "steps A, B, C, D, and E" should be understood as performing step A first and step E last, with steps B, C, and D performed in any order between steps A and E, and such order remains within the literal meaning of the claim process. A given step or subset of steps may also be repeated.

[0113] The term "TEPA (Triethylenetetramine)" is an organic compound, also known as TEPA amine, which is obtained by the synthesis of four ethanolamine molecules via a cross-halogenated amine reaction. The chemical structure of TEPA contains one major amine group (NH2) and three minor amine groups.

[0114] The term "1,4-Butanediol (abbreviated as BDO)" is an organic compound with the chemical formula C4H. 10 O2. It is a colorless and odorless liquid, commonly used as a solvent, raw material, and intermediate in many industrial applications.

[0115] The term "diethylenetriamine (DETA)" is an organic compound with the chemical formula C4H13N3. It is a colorless liquid with an ammonia-like odor. DETA is a multifunctional amine with a variety of applications. In the chemical industry, it is mainly used as an intermediate and reactant in chemical synthesis. DETA is commonly used in the manufacture of resins, coatings, plastics, rubber, and other products. It plays an important role in the synthesis of polyetheramine resins, epoxy resins, urea resins, and other similar products.

[0116] In addition, DETA is widely used in water treatment, surfactants, dyes, pesticides, and other fields. It can act as a metal chelating agent for the removal of metal ions and catalytic reactions. Furthermore, DETA is used as a synthetic intermediate for certain drugs.

[0117] The foregoing briefly describes several embodiments and detailed features of this disclosure. The embodiments described in this disclosure can be readily used as the basis for designing or modifying other processes and structures to achieve the same or similar objectives introduced in the embodiments of this disclosure and / or obtain the same or similar advantages. Such equivalent structures do not depart from the spirit and scope of this disclosure, and various changes, substitutions, and modifications can be made without departing from the spirit and scope of the invention.

Claims

1. A microcapsule, characterized in that, The microcapsules include: A liquid core material, said liquid core material comprising an amine liquid; and A polymer shell material comprising acrylonitrile-butadiene-styrene or a composite of acrylonitrile-butadiene-styrene and polyurea, wherein the polymer shell material surrounds the liquid core material. The ratio of the liquid core material content to the polymer shell material content is 1:1 to 5:

1. The acrylonitrile-butadiene-styrene encapsulates the liquid core material to form a first core-shell structure, and an instantaneous interfacial polymerization of the liquid core material and diisocyanate forms a second core-shell structure. The shell of the second core-shell structure is acrylonitrile-butadiene-styrene and polyurea, and the core of the second core-shell structure is an amine liquid.

2. The microcapsule according to claim 1, wherein the amine liquid comprises tetraethylenepentamine, diethylenetriamine, polyetheramine, ethylenediamine, m-phenylenediamine, triethylenetetramine, or a combination thereof.

3. The microcapsule according to claim 1, wherein the diisocyanate is selected from one or more of hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, lysine diisocyanate, toluene 2,6-diisocyanate, 1,3-diisophenylcyanate, terephthalic diisocyanate, hexamethylene diisocyanate, and 4,4′-bis(methylenecyclohexane) diisocyanate.

4. The microcapsule according to claim 1, wherein the shell thickness of the microcapsule is in the range of 1 micrometer to 30 micrometers.

5. The microcapsule according to claim 1, wherein the average diameter of the microcapsule is in the range of 45 micrometers to 300 micrometers.

6. The microcapsule according to claim 1, wherein the microcapsule is spherical, elliptical, or irregular in shape.

7. The microcapsule according to claim 1, wherein the shell is configured to have a plurality of micropores or a dense shell.

8. The microcapsule according to claim 1, wherein the core content loss of the microcapsule is less than 15% during isothermal treatment at 100°C for 3 hours.

9. A method for preparing microcapsules according to claim 1, characterized in that, The method includes: The amine solution is dissolved in a volatile solvent containing acetone and a shell-forming polymer of acrylonitrile-butadiene-styrene, thereby forming a mixture; The mixture is emulsified in a continuous oil phase by mechanical stirring, and then the volatile solvent is evaporated by solvent evaporation to deposit acrylonitrile-butadiene-styrene at the amine-paraffin oil interface to form microcapsules with a core-shell structure having multiple micropores; and A shell-forming reactant containing diisocyanate is added to the continuous oil phase, and interfacial polymerization is completed by interfacial polymerization to form microcapsules with a dense core-shell structure.

10. The method according to claim 9, wherein the ratio of the content of the amine liquid to the content of the acrylonitrile-butadiene-styrene is 1:1 to 5:

1.

11. The method according to claim 9, wherein the amine liquid comprises tetraethylenepentamine, diethylenetriamine, polyetheramine, ethylenediamine, m-phenylenediamine, triethylenetetramine, or a combination thereof.

12. The method of claim 9, wherein the volatile solvent further comprises dichloromethane, n-hexane, methanol, ethanol, isopropanol, ethyl acetate, or a combination thereof.

13. The method of claim 9, wherein the continuous oil phase comprises oil and a surfactant.

14. The method of claim 13, wherein the oil comprises paraffin oil selected from mineral oil, n-hexane, cyclohexane, hexadecane, toluene, xylene, decahydronaphthalene, or polyisobutylene, and the surfactant selected from Span 80, Span 85, TERGITOL alkoxyethylene hydroxyethanol, tridecyl polyoxyethylene octadecyl ether, sodium dodecylbenzene sulfonate, 2-ethylhexanol EO-PO, polyvinyl alcohol, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, or polyethoxylated sorbitol.

15. The method according to claim 9, wherein the diisocyanate is selected from one or more of hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, lysine diisocyanate, toluene 2,6-diisocyanate, 1,3-diisophenyl cyanate, 1,4-diisocyanate butane, terephthalic diisocyanate, hexamethylene diisocyanate, and 4,4′-bis(methylenecyclohexane) diisocyanate.

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