Debondable adhesive

Abstract

A debondable adhesive formulation comprising a multifunctional polymer having programmable bonds made from a Diels-Alder adduct and a concentration of a diene trapping agent. The programmable bonds include one or more diene-dienophile pairs capable of forming a Diels-Alder adduct. The debondable adhesive formulation can be applied as a coating. The debondable adhesive formulation can be extruded. The debondable adhesive formulation has a bonding temperature of 30°C to 150°C and a debonding temperature of 130°C or greater. When the debondable adhesive formulation is at or above the debonding temperature, at least a portion of one or both of the programmable bonds and the diene-diene trapping adduct dissociate and the adhesive bond strength is reduced. The adhesive formulation includes non-programmable bonds that do not dissociate at the debonding temperature.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 592,412, filed October 23, 2023, the entire contents of which are incorporated herein by reference. Background Technology

[0002] In manufacturing environments, adhesives are widely used to bond materials together. The ease of application over large areas reduces labor costs and makes bonds more durable. Different types of polymers have been used to manufacture adhesive systems. Epoxy resins, siloxanes, modified siloxanes, acrylic resins, cellulose resins, vinyl esters, polyurea, polyurethanes, and phenolic nitrile systems are some of the basic resin systems used in adhesive formulations. The choice of base material system is usually based on performance requirements and the substrate to be bonded. However, a problem with existing adhesive systems is that they are not prone to failure or detachment at the end of the product's life, thus hindering the reuse of valuable product components.

[0003] Therefore, there is a need to develop an adhesive that can be readily used for manufacturing purposes, is durable throughout the product's lifespan, and can be easily debonded or detached at the end of its lifespan using selected stimuli. This approach enables the reuse and recycling of high-value components in products. Furthermore, it simplifies the rework and repair of durable consumer goods, thereby saving costs for manufacturers. This invention provides such a debondable adhesive. Summary of the Invention

[0004] In a first aspect of the invention, a detackable adhesive formulation comprises a multifunctional polymer having programmable linkages formed from a Diels-Alder adduct and a certain concentration of a diene trap. The programmable linkages comprise one or more diene-diene pairs capable of forming the Diels-Alder adduct. The diene trap is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene trap adduct, which remains stable until dissociation at the detackable temperature of the adhesive, wherein the molar number of the diene trap exceeds the molar number of one or more dienes. The detackable adhesive formulation can be used as a coating. The detackable adhesive formulation can be extruded. The bonding temperature of the detackable adhesive formulation is from 30°C to 150°C, and the detackable temperature is 130°C or higher. When the detackable adhesive formulation is at or above the detackable temperature, at least a portion of one or both of the programmable linkages and the diene-diene trap adduct dissociates, and the adhesive strength decreases. Adhesive formulations include non-programmable bonds that do not dissociate at debonding temperatures. Attached Figure Description

[0005] The foregoing aspects and other features of this disclosure are explained in the following description, in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of an exemplary thermosetting system. Figure 1 In this context, the term "p" represents monomer conversion rate. c "Represents the critical gelation conversion rate at which the network begins to form, but still has sufficient long-range motion to obtain processable material. Large spheres represent multifunctional polymers, oligomers, or molecules (functionality greater than or equal to 2.0). Small spheres represent bifunctional polymers, oligomers, or molecules (functionality equal to 2.0). Large spheres have the function of reacting with small spheres to form covalent or dative bonds, linking the components together."

[0006] Figure 2 This is a schematic diagram illustrating the interconversion of Diels-Alder adducts as temperature and curing state increase.

[0007] Figure 3 This is a diagram illustrating the forward and reverse Diels-Alder reactions for each adduct. Figure 3 In the diagram, the overlay represents the temperature range where the processing, bonding, and debonding steps occur. Detailed Implementation

[0008] To facilitate an understanding of the principles of this disclosure, reference will now be made to preferred embodiments, and these preferred embodiments will be described using specific language. However, it should be understood that this is not intended to limit the scope of this disclosure, and such changes and further modifications to this disclosure as illustrated herein are considered to be commonly apparent to those skilled in the art to which this disclosure pertains.

[0009] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0010] As used herein, the terms “including,” “comprising,” or “having,” and variations thereof, mean to include the elements listed thereafter and their equivalents, as well as any additional elements. As used herein, “and / or” refers to and includes all possible combinations of one or more of the related listed items, as well as any combinations missing when interpreted in the context of substitution (“or”).

[0011] Furthermore, the indefinite articles “a” and “an” preceding an element or component of the present invention are not intended to limit the number of times the element or component appears. Therefore, “a” and “an” should be understood to include one or at least one, and unless the number is explicitly singular, the singular form of the element or component also includes the plural form.

[0012] This invention addresses the need for adhesives that can selectively fail at the end of their lifespan.

[0013] Programmable bonds (PLs) are defined as chemical motifs with specific formation / breakage conditions. Due to their efficiency and ease of use, they have become increasingly popular methods for materials preparation. PLs impart thermally responsive properties. Diels-Alder chemistry is a specific type of PL that has been extensively studied, and the chemical reaction mechanism is well understood. In the Diels-Alder reaction, the dienophile and diene undergo [4+2] cycloaddition to form a six-membered ring. The electronic configurations of the diene and dienophile determine the thermodynamic parameters of ring formation and breakage. For temperature-induced reverse Diels-Alder reactions, the diene is typically electron-rich, while the dienophile is electron-poor.

[0014] The furan / maleimide Diels-Alder system is an example of adduct formation occurring at temperatures ranging from room temperature (RT) to 90°C; however, because this is an equilibrium reaction, cyclization reversal begins at 60°C and becomes the dominant reaction at 90°C. The anthracene / maleimide system is another example of the Diels-Alder system, showing adduct formation beginning at 90°C, with the reverse reaction becoming the dominant reaction at approximately 120°C. Furan or anthracene reacts with alkenes to form adducts, and there is no significant overlap between adduct formation and cyclization reversal. Because these equilibrium reactions overlap, Diels-Alder exchange can occur, where the dissociated adduct can recombine with other components present in the system to form new combinations. For example, furan / maleimide adducts can exchange for anthracene / maleimide adducts.

[0015] The development of failable (detachable) adhesives began with the incorporation of Diels-Alder programmable bonds (PLs) into adhesive polymer systems. For the purposes of this specification and claims, the terms "failable" and "detachable" are used interchangeably herein. PLs can be incorporated into a range of different polymers, providing the ability to tune failable adhesives for a range of physical properties. In most adhesive formulations, the type of base polymer determines many properties, such as mechanical strength, substrate compatibility, curing time, elastic recovery, creep properties, and other properties known to those skilled in the art. Therefore, it is important to have systems that can be widely applied to many existing adhesive systems. Thermosetting adhesive systems, such as… Figure 1 As shown. Figure 1 One example is the use of polyurethane, where the macrospheres represent polyol crosslinking agents and the microspheres represent difunctional isocyanates. Alternatively, the reactive groups can be reversed. Different polyurethane systems can use macrospheres as polyfunctional isocyanates (more than two reactive groups) and microspheres as polymers, oligomers, or small-molecule diols. Epoxy systems are also possible. Figure 1Examples of this system use large spheres as multifunctional epoxy groups and small spheres as bifunctional reactive groups compatible with epoxy (this can include amines, multifunctional acids, thiols, phenols, acid anhydrides, and alcohols, etc.). The system can also be reversed, with large spheres representing multifunctional polymers, oligomers, or small molecules containing functional groups that react with epoxy groups (as described above), and small spheres representing bifunctional epoxy polymers, oligomers, or small molecules. Another example is a silane system, which can include multifunctional siloxane materials having more than one terminal functional group (large spheres) that reacts with bifunctional polymers, oligomers, or small molecules (small spheres). The reverse is also true. Each of these systems can be combined with another, as modified siloxanes containing functional groups such as polyurethanes, epoxy resins, and acrylic resins already exist.

[0016] In this paper, the inventors have specifically designed and formulated a balance of reversible Diels-Alder bonds and irreversible bonds, incorporating them into a polymer matrix to produce an adhesive that is durable throughout the product's lifespan but weakens or fails upon exposure to stimuli. In this case, the stimuli are heat. By creating formulations specifically targeting the available reversible and irreversible reactions, both adhesion and cracking properties can be tailored.

[0017] Regardless of the base adhesive system material used for mechanical and compatibility reasons, thermal programmability is influenced by the balance between reversible and irreversible crosslinking. Formulations can be customized based on the Diels-Alder system and the concentration of the diephile used. By combining these different Diels-Alder systems, the exchange of bonds is programmable, which determines the balance between reversible and irreversible crosslinking. Figure 2 This diagram illustrates the interconversion of Diels-Alder adducts in a releaseable adhesive formulation as temperature and curing state increase. It shows the crosslinking that can occur when using Diels-Alder programmable linkers in adhesive formulations. The large spheres represent multifunctional polymers, and the small circles demonstrate how programmable bonds can dissociate and exchange within the temperature range in which cyclization reversal is induced. Most of the processing and application of the adhesive occurs in stage B, where the chains are still fluid. Once the temperature reaches the “bonding” or curing range of stage C, some reversible crosslinking has dissociated. At this point, while the recently dissociated diene and dienophile may recombine, the presence of a diene scavenger creates opportunities for the binding of the diene and the scavenger, resulting in adducts at higher temperatures. These higher-temperature adducts will form part of the formulation in the bonding stage but can be reactivated (i.e., dissociated) by heating the system to even higher temperatures (outside the normal ambient conditions observed in adhesives). Once at this higher temperature, diene-dienephile and diene-diene trap adduct dissociate, the network is restructured, and the adhesive and cohesive forces that hold the adhesive and substrate together are reduced. Figure 1This is a diagram illustrating the forward and reverse Diels-Alder reactions of each diene-dienophile and diene-dien trap adduct. The overlay diagram represents the temperature ranges in which the adhesive processing, bonding, and debonding steps occur.

[0018] On one hand, the present invention relates to bonding two substrates together using a removable adhesive. The substrates may include synthetic or natural fibers, blends of synthetic or natural fibers, textiles based on synthetic or natural fibers, textiles containing synthetic or natural fibers, plastic films and sheets, molded plastic parts, paper, ceramics, glass, metals, or any combination thereof.

[0019] The formulation requires a programmable bond consisting of a Diels-Alder adduct, which is selected as a combination of a diene and a dienophile. The diene can be selected from modified furans, modified furans, modified anthracenes, modified conjugated alkenes (e.g., butadiene and its derivatives), and modified conjugated imines (referred to as azido-Diels-Alder reactions). The dienophile functional group can be selected from modified maleimides, modified alkenes, modified alkynes, modified imides (referred to as imide-Diels-Alder reactions), modified aldehydes (referred to as oxo-Diels-Alder reactions), or modified ketones.

[0020] These programmable bonds can be installed in situ or ex-situ on multifunctional polymers (typically oligomeric or polymeric polyols with a functionality of 2.0 or higher) to form a network. Such materials can include a variety of polymer classes selected based on their adhesive properties. For example, these polymer classes include, but are not limited to, polyolefins (including polyethylene, polypropylene, poly-1-hexene, polymethylpentene), polyesters (including PET, PBAT, PBT, and their variants), polyethers (including polyoxomethlyene, polyethylene glycol, polyethylene oxide, polypropylene oxide, polybutane oxide, and polyphenylene ether), polystyrene, polyhydroxyalkanoates, polyisoprene, polybutadiene, polysiloxanes, polyimides, polyethersulfone, polyetheretherketone, liquid crystal polymers, polyamides, polycarbonates, polyacrylates, and polyurethanes. Other polyols that can be used include naturally derived polyols, such as carbohydrate-based materials including starch, monosaccharides, and polysaccharides, and derivatives of natural oils, including soybean oil, rapeseed oil, castor oil, peanut oil, and sunflower oil.

[0021] To achieve the desired failability and cracking properties, the full adhesive formulation must include an additional diene scavenger. A diene scavenger is defined herein as a dienophile that reacts with and scavenges free diene released via a reverse Diels-Alder reaction, or is intentionally included in the adhesive formulation for the desired properties. This mechanism provides the network's splittability, which allows the desired adhesive failure to occur upon application of heat. Furthermore, preferred diene scavengers are selected from the preceding list of dienophiles, such that the adduct consisting of the available free diene and the diene scavenger does not undergo a reverse Diels-Alder reaction at the temperature required for detackability. In the examples provided below, the diene scavenger is a residual olefin present on polybutadiene, both on diene-dieneophile-modified polybutadiene and on base hydroxyl-terminated polybutadiene. In other embodiments, the diene scavenger may be an additional small molecule, oligomer, or polymer that is specifically added to modulate properties including tackiness, flowability, mechanical strength, bonding temperature, detack temperature, and application or processing performance. Furthermore, these diene scavengers can be added to formulations as small molecule additives, or they can be attached to polymers in the formulation. These scavengers do not need to be identical and can be included as a mixture of different types of diene scavengers to further modify the debinding properties.

[0022] As those skilled in the art will recognize, the adhesive formulations of this disclosure may include additional additives that do not specifically interact with the component diene, dienophile, or diene scavenger to enhance additional properties that improve processing, adhesion, flow, or aesthetic performance. As a non-exhaustive list, some of these additives may include waxes, tackifiers, UV stabilizers, acid scavengers, free radical scavengers, fillers, pigments, dyes, antistatic agents, etc.

[0023] In this document, the dienophile is referred to as A, the diene as B, and the diene scavenger as AT. In some embodiments, the molar ratio of the dienophile to the diene, defined as A:B, has an excess of diene, for example, a molar ratio of 0.10-0.75, 0.10-0.50, or 0.15-0.30. In some embodiments, the molar ratio of the diene scavenger to the diene, defined as AT:B, has an excess of diene scavenger, and the molar ratio is 1-25 or 5-15.

[0024] Because polymer networks can be assembled in a variety of ways, maintaining a suitable ratio of programmable to non-programmable bonds is important. In the examples below, programmable bonds (PL) are Diels-Alder adducts (specifically, maleimide-furan, maleimide-fulren, and maleimide-anthracene), while non-programmable bonds (N) are additional isocyanate functional groups that provide network connectivity but cannot be thermally dissociated. For debinding systems, the PL:N ratio can be 0.01–4, 0.1–1, or 0.5–0.9. While the examples described below demonstrate this concept using non-programmable isocyanate linkers, it can be similarly implemented with other reaction systems, such as epoxides, silanes (including acetoxy, oxime, and alkoxy), metals, carbodiimides, etc.

[0025] In the embodiments provided below, the adhesive formulation is a solution that can be coated onto a substrate, such as a release liner, and treated as a hot-melt adhesive film. In some embodiments, the adhesive formulation is referred to as a "Phase B" thermosetting material. The temperature range for bonding the Phase B thermosetting material of the present invention depends on the application, and the debonding step can be performed at a temperature higher than the application temperature.

[0026] In one embodiment of the invention, a detackable adhesive formulation is provided, comprising (i) a multifunctional polymer having programmable bonds formed from Diels-Alder adducts, and (ii) a concentration of a diene scavenger. The programmable bonds comprise one or more diene-diene pairs capable of forming Diels-Alder adducts. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, which remains stable until dissociation at the detackable temperature of the adhesive. In the detackable adhesive formulation, the molar number of the diene scavenger exceeds the molar number of one or more dienes. The detackable adhesive formulation can be applied as a coating or extruded. The adhesive temperature of the detackable adhesive formulation is from 30°C to 150°C, and the detackable temperature is 130°C or higher. When the detackable adhesive formulation is at or above the detackable temperature, at least a portion of one or both of the programmable bonds and the diene-diene scavenging adduct dissociates, and the adhesive strength decreases. Adhesive formulations include nonprogrammable bonds that do not dissociate at failure temperatures.

[0027] In another embodiment of the invention, a method for forming a detackable adhesive is provided, the method comprising forming a multifunctional crosslinkable polymer comprising a diene, a dienophile, and a diene trapping agent at a certain concentration. In this method, the diene and the dienophile react to form a first Diels-Alder adduct. The diene trapping agent is (i) a potential olefin or (ii) a functional group selected from those that will react with the diene to form a diene-diene trapping adduct, which remains stable until dissociation at the detackable temperature of the adhesive. The molar number of the diene trapping agent exceeds the molar number of the diene. At the adhesive bonding temperature of the adhesive, the presence of the diene-diene trapping adduct is dominant. At the detackable temperature of the adhesive, the reverse Diels-Alder reaction of the first and second Diels-Alder adducts is dominant, and the adhesive strength of the adhesive decreases. The adhesive bonding temperature is from 30°C to 150°C. The detackable temperature is a temperature equal to or higher than 150°C, and the multifunctional crosslinkable polymer comprises bonds that do not dissociate at the detackable temperature.

[0028] Furthermore, the removable adhesive material of the present invention can be prepared in other forms. One such form is referred to in the art as a "2K" formulation. Examples of such formulations include two-component polyurethanes, in which the reactive portions (e.g., polyols and isocyanates) remain separate until ready for use. Other examples include two-component epoxy-based and two-component silyl or siloxane-based removable adhesives. When the two components of the removable adhesive are ready for use, they are mixed, and a crosslinking reaction begins. The adhesive material can then be added to the substrate in a liquid manner, either manually or via an automated assembly line. The two components do not necessarily have to be liquid in nature, as there are systems with two components that arrive in the form of two liquids, two soft solids, or a liquid and a solid. The two-component removable adhesive can be applied as a coating or paint, or administered using a syringe or other applicator.

[0029] In one aspect, a two-component adhesive formulation is provided, comprising (i) a first formulation comprising a first polyol crosslinker having two or more reactive alcohol functional groups and a programmable bond comprising a Diels-Alder adduct, and (ii) a second formulation comprising the first polyol crosslinker, another polyol crosslinker capable of reacting with the first polyol functional groups, or a diisocyanate, wherein one or both of the first and second formulations comprise a diene scavenger at a certain concentration. The programmable bond comprises one or more diene-diene pairs capable of forming a Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, the adduct remaining stable until dissociated at a debonding temperature. The molar number of the diene scavenger exceeds the molar number of one or more dienes. After mixing the first and second formulations, the adhesive formulation has a bonding temperature of 30°C to 150°C. The mixed adhesive formulation has a detack temperature above 130°C. When the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene capture adduct dissociates, resulting in a decrease in adhesive strength. The mixed adhesive formulation includes non-programmable bonds that do not dissociate at the detack temperature. In another embodiment of the formulation, Diels-Alder bonds may be incorporated into the diisocyanate instead of the polyol crosslinker. For example, a first formulation may replace an isocyanate comprising two or more reactive functional groups and a first polyol crosslinker comprising two or more reactive alcohol functional groups, the isocyanate having programmable bonds formed by the Diels-Alder adduct; and (ii) a second formulation may replace a polyol crosslinker comprising two or more reactive alcohol functional groups, which need not include Diels-Alder bonds.

[0030] In another aspect, a two-component adhesive formulation is provided, comprising: (i) a first formulation comprising an epoxy crosslinker having two or more reactive functional groups and a programmable bond having a combination formed from a Diels-Alder adduct; and (ii) a second formulation comprising a polyol or polyamine having two or more reactive functional groups capable of reacting with the epoxy crosslinker. One or both of the first and second formulations contain a diene scavenger at a certain concentration. The programmable bond comprises one or more diene-dienophile pairs capable of forming a Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, which remains stable until dissociated at a debonding temperature. The molar number of the diene scavenger exceeds the molar number of one or more dienes. After mixing the first and second formulations, the adhesive formulation has a bonding temperature of 30°C to 150°C. The mixed adhesive formulation has a detack temperature above 130°C. When the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene capture adduct dissociates, resulting in a decrease in adhesive strength. The mixed adhesive formulation includes non-programmable bonds that do not dissociate at the detack temperature. In another embodiment of the formulation, Diels-Alder bonds may be incorporated into a polyol or polyamine crosslinker instead of an epoxy crosslinker. For example, a first formulation comprises a polyol or polyamine crosslinker having two or more reactive functional groups and a programmable bond formed by a Diels-Alder adduct; and (ii) a second formulation comprises an epoxy crosslinker having two or more reactive functional groups capable of reacting with the polyol or polyamine crosslinker.

[0031] In another embodiment, a two-component adhesive formulation is provided, comprising: (i) a first formulation comprising a silane crosslinking agent having two or more reactive functional groups and a programmable bond having a combination formed from a Diels-Alder adduct; and (ii) a second formulation comprising a silane or siloxane having two or more reactive functional groups capable of reacting with the silane crosslinking agent. One or both of the first and second formulations comprise a diene scavenger at a certain concentration. The programmable bond comprises one or more diene-dienophile pairs capable of forming a Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, which remains stable until dissociated at a debonding temperature. The molar number of the diene scavenger exceeds the molar number of one or more dienes. After mixing the first and second formulations, the adhesive formulation has a bonding temperature of 30°C to 150°C. The mixed adhesive formulation has a detack temperature above 130°C. When the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene trap adduct dissociates, resulting in a decrease in adhesive strength. The mixed adhesive formulation includes non-programmable bonds that do not dissociate at the detack temperature.

[0032] One-component systems (also known as moisture-curing or "1K") can also be used as the base reaction system to bind adhesive materials. Siloxane adhesives and sealants are frequently used as 1K moisture-curing systems, but other systems, including polyurethanes, are also used. By incorporating PL into one of these formulations, removable sealants and encapsulants for industrial applications such as construction, aerospace, and electronics can be produced. In fact, vinyl-containing silanes are commonly used to improve filler compatibility, bond strength, and the performance of other formulations, and, according to the methods described herein, can function well as diene-capturing systems.

[0033] In the methods and adhesive formulations described herein, one or more diene-dienophile pairs may be selected from furan-maleimide, anthracene-maleimide, and furene-maleimide, and combinations thereof.

[0034] In one embodiment, one or more diene-diene pairs of the releaseable adhesive formulation provided herein comprise furan-maleimide, with an adhesive temperature of 65-100°C and a release temperature of 110-160°C.

[0035] In another embodiment, one or more diene-diene pairs of the detackable adhesive formulation provided herein include fulvin-maleimide, with an adhesive temperature of 75-110°C and a detack temperature of 120-160°C.

[0036] In yet another embodiment, one or more diene-diene pairs of the detackable adhesive formulation provided herein include anthracene-maleimide, with an adhesive temperature of 90-130°C and a detack temperature of 130-160°C.

[0037] The adhesive material of the present invention can also be prepared in the form of glue sticks. These glue sticks can be prepared from a solvent by solution casting, or as a pure molten material heated to a temperature at which the polymer system can operate, but not yet fully cured and shaped by extrusion, injection molding, or casting.

[0038] With proper formulation, adhesive systems can also be cured by radiation-based curing (UV, electron beam, infrared, microwave, X-ray or gamma radiation).

[0039] In each adhesive system described herein, the combination of a programmable linker (PL) and a diene trapping agent (DT) is a key aspect of the invention. Without being bound by theory, the PL and DT systems can be incorporated into a wide variety of basic one-component or two-component polymer systems currently used for crosslinking systems. Examples are well known to those skilled in the art and include, but are not limited to, polyurethanes, polyureas, epoxy resins, silicone resins, oximes, acrylics, acrylic copolymers, modified olefins, rubbers (synthetic and natural), or polysulfides.

[0040] The present invention will now be described in more detail by way of embodiments, but these embodiments are not intended to limit the present invention.

[0041] Example The formulations used in these examples are described below. The same polymer base was used in all these experiments: hydroxyl-terminated polybutadiene (HTPB). This multifunctional polymer can be replaced by different polyols with side chains or bound diene scavengers. Alternatively, the diene scavenger can be a small molecule additive in the matrix. Each of these prototype formulations uses a different diene (furan, furan, and anthracene) as the counterpart to the maleimide dienophile. By using different Diels-Alder pairs, differences in the system's heat resistance and final debinding temperature can be obtained.

[0042] Example 1 Bicomponent B-stage thin film (furan as diene) - Experiment: Add a diisocyanate (2.4 equivalents (eq)), such as 1,6-hexamethylene diisocyanate (HMDI), diphenylmethylene diisocyanate (MDI), isophorone diisocyanate (IPDI), or a combination thereof, to a magnetically stirred rod and cool for 10 minutes. Simultaneously, dissolve N-(4-hydroxyphenyl)maleimide (2 equivalents) in THF in another vial along with dibutyltin dilaurate (0.019 equivalents) as a catalyst. Add the THF solution to a round-bottom flask and remove it from ice. Add the HTPB prepolymer (1 equivalent) to the flask and stir overnight at 50°C. The reaction progress the following day was measured by 1H NMR: (ppm) in The structure was confirmed by novel peaks at 7.10, 6.85, and 6.8 ppm. After confirmation of incorporation into the polymer, furfuryl alcohol (2 equivalents) was added to a flask and heated overnight at 50°C. Samples were taken to confirm the formation of the DA adduct by 1H NMR. The solvent was removed by rotary evaporation, and the resulting weight percentages were calculated. Additional diisocyanate (9.6 equivalents) was mixed into the polymer and partially cured before drawdown with an RDS #50 stick to create a partially cross-linked (B-stage) film on the release liner.

[0043] Example 2 Bicomponent B-stage thin films (enriched as dienes) - Experiment: Add a diisocyanate (2.4 equivalents), such as 1,6-hexamethylene diisocyanate (HMDI), diphenylmethylene diisocyanate (MDI), isophorone diisocyanate (IPDI), or a combination thereof, to a magnetic stir bar and cool for 10 minutes. Simultaneously, dissolve N-(4-hydroxyphenyl)maleimide (2 equivalents) in THF in another vial along with dibutyltin dilaurate (0.019 equivalents) as a catalyst. Add the THF solution to a round-bottom flask and remove it from ice. Add the HTPB prepolymer (1 equivalent) to the flask and stir overnight at 50°C. The reaction progress the following day was measured by 1H NMR: (ppm) in The structure was confirmed by new peaks at 7.10, 6.85, and 6.8 ppm. After confirming the binding to the polymer, butanol-rich olefin (2 equivalents) was added to the flask and heated overnight at 100–130 °C. Additional diisocyanate (9.6 equivalents) was mixed into the polymer and partially cured before being coated with an RDS #50 bar to create a partially cross-linked (B-stage) film on the release liner.

[0044] Example 3 Two-component B-stage thin films (anthracene as diene) - Experiment: Add a diisocyanate (2.4 equivalents), such as 1,6-hexamethylene diisocyanate (HMDI), diphenylmethylene diisocyanate (MDI), isophorone diisocyanate (IPDI), or a combination thereof, to a magnetic stir bar and cool for 10 minutes. Simultaneously, dissolve N-(4-hydroxyphenyl)maleimide (2 equivalents) in THF in another vial along with dibutyltin dilaurate (0.019 equivalents) as a catalyst. Add the THF solution to a round-bottom flask and remove it from ice. Add the HTPB prepolymer (1 equivalent) to the flask and stir overnight at 50°C. The reaction progress the following day was measured by 1H NMR: (ppm) in The structure was confirmed by new peaks at 7.10, 6.85, and 6.8 ppm. After confirming the binding to the polymer, 9-methylene anthracene (2 equivalents) was added to a flask and heated overnight at 100–130 °C. Additional diisocyanate (9.6 equivalents) was mixed into the polymer and partially cured before being coated with an RDS #50 bar to create a partially cross-linked (B-stage) film on the release liner.

[0045] Example 4 General procedure for formulation 'A': Add a diisocyanate, such as 1,6-hexamethylene diisocyanate (HMDI), diphenylmethylene diisocyanate (MDI), isophorone diisocyanate (IPDI), or a combination thereof, along with a magnetic stir bar to a 100 mL round-bottom flask and cool over ice and brine for 10 minutes. In a separate container, mix a diene (butanol-rich or 9-methyleneanthracene) (diene-OH) and one drop of dibutyltin dilaurate (DBTDL) and add it dropwise to the reaction vessel with stirring. Then remove the reaction vessel from the ice and brine and stir at room temperature for 1 hour, adding a small amount of tetrahydrofuran (THF) to keep the reagents dissolved. For each gram of hydroxyl-terminated polybutadiene (HTPB) added, the total amount of THF added in the entire reaction should not exceed 1 mL of THF. Then add HTPB and additional THF. Once the contents are homogeneously mixed, add diene-OH a second time. Then stir the mixture for 2 hours. At this point, add N-(4-hydroxyphenyl)maleimide (PM) and stir until the mixture is visually homogeneous. Once complete, cover the container with a rubber diaphragm, secure it with copper wire, and place it in an oil bath with stirring overnight (temperature settings - 60-90°C for butanol-rich olefins; 100-130°C for 9-methyleneanthracene).

[0046] Example 5 General procedure for formulation 'A2': Add a diisocyanate, such as 1,6-hexamethylene diisocyanate (HMDI), diphenylmethylene diisocyanate (MDI), isophorone diisocyanate (IPDI), or a combination thereof, along with a magnetic stir bar to a 100 mL round-bottom flask and cool it over ice and brine for 10 minutes. In a separate container, mix and add dropwise a diene (butanol-rich or 9-methyleneanthracene) (diene-OH), one drop of DBTDL, and THF (20 vol% diene-OH) to the reaction vessel. Remove the reaction vessel from the ice and brine and stir at room temperature for 1 hour. Then add a solution of HTPB and THF (1 mL THF per gram of HTPB). Once the contents are homogeneous, add the diene-OH a second time and stir at room temperature for 2 hours. At this point, add N-(4-hydroxyphenyl)maleimide (PM) and stir into the reaction until the mixture is visually homogeneous. Then cover the container with a rubber diaphragm, secure it with copper wire, and stir it overnight in an oil bath (temperature settings - 60-90°C for butanol-rich olefins; 100-130°C for 9-methanol-anthracene).

[0047] Example 6 General procedure for formulation 'A3': Add a diisocyanate, such as 1,6-hexamethylene diisocyanate (HMDI), diphenylmethylene diisocyanate (MDI), isophorone diisocyanate (IPDI), or a combination thereof, to a 100 mL round-bottom flask, along with a magnetic stir bar, and cool over ice and brine for 10 minutes. In a separate container, mix a diene (butanol-rich or 9-methyleneanthracene) (diene-OH) and one drop of DBTDL and add it dropwise to the reaction vessel. Then remove the reaction vessel from the ice and brine and stir at room temperature for 1 hour. Next, add a solution of HTPB and THF (1 mL THF per gram of HTPB). Once the contents are well mixed, add the diene-OH a second time and stir at room temperature for 2 hours. At this point, add N-(4-hydroxyphenyl)maleimide (PM) and stir into the reaction until it is visually homogeneous. Then cover the container with a rubber diaphragm, secure it with copper wire, and stir it overnight in an oil bath (temperature settings - 60-90°C for butanol-rich olefins; 100-130°C for 9-methanol-anthracene).

[0048] Example 7 General procedure for formulation 'A4': Add a diisocyanate, such as 1,6-hexamethylene diisocyanate (HMDI), diphenylmethylene diisocyanate (MDI), isophorone diisocyanate (IPDI), or a combination thereof, to a 100 mL round-bottom flask, along with a magnetic stir bar, and cool over ice and brine for 10 minutes. In a separate container, mix a diene (butanol-rich or 9-methyleneanthracene) (diene-OH) and one drop of DBTDL and add it dropwise to the reaction vessel. Then remove the reaction vessel from the ice and brine and stir at room temperature for 1 hour. Then add a solution of HTPB and THF (1 mL THF per gram of HTPB). Once the contents are homogeneous, add N-(4-hydroxyphenyl)maleimide (PM) and stir until homogeneous by visual inspection. Then cover the vessel with a rubber diaphragm, secure it with copper wire, and stir overnight in an oil bath (temperature settings - 60-90°C for butanol-rich; 100-130°C for 9-methyleneanthracene).

[0049] Example 8 Adhesion test of the adhesive formulation that may fail General procedures for testing formulations The formulation was cut into 4-inch x 4-inch samples and applied to 4-inch x 6-inch 100% polyester knitted fabric. The adhesive sample was then bonded to the fabric using a manual hot press by heating and pressurizing (typically 65°C for 30 seconds). The release liner was then removed from the laminate, leaving the exposed adhesive, and another layer of fabric was applied to the stack. The structure was then bonded under various combinations of time, temperature, and pressure to produce a fully bonded laminate.

[0050] These laminated structures were cut into 1-inch strips, and peel strength was assessed using the t-peel method on a general tensile testing machine. Samples with peel strength greater than 100 N / m were then subjected to high temperatures (>130°C) to determine debonding properties. Successful samples were too weak to be measured using our equipment.

[0051] Those skilled in the art will readily understand that this disclosure is highly suitable for achieving these objectives and obtaining the mentioned objectives and advantages, as well as those inherent therein. This disclosure is representative of embodiments that are exemplary and are not intended to limit the scope of this disclosure. Variations and other uses will occur to those skilled in the art within the spirit of this disclosure as defined by the claims.

[0052] No reference, including any non-patent or patent literature cited in this specification, is acknowledged as prior art. It should be understood that, unless otherwise stated, reference to any literature herein does not constitute an admission that any of such literature constitutes part of common general knowledge in the art in the U.S. or any other country. Any discussion of the references represents the claims of their authors, and the applicant reserves the right to challenge the accuracy and relevance of any reference cited herein. Unless otherwise expressly stated, all references cited herein are incorporated herein by reference. In the event of any discrepancies between any definitions and / or descriptions found in the cited references, this disclosure shall prevail.

Claims

1. A detackible adhesive formulation, comprising: (i) A multifunctional polymer having programmable bonds made of Diels-Alder adducts, and (ii) A diene scavenger of a certain concentration, wherein: The programmable bond comprises one or more diene-dienophile pairs capable of forming the Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, the adduct remaining stable until dissociation at the debonding temperature of the adhesive, wherein the molar number of the diene scavenger exceeds the molar number of the one or more dienes. The detackable adhesive formulation can be used as a coating. The detackable adhesive formulation can be extruded. The adhesive formulation has a bonding temperature of 30°C to 150°C. The adhesive formulation has a detack temperature of 130°C or higher, wherein when the detack-free adhesive formulation is at or above the detack temperature, at least a portion of one or both of the programmable bond and the diene-diene trap adduct dissociates, resulting in a decrease in adhesive strength. The adhesive formulation includes non-programmable bonds that do not dissociate at the debonding temperature.

2. The removable adhesive formulation according to any one of claims 1, 23, 24, 26-28, wherein the one or more diene-dienophile pairs are selected from furan-maleimide, anthracene-maleimide, and furene-maleimide, and combinations thereof.

3. The removable adhesive formulation according to claim 1 or claim 2, wherein the one or more diene-diene pairs comprise furan-maleimide, the bonding temperature is 65-100°C, and the removable temperature is 110-160°C.

4. The removable adhesive formulation according to claim 1 or claim 2, wherein the one or more diene-diene pairs comprise fulvin-maleimide, the bonding temperature is 75-110°C, and the removable temperature is 120-160°C.

5. The removable adhesive formulation according to claim 1 or claim 2, wherein the one or more diene-diene pairs comprise anthracene-maleimide, the bonding temperature is 90-130°C, and the removable temperature is 130-160°C.

6. The desiccant adhesive formulation according to any one of the preceding claims, wherein the multifunctional polymer contains 2.0 or greater functionality for network forming capability.

7. The detackable adhesive formulation according to any one of the preceding claims, wherein the multifunctional polymer comprises oligomeric polyols or polymeric polyols.

8. The removable adhesive formulation according to any one of the preceding claims, wherein the multifunctional polymer comprises polyolefins (including polyethylene, polypropylene, poly-1-hexene, polymethylpentene), polyesters (including PET, PBAT, PBT and variants thereof), polyethers (including polyoxymethylene, polyethylene glycol, polyethylene oxide, polypropylene oxide, polybutane and polyphenylene ether), polystyrene, polyhydroxyalkanoates, polyisoprene, polybutadiene, polysiloxane, polyimide, polyethersulfone, polyetheretherketone, liquid crystal polymers, polyamides, polycarbonates, polyacrylates, polyurethanes, carbohydrate-based polyols, starch, monosaccharides and polysaccharides, derivatives of natural oils including soybean oil, rapeseed oil, castor oil, peanut oil, or sunflower oil, and combinations thereof.

9. The removable adhesive formulation according to any one of the preceding claims, wherein the multifunctional polymer comprises a thermosetting polymer or a thermoplastic polymer.

10. An adhesive film, said adhesive film being produced by coating from a removable adhesive formulation according to any one of the preceding claims.

11. An adhesive film, said adhesive film being produced by extrusion of any one of claims 1-9 of a removable adhesive formulation.

12. A textile laminate made using any one of claims 1-9.

13. A plastic laminate made using any one of claims 1-9.

14. A composite structure made using any one of claims 1-9 of a removable adhesive formulation, the composite structure comprising synthetic or natural fibers, blends of synthetic or natural fibers, textiles based on synthetic or natural fibers, textiles containing synthetic or natural fibers, plastic films or sheets, molded plastic parts, paper, ceramics, glass, or metals, or any combination thereof.

15. The removable adhesive formulation according to any one of the preceding claims, comprising one or more additives to improve flowability, adhesion or other properties.

16. The desiccant adhesive formulation according to any one of the preceding claims, wherein the molar ratio of the dienophile to the diene is 0.10-0.

75.

17. The desiccant adhesive formulation according to any one of the preceding claims, wherein the molar ratio of the dienophile to the diene is 0.10-0.

50.

18. The desiccant adhesive formulation according to any one of the preceding claims, wherein the molar ratio of the dienophile to the diene is 0.15-0.

30.

19. The desiccant adhesive formulation according to any one of the preceding claims, wherein the molar ratio of the diene scavenger to the diene is greater than 1 to 25.

20. The desiccant adhesive formulation according to any one of the preceding claims, wherein the molar ratio of the diene scavenger to the diene is 5 to 15.

21. The desiccant adhesive formulation according to any one of the preceding claims, wherein the molar ratio of the programmable bond to the non-programmable bond is 0.01-4, 0.1-1, or 0.5-0.

9.

22. The removable adhesive formulation according to any one of the preceding claims, wherein the removable adhesive formulation is a stage B thermosetting adhesive.

23. A two-component adhesive formulation, comprising: (i) A first formulation comprising a first polyol crosslinking agent having two or more reactive alcohol functional groups, and a programmable bond comprising a combination made of a Diels-Alder adduct, and (ii) A second formulation comprising the first polyol crosslinking agent, another polyol crosslinking agent capable of reacting with the functional group of the first polyol, or a diisocyanate, wherein one or both of the first and second formulations comprise a certain concentration of a diene scavenger, wherein: The programmable bond comprises one or more diene-dienophile pairs capable of forming the Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, the adduct remaining stable until dissociation at a debinding temperature, wherein the molar number of the diene scavenger exceeds the molar number of the one or more dienes. After the first and second formulations are mixed, the bonding temperature of the mixed adhesive formulation is 30°C to 150°C. The mixed adhesive formulation has a debonding temperature above 130°C, wherein when the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene trap adduct dissociates, the adhesive strength decreases, and... The mixed adhesive formulation includes non-programmable bonds that do not dissociate at the debonding temperature.

24. A two-component adhesive formulation, comprising: (i) a first formulation comprising an isocyanate having two or more reactive functional groups and a first polyol crosslinking agent having two or more reactive alcohol functional groups, said isocyanate being bonded with programmable bonds made of Diels-Alder adducts; and (ii) A second formulation comprising the first polyol crosslinking agent or another polyol crosslinking agent having two or more reactive alcohol functional groups, wherein one or both of the first and second formulations comprise a certain concentration of a diene scavenger, wherein: The programmable bond comprises one or more diene-dienophile pairs capable of forming a Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, the adduct remaining stable until dissociation at a debinding temperature, wherein the molar number of the diene scavenger exceeds the molar number of the one or more dienes. After the first and second formulations are mixed, the bonding temperature of the mixed adhesive formulation is between 30°C and 150°C. The mixed adhesive formulation has a debonding temperature above 130°C, wherein when the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene trap adduct dissociates, the adhesive strength decreases, and... The mixed adhesive formulation includes non-programmable bonds that do not separate at a debonding temperature.

25. The two-component adhesive formulation according to claim 23 or 24, wherein the two-component adhesive formulation is a polyurethane adhesive formulation.

26. A two-component adhesive formulation, comprising: (i) A first formulation comprising an epoxy crosslinking agent having two or more reactive functional groups, and a programmable bond having a combination made of Diels-Alder adduct; as well as (ii) A second formulation comprising a polyol or polyamine having two or more reactive functional groups capable of reacting with the epoxy crosslinking agent, wherein one or both of the first and second formulations comprise a diene scavenger at a certain concentration, wherein: The programmable bond comprises one or more diene-dienophile pairs capable of forming a Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, the adduct remaining stable until dissociation at a debinding temperature, wherein the molar number of the diene scavenger exceeds the molar number of the one or more dienes. After the first and second formulations are mixed, the bonding temperature of the mixed adhesive formulation is between 30°C and 150°C. The mixed adhesive formulation has a debonding temperature above 130°C, wherein when the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene trap adduct dissociates, the adhesive strength decreases, and... The mixed adhesive formulation includes non-programmable bonds that do not separate at a debonding temperature.

27. A two-component adhesive formulation, comprising: (i) a first formulation comprising a polyol or polyamine crosslinking agent having two or more reactive functional groups, and a programmable bond having a combination made of a Diels-Alder adduct; and (ii) A second formulation comprising an epoxy crosslinking agent having two or more reactive functional groups capable of reacting with the polyol or polyamine crosslinking agent, wherein one or both of the first and second formulations comprise a certain concentration of a diene scavenger, wherein: The programmable bond comprises one or more diene-dienophile pairs capable of forming a Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, the adduct remaining stable until dissociation at a debinding temperature, wherein the molar number of the diene scavenger exceeds the molar number of the one or more dienes. After the first and second formulations are mixed, the bonding temperature of the mixed adhesive formulation is between 30°C and 150°C. The mixed adhesive formulation has a debonding temperature above 130°C, wherein when the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene trap adduct dissociates, the adhesive strength decreases, and... The mixed adhesive formulation includes non-programmable bonds that do not separate at a debonding temperature.

28. A two-component adhesive formulation, comprising: (i) a first formulation comprising a silane crosslinking agent having two or more reactive functional groups, and a programmable bond having a combination made of a Diels-Alder adduct; and (ii) A second formulation comprising a silane or siloxane having two or more reactive functional groups capable of reacting with a silane crosslinking agent, wherein one or both of the first and second formulations comprise a diene scavenger at a certain concentration, wherein: The programmable bond comprises one or more diene-dienophile pairs capable of forming a Diels-Alder adduct. The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with one or more dienes to form a diene-diene scavenging adduct, the adduct remaining stable until dissociation at a debinding temperature, wherein the molar number of the diene scavenger exceeds the molar number of the one or more dienes. After the first and second formulations are mixed, the bonding temperature of the mixed adhesive formulation is between 30°C and 150°C. The mixed adhesive formulation has a debonding temperature above 130°C, wherein when the mixed adhesive formulation is at or above 130°C, at least a portion of one or both of the programmable bond and the diene-diene trap adduct dissociates, the adhesive strength decreases, and... The mixed adhesive formulation includes non-programmable bonds that do not separate at a debonding temperature.

29. The two-component adhesive formulation according to any one of claims 23-28, wherein the mixed adhesive can be applied as a coating or as a paint, or applied with a syringe or other applicator.

30. A method for forming a removable adhesive, the method comprising: A multifunctional crosslinkable polymer is formed comprising a certain concentration of diene, dienophile, and diene scavenger, wherein: The diene and dienophile react to form the first Diels-Alder adduct; The diene scavenger is (i) a potential olefin or (ii) a functional group selected from those that react with a diene to form a diene-diene scavenging adduct, the adduct remaining stable until it dissociates at the detack-free temperature of the adhesive; The molar number of the diene scavenger exceeds the molar number of the diene; At the bonding temperature of the adhesive, the presence of the diene-diene trap adduct is dominant; At the detack-free temperature of the adhesive, the reverse Diels-Alder reaction of the first and second Diels-Alder adducts predominates, resulting in a decrease in adhesive strength. The bonding temperature is 30°C to 150°C; The debonding temperature is equal to or higher than 150°C; and The multifunctional crosslinkable polymer includes bonds that do not dissociate at the debonding temperature.

Images