Electrically detachable single-component siloxane-modified thermally conductive polyurethane hot-melt adhesive, preparation method therefor, and use thereof

Abstract

The present invention belongs to polyurethane hot-melt adhesives, and relates to an electrically detachable single-component siloxane-modified thermally conductive polyurethane hot-melt adhesive, a preparation method therefor, and a use thereof. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot-melt adhesive contains a siloxane-modified polyurethane prepolymer and a modified filler composition, and optional a catalyst and a water absorber; the modified filler composition contains a thermally conductive filler, an electrolyte salt, and a silane coupling agent, and optional a polar solvent compound; the electrically detachable single-component siloxane-modified thermally conductive polyurethane hot-melt adhesive exhibits a bonding strength attenuation of more than 80% after being energized at a voltage of 1V to 100V. The single-component silane-modified thermally conductive polyurethane hot-melt adhesive provided by the present invention has the advantages of good thermal conductivity, excellent bonding performance, and being detachable upon energization, and has broad practical application prospects.

Description

A detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive, its preparation method, and its application.

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 2024114606256, filed on October 18, 2024, entitled "An electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive and its preparation method and application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention pertains to polyurethane hot melt adhesives, specifically a detachable, single-component, siloxane-modified, thermally conductive polyurethane hot melt adhesive, its preparation method, and its applications. Background Technology

[0004] With the continuous development and maturation of the electronics industry, the size of internal components in electronic devices is gradually decreasing, and the component density per unit volume is increasing. During operation, the internal ambient temperature rises continuously, causing rapid heat accumulation. Therefore, effective heat dissipation is crucial for the safe operation of the entire system. Thermally conductive structural adhesives are often used in electronic products such as smartphones and tablets. A common thermally conductive structural adhesive is polyurethane hot melt adhesive. Polyurethane hot melt adhesives are mainly composed of isocyanate-terminated oligomers. The isocyanate groups in these oligomers can react with moisture in the air, forming a cross-linked chemical structure after complete curing, thus achieving high adhesive strength. However, the covalent bonds formed by the reaction of isocyanate groups with moisture are irreversible, and the cross-linked structure is difficult to destroy. After complete curing, it is usually difficult to disassemble the adhesive. Separating the bonded materials often requires significant external force, high temperatures, and chemical reagents. Furthermore, the disassembly process may damage the bonded materials, resulting in substantial economic losses.

[0005] In recent years, some technologies have been developed to add electrolyte salts to polyurethane hot melt adhesives, giving them the ability to be disassembled under electrical conditions. However, while existing electrically disassembleable polyurethane hot melt adhesives can achieve a decrease in bond strength under electrical conditions, their low thermal conductivity makes them unsuitable for bonding components that are prone to heat generation and require heat dissipation. If heat is difficult to dissipate, there may be significant safety hazards, failing to meet the bonding requirements for high heat dissipation performance. Since polyurethane hot melt adhesives are mainly composed of polymers, which have poor thermal conductivity, existing thermally conductive polyurethane hot melt adhesives typically rely on adding thermally conductive fillers with excellent thermal conductivity to the adhesive components. The addition of high filler content imparts a certain level of thermal conductivity to the polyurethane hot melt adhesive. However, thermally conductive fillers are usually inorganic non-metallic materials, and inorganic materials have poor compatibility with organic polyurethane materials. Surface modification of the thermally conductive fillers is usually required, and the corresponding adhesive materials also need some modification. Existing technologies utilize silane-terminated isocyanates combined with thermally conductive fillers to prepare silane-modified polyurethane adhesives with thermal conductivity. However, these currently prepared thermally conductive silane-modified polyurethane adhesives still suffer from slow curing speeds, requiring extended curing times to establish high bond strength. This hinders rapid assembly on automated production lines, and disassembly remains difficult after complete curing. Furthermore, existing one-component polyurethane structural adhesives are prone to bubble formation during curing, easily leading to bonding defects and affecting bond strength. In thermally conductive bonding applications, bubbles can also form cavities, impeding heat conduction.

[0006] Therefore, there is an urgent need to develop an adhesive with good thermal conductivity, excellent adhesion, and detachability when electrically conductive to meet the market demand for high-performance, detachable, and thermally conductive adhesives. Summary of the Invention

[0007] One of the objectives of this invention is to provide a single-component silane-modified thermally conductive polyurethane hot melt adhesive with good thermal conductivity, excellent adhesion, and detachability when electrically conductive.

[0008] The second objective of this invention is to provide a method for preparing the above-mentioned single-component silane-modified thermally conductive polyurethane hot melt adhesive.

[0009] The third objective of this invention is to provide the application of the above-mentioned single-component silane-modified thermally conductive polyurethane hot melt adhesive in the bonding of electronic products.

[0010] The electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by this invention contains a siloxane-modified polyurethane prepolymer, a modified filler composition, and optionally a catalyst and a water-absorbing agent. The modified filler composition contains a thermally conductive filler, an electrolyte salt, a silane coupling agent, and optionally a polar solvent compound. The isocyanate group content in the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive is 0.2-0.8%, and the mass ratio of the siloxane-modified polyurethane prepolymer to the modified filler composition is 1:(1.5-7.5). The adhesive strength of the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive decreases by more than 80% after being energized at a voltage of 1-100V.

[0011] The method for preparing the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by the present invention includes mixing a siloxane-modified polyurethane prepolymer and a modified filler composition, along with an optional catalyst and a water absorbent, uniformly to obtain the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive.

[0012] After in-depth and extensive research, the inventors of this invention discovered that the reason why existing one-component polyurethane hot melt adhesives have low bonding strength and poor thermal conductivity is mainly due to the following reasons: Firstly, existing one-component silane-terminated polyurethane adhesives completely end the isocyanate groups by using siloxane groups. Although using siloxanes to end the isocyanate groups helps improve the compatibility between the thermally conductive filler and the polymer adhesive, the moisture curing speed of siloxanes is much lower than that of isocyanates, usually requiring a longer time to fully cure. Furthermore, the bonding strength after siloxane moisture curing is also lower than that after isocyanate moisture curing. Secondly, existing thermally conductive fillers have poor compatibility with electrically disintegratable polyurethane hot melt adhesives. Directly adding thermally conductive fillers to electrically disintegratable polyurethane hot melt adhesives easily creates defects at the interface between the thermally conductive filler and the polyurethane hot melt adhesive, which is not conducive to the formation of an effective thermally conductive network, thus hindering the realization of the thermal conductivity function. On the other hand, the curing principle of existing polyurethane hot melt adhesives is that the residual isocyanate groups in the polyurethane hot melt adhesive react chemically with the moisture in the air. However, the reaction between isocyanate and moisture produces carbon dioxide gas. Sometimes, carbon dioxide gas is difficult to escape when the adhesive layer is thick, and it will form air bubbles in the adhesive system. The formation of air bubbles will block the transfer of heat, thereby affecting the adhesive performance and thermal conductivity of the adhesive.

[0013] This invention innovatively utilizes electrolyte salts, silane coupling agents, and optional polar solvent compounds to pre-treat the surface of thermally conductive fillers to obtain modified filler compositions. This not only increases the compatibility between thermally conductive fillers and polyurethane materials, but also allows the electrolyte salts introduced into the modified filler compositions to provide the possibility of Faraday reactions between anions and cations under energized conditions. Introducing this modified filler composition into adhesive systems can endow adhesives with electrolytic disintegration properties. Furthermore, this invention innovatively uses siloxane-modified polyurethane prepolymer as the main component. On the one hand, the wet curing mechanism of siloxane differs from that of isocyanate. Siloxane does not generate bubbles during curing, significantly reducing bubble formation during adhesive curing and preventing bond strength from being affected by bubble-induced bonding defects. It also avoids heat conduction blockage caused by bubble-formed cavities. Moreover, by controlling the isocyanate group content in the siloxane-modified polyurethane prepolymer within the range of this invention, the low bond strength after siloxane wet curing can be effectively compensated for. In other words, the "bubble effect" avoided by siloxane, combined with the post-curing tackification of specific isocyanate groups, effectively imparts good bond strength to the adhesive. On the other hand, the siloxane-modified polyurethane prepolymer has higher compatibility with thermally conductive fillers, significantly increasing the compatibility between thermally conductive fillers and organic polymer adhesives. This effectively volatilizes the thermal conductivity of the thermally conductive fillers. In other words, the "bubble cavity heat resistance" avoided by siloxane, combined with the compatibilization effect of siloxane, effectively imparts good thermal conductivity to the adhesive. In summary, the single-component silane-modified thermally conductive polyurethane hot melt adhesive provided by this invention has the advantages of good thermal conductivity, excellent adhesion, and disassembly when electrically conductive, and has broad prospects for practical application. Detailed Implementation

[0014] The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by this invention exhibits a bonding strength attenuation rate of over 80% after being energized with a voltage of 1 to 100V. Specifically, it can be 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 99%, 100%, or any value between them. The voltage required for disassembling the electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive is preferably 1 to 100V, specifically 1V, 3V, 5V, 7V, 9V, 10V, 20V, 30V, 40V, 50V, 60V, 70V, 80V, 90V, 100V or any value between them; the required energizing time is preferably 1s to 60min, such as 1s, 2s, 5s, 15s, 30s, 40s, 50s, 1min, 5min, 10min, 15min, 20min, 30min, 40min, 50min, 60min or any value between them. The isocyanate group content in the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive is 0.2% to 0.8%, specifically 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any value between them.

[0015] The electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by this invention contains a siloxane-modified polyurethane prepolymer and a modified filler composition, as well as an optional catalyst and a water-absorbing agent. Based on the total weight of the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive, the total content of the siloxane-modified polyurethane prepolymer and the modified filler composition is preferably 90-99.8%, the content of the catalyst is preferably 0.1-5%, and the content of the water-absorbing agent is preferably 0.1-5%. Specifically, the total content of the siloxane-modified polyurethane prepolymer and the modified filler composition is preferably 90%, 92%, 94%, 96%, 98%, 99%, 99.5%, 99.8%, or any value between them. The content of the catalyst and the water-absorbing agent is preferably each independently 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or any value between them. The preferred mass ratio of the siloxane-modified polyurethane prepolymer to the modified filler composition is 1:(1.5 to 7.5), specifically 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, or any value between them.

[0016] In this invention, the siloxane-modified polyurethane prepolymer can be commercially available or prepared using various existing methods. In a preferred embodiment, the siloxane-modified polyurethane prepolymer is prepared by the following method: S11, a polyol compound and a polyisocyanate compound are optionally subjected to a first addition reaction in the presence of a catalyst to obtain an isocyanate-double-terminated polyurethane prepolymer; S12, the isocyanate-double-terminated polyurethane prepolymer is subjected to a second addition reaction with a monothiol silane compound to obtain the siloxane-modified polyurethane prepolymer.

[0017] In the preparation process of the above-mentioned siloxane-modified polyurethane prepolymer, the preferred molar ratio of hydroxyl groups in the polyol compound, isocyanate groups in the polyisocyanate compound, and mercapto groups in the monothiol siloxane compound is 1:(2-2.5):(0.3-0.9). The siloxane-modified polyurethane prepolymer prepared under these conditions not only has low bubble size and good compatibility with thermally conductive fillers, providing good thermal conductivity, but also has excellent adhesion and fast curing speed. Specifically, based on 1 mol of hydroxyl groups in the polyol compound, the content of isocyanate groups in the polyisocyanate compound is preferably 2.0 to 2.5 mol, such as 2.0 mol, 2.1 mol, 2.2 mol, 2.3 mol, 2.4 mol, 2.5 mol, or any value between them; the content of thiol groups in the monothiol siloxane compound is preferably 0.3 to 0.9 mol, such as 0.3 mol, 0.4 mol, 0.5 mol, 0.6 mol, 0.7 mol, 0.8 mol, 0.9 mol, or any value between them.

[0018] In the preparation of the above-mentioned siloxane-modified polyurethane prepolymer, the polyol compound can be any known polyol compound commonly used in polyurethane manufacturing, such as at least one of polyester polyols, polyether polyols, polycarbonate polyols, and polyalkylene polyols. These polyol compounds can be used alone or in combination of two or more. The number-average molecular weight of the polyol compound is preferably 1000–4000 g / mol, specifically 1000, 1500, 2000, 2500, 3000, 3500, 4000 g / mol or any value between these values.

[0019] The polyester polyol may be a polyester polyol obtained by reacting a polycarboxylic acid with a polyol, or a poly-ε-caprolactone polyol obtained by ring-opening polymerization of ε-caprolactone. Examples of the polycarboxylic acids include at least one selected from terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, decamethyldicarboxylic acid, and dodecamethyldicarboxylic acid. Examples of the polyols include at least one selected from ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, and cyclohexanediol.

[0020] The polyether polyol may be selected from ring-opening polymers of ethylene glycol, propylene glycol, tetrahydrofuran, and 3-methyltetrahydrofuran, or random copolymers or block copolymers of ethylene glycol, propylene glycol, tetrahydrofuran, 3-methyltetrahydrofuran, or their derivatives, or a mixture of at least one of the above, or a bisphenol-type polyoxyethylene modifier. The bisphenol-type polyoxyethylene modifier is a polyether polyol obtained by adding an epoxy alkane to the active hydrogen portion of the bisphenol-type molecular backbone; it may be a random copolymer or a block copolymer. The epoxy alkane may be selected from at least one of ethylene oxide, propylene oxide, butane oxide, and isobutane oxide.

[0021] The polycarbonate polyol may be selected from at least one of the following: polycarbonate 1,6-hexanediol polyol, polycarbonate-1,4-butanediol-1,6-hexanediol diol, polycarbonate-1,5-pentanediol-1,6-hexanediol diol, polycaprolactone hexanediol diol, polycarbonate-1,4-cyclohexanediol-1,6-hexanediol diol, polyethylene carbonate diol, polypropylene carbonate diol, polybutylene carbonate diol, and polyhexanediol diol.

[0022] The polyalkylene polyol may be selected from at least one of polybutadiene polyol, hydrogenated polybutadiene polyol, and hydrogenated polyisoprene polyol.

[0023] In the preparation of the above-mentioned siloxane-modified polyurethane prepolymer, the polyisocyanate compound may be selected from at least one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, hydrogenated phenylenedimethylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-pentane diisocyanate, 1,4-phenylenedimethylene diisocyanate, phenylenedimethylene diisocyanate, tetramethylxylene diisocyanate, norbornene dimethyl isocyanate, lysine diisocyanate, triphenylmethane triisocyanate, triphenyl thiophosphate triphenyl isocyanate, and 1,6,11-undecane triisocyanate.

[0024] In the preparation of the above-mentioned siloxane-modified polyurethane prepolymer, the monothiol siloxane compound may be selected from at least one of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane.

[0025] In the preparation process of the above-mentioned siloxane-modified polyurethane prepolymer, the conditions for the first addition reaction and the second addition reaction each independently include a temperature preferably of 70-90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C or any value between them; and a time preferably of 1-5h, such as 1h, 2h, 3h, 4h, 5h or any value between them.

[0026] In this invention, the modified filler composition contains a thermally conductive filler, an electrolyte salt, a silane coupling agent, and optionally a polar solvent compound. The thermally conductive filler is preferably present in a content of 70-85 parts by weight, such as 70, 72, 75, 78, 80, 82, or 85 parts by weight, or any value between therewith; the electrolyte salt is preferably present in a content of 5-15 parts by weight, such as 5, 8, 10, 12, or 15 parts by weight, or any value between therewith; the silane coupling agent is preferably present in a content of 2-7 parts by weight, such as 2, 3, 4, 5, 6, or 7 parts by weight, or any value between therewith; and the polar solvent compound is present in a content of 0-15 parts by weight, such as 0, 1, 3, 5, 7, 9, 11, 13, or 15 parts by weight, or any value between therewith.

[0027] In this invention, the thermally conductive filler is primarily inorganic. It is modified using an electrolyte salt, a silane coupling agent, and optionally a polar solvent compound. The siloxane in the silane coupling agent can surface-modify the inorganic thermally conductive filler. The siloxane end of the silane coupling agent exhibits good adhesion to the inorganic thermally conductive filler, while the organic functional groups at the other end, such as thiol, epoxy, and isocyanate groups, have good compatibility with the organic polymers in the adhesive. Through coupling, this promotes subsequent mixing with adhesive components and improves compatibility. Pre-modifying the thermally conductive filler before adding it to the adhesive serves two purposes: firstly, it allows for thorough surface modification of the inorganic thermally conductive filler using the silane coupling agent; secondly, it removes residual moisture from the solvent, filler, and electrolyte salt components in the modified filler composition, preventing side reactions caused by moisture during subsequent mixing with the adhesive. That is, the pre-mixing process allows for more thorough mixing and modification of the inorganic thermally conductive filler, and more complete water removal, thereby improving the compatibility between the thermally conductive filler and the adhesive. Furthermore, the polar solvent compound can serve as a dispersion and mixing medium for the thermally conductive filler, silane coupling agent, and electrolyte salt.

[0028] The modified filler composition can be obtained by mixing thermally conductive filler, electrolyte salt, silane coupling agent, and optional polar solvent compound in any manner. In a preferred embodiment, the modified filler composition is prepared by the following method: S21, dehydrating the electrolyte salt, silane coupling agent, and optional polar solvent compound under vacuum stirring at 100-120°C and 100-200 r / min for 1-5 h to obtain a pretreated product; S22, reacting the pretreated product with the thermally conductive filler under vacuum stirring at 100-120°C and 100-200 r / min for 3-6 h to obtain the modified filler composition.

[0029] In the preparation process of the above modified filler composition, in step S21, the temperature of the vacuum stirring dehydration is 100-120℃, such as 100℃, 102℃, 104℃, 106℃, 108℃, 110℃, 112℃, 114℃, 116℃, 118℃, 120℃ or any value between them; the rotation speed is 100-200 r / min, such as 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 r / min or any value between them; and the time is 1-5h, such as 1h, 2h, 3h, 4h, 5h or any value between them.

[0030] In the preparation process of the above modified filler composition, in step S22, the temperature of the vacuum stirring reaction is 100-120℃, such as 100℃, 102℃, 104℃, 106℃, 108℃, 110℃, 112℃, 114℃, 116℃, 118℃, 120℃ or any value between them; the rotation speed is 100-200 r / min, such as 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 r / min or any value between them; and the time is 3-6 h, such as 3 h, 4 h, 5 h, 6 h or any value between them.

[0031] In this invention, the thermally conductive filler may include at least one of the following: alumina, magnesium oxide, zinc oxide, nickel oxide, aluminum nitride, silicon nitride, boron nitride, and silicon carbide. Furthermore, the particle size of the thermally conductive filler is preferably 1 nm to 100 μm, such as 1 nm, 50 nm, 100 nm, 500 nm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or any value between them.

[0032] In this invention, the electrolyte salt can be an alkali metal salt and / or an ionic liquid. The alkali metal salt can be a salt composed of an alkali metal cation and an organic acid anion, an inorganic acid anion, or an organic sulfonamide anion, such as at least one of lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonamide)imide, lithium chloride, lithium sulfate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroantimonyate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonamide)imide, sodium chloride, sodium sulfate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroantimonyate, potassium trifluoromethanesulfonate, potassium bis(trifluoromethanesulfonamide)imide, potassium chloride, potassium sulfate, potassium tetrafluoroborate, potassium hexafluorophosphate, and potassium hexafluoroantimonyate. The ionic liquid is a liquid molten salt at room temperature (25°C) and can be composed of organic cations and anions. Specific examples of the organic cations include, but are not limited to, imidazole cations, pyrrole cations, quaternary ammonium salt cations, quaternary phosphate salt cations, pyrrolidine cations, and piperidine cations. Specific examples of the anions include, but are not limited to, trifluoromethanesulfonate anion, tetrafluoroborate anion, hexafluorophosphate anion, difluoromethanesulfonylimide anion, hydrogen sulfate anion, ethyl sulfate anion, and p-toluenesulfonate anion. Specific examples of the ionic liquid may include, but are not limited to: 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-2,3-dimethylimidazolium trifluoromethanesulfonate, 1-octyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate, 1-propyl-2,3-methylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-di ... The imidazole bis(trifluoromethanesulfonyl)imide salt, 1,3-diethylimidazole bis(trifluoromethanesulfonyl)imide salt, 1-propyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, 1-hexyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, 1,2-dimethyl-3-propylimidazole bis(trifluoromethanesulfonyl)imide, 1-ethyl-2,3-dimethylimidazole bis(fluoromethanesulfonyl)imide salt, N-butylpyridine tetrafluoroborate, hexyltriethylammonium bis(trifluoromethanesulfonyl)imide salt, methyltrioctylphosphonium bis(trifluoromethanesulfonyl)imide salt, N-butyl-N-methylpyrrolidine bis(fluoromethanesulfonyl)imide salt, N-butyl-N-methylpyrrolidine trifluoromethanesulfonate, and N-propyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imide salt.

[0033] In this invention, specific examples of the silane coupling agent include, but are not limited to: 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, At least one of 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 3-isocyanate propyltrimethoxysilane.

[0034] In this invention, the polar solvent compound may be selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxymethane, 1,3-dimethoxypropane, 1,3-dioxolane, ethoxymethoxyethane, poly(ethylene glycol) dimethyl ether, poly(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether, poly(ethylene glycol) methyl ether acrylate, poly(ethylene glycol) diglycidyl ether, poly(ethylene glycol) ethyl ether methacrylate, polyethylene glycol-bis(2-ethylhexanoate), poly(ethylene glycol) octyl ether, poly(ethylene glycol) phenyl ether acrylate, poly(ethylene glycol) tetrahydrofurfuryl ether, and poly(ethylene glycol) methyl ether toluenesulfonate.

[0035] In this invention, the catalyst may be at least one of the following: dibutyltin dilaurate, stannous octoate, zinc isooctanoate, bismuth isooctanoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine, and 2,2-dimorpholinodiethyl ether.

[0036] In this invention, the desiccant may be at least one of molecular sieve desiccants, oxazolidine desiccant, p-toluenesulfonyl isocyanate, and triethyl orthoformate.

[0037] The method for preparing the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by the present invention includes mixing a siloxane-modified polyurethane prepolymer and a modified filler composition, along with an optional catalyst and a water absorbent, uniformly to obtain the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive.

[0038] The present invention does not particularly limit the mixing method, and the ingredients can be added and mixed in any order. In a preferred embodiment, the mixing step includes:

[0039] S31. The polyol compound and optional dehydrating agent are vacuum stirred at 100-200 r / min at 100-120℃ for 1-5 h, and then cooled to 70-90℃ to obtain the pretreated product.

[0040] S32. Add a polyisocyanate compound and an optional catalyst to the pretreated product and stir under vacuum at 70-90°C and 100-200 r / min for 1-5 h to obtain a polyurethane prepolymer with isocyanate double end capping.

[0041] S33. The isocyanate-terminated polyurethane prepolymer and a monothiol silane compound are reacted under vacuum at 70-90°C and 100-200 r / min for 1-5 h to obtain a siloxane-modified polyurethane prepolymer.

[0042] S34. The siloxane-modified polyurethane prepolymer and the modified filler composition are stirred under vacuum at 70-90°C and 100-200 r / min for 0.5-2 h to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive.

[0043] In the preparation process of the above-mentioned electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive, in step S31, the temperature of the vacuum stirring dehydration is 100-120℃, such as 100℃, 102℃, 104℃, 106℃, 108℃, 110℃, 112℃, 114℃, 116℃, 118℃, 120℃ or any value between them; the rotation speed is 100-200 r / min, such as 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 r / min or any value between them; the time is 1-5h, such as 1h, 2h, 3h, 4h, 5h or any value between them.

[0044] In the preparation process of the above-mentioned electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive, in step S32, the temperature of the vacuum stirring reaction is 70-90℃, such as 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃ or any value between them; the rotation speed is 100-200 r / min, such as 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 r / min or any value between them; the time is 1-5h, such as 1h, 2h, 3h, 4h, 5h or any value between them.

[0045] In the preparation process of the above-mentioned electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive, in step S33, the temperature of the vacuum stirring reaction is 70-90℃, such as 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃ or any value between them; the rotation speed is 100-200 r / min, such as 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 r / min or any value between them; the time is 1-5h, such as 1h, 2h, 3h, 4h, 5h or any value between them.

[0046] In the preparation process of the above-mentioned electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive, in step S34, the temperature of the vacuum stirring reaction is 70-90℃, such as 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃ or any value between them; the rotation speed is 100-200 r / min, such as 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 r / min or any value between them; the time is 0.5-2h, such as 0.5h, 0.8h, 1h, 1.2h, 1.5h, 1.8h, 2h or any value between them.

[0047] The present invention also provides the application of the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive in the bonding of electronic products.

[0048] The present invention will be described in detail below through embodiments.

[0049] The bonding substrate for the electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by this invention is a conductive substrate.

[0050] The present invention will now be described in detail through examples and comparative examples.

[0051] In the following examples and comparative examples, the parts of each raw material refer to parts by weight.

[0052] Preparation Example 1: Modified Filler Composition

[0053] By weight, 9.88 parts of 1-propyl-3-methylimidazolium tetrafluoroborate, 6.17 parts of propylene carbonate, and 3.70 parts of 3-aminopropyltrimethoxysilane were added to a reactor and heated to 110°C. The reactor was then vacuum dehydrated for 2 hours under stirring at 150 r / min. 40.25 parts of alumina (Foshan Weikede Materials, GTC-21K) with a particle size of 8-10 μm and 40.0 parts of magnesium oxide (Hangzhou Hengna New Materials, HN-Mg50D) with a particle size of 30-50 nm were added to the reactor and vacuum dehydrated for 4 hours under stirring at 110°C and 150 r / min to obtain modified filler composition A-1, which was then vacuum sealed and stored for later use.

[0054] Preparation Example 2: Modified Filler Composition

[0055] By weight, 11.90 parts of 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 4.0 parts of 3-epoxypropoxypropyltrimethoxysilane were added to a reactor and heated to 110°C. The reactor was then vacuum dehydrated for 2 hours under stirring at 150 r / min. 63.33 parts of alumina (Foshan Weikede Materials, GTC-31K) with a particle size of 6-9 μm and 20.0 parts of boron nitride (Shanghai Baitu, GBN-60) with a particle size of 60-75 μm were added to the reactor and vacuum dehydrated for 4 hours under stirring at 110°C and 150 r / min to obtain modified filler composition A-2, which was then vacuum sealed and stored for later use.

[0056] Preparation Example 3: Modified Filler Composition

[0057] By weight, 7.69 parts of hexyltriethylammonium bis(trifluoromethanesulfonyl)imide salt, 4.62 parts of poly(ethylene glycol) diglycidyl ether, and 3.08 parts of vinyltrimethoxysilane were added to a reactor and heated to 110°C. The mixture was then vacuum dehydrated for 2 hours under stirring at 150 rpm. 34.32 parts of alumina (Foshan Weikede Materials, GTC-066B) with a particle size of 8-10 μm and 50.30 parts of alumina (Foshan Weikede Materials, DR-50) with a particle size of 2.5-4.0 μm were added to the reactor. After vacuum dehydration for 4 hours under stirring at 110°C and 150 rpm, modified filler composition A-3 was obtained and vacuum-sealed for later use.

[0058] Preparation Example 4: Modified Filler Composition

[0059] By weight, 6.82 parts of lithium bis(trifluoromethanesulfonyl)imide, 11.36 parts of ethylene carbonate, and 5.68 parts of 3-isocyanate propyltrimethoxysilane were added to a reactor and heated to 110°C. The reactor was then vacuum dehydrated for 2 hours under stirring at 150 r / min. 33.12 parts of magnesium oxide (Hangzhou Hengna New Materials, HN-Mg50D) with a particle size of 30-50 nm and 43.02 parts of alumina (Foshan Weikede Materials, GTC-066B) with a particle size of 8-10 μm were added to the reactor and vacuum dehydrated for 4 hours under stirring at 110°C and 150 r / min to obtain modified filler composition A-4, which was then vacuum sealed and stored for later use.

[0060] Preparation Example 5: Modified Filler Composition

[0061] By weight, 8.86 parts of lithium tetrafluoroborate, 10.13 parts of polyethylene glycol-bis(2-ethylhexanoate), and 5.06 parts of 3-mercaptopropyltrimethoxysilane were added to a reactor and heated to 110°C. The reactor was then vacuum dehydrated for 2 hours under stirring at 150 r / min. 60.53 parts of alumina (Foshan Weikede Materials, GTC-21K) with a particle size of 8-10 μm and 15.42 parts of boron nitride (Shanghai Baitu, GBN-60) with a particle size of 60-75 μm were added to the reactor and vacuum dehydrated for 4 hours under stirring at 110°C and 150 r / min to obtain modified filler composition A-5, which was then vacuum sealed and stored for later use.

[0062] Comparative Preparation Example 1: Modified Filler Composition

[0063] The modified filler composition was prepared according to the method described in Preparation Example 3, except that the hexyltriethylammonium bis(trifluoromethanesulfonyl)imide salt in Preparation Example 3 was removed, as follows:

[0064] By weight, 4.62 parts of poly(ethylene glycol) diglycidyl ether and 3.08 parts of vinyltrimethoxysilane were added to a reactor and heated to 110°C. The mixture was then vacuum dehydrated for 2 hours under stirring at 150 r / min. 34.32 parts of alumina (Foshan Weikede Material, GTC-066B) with a particle size of 8-10 μm and 50.30 parts of alumina (Foshan Weikede Material, DR-50) with a particle size of 2.5-4.0 μm were added to the reactor and vacuum dehydrated for 4 hours under stirring at 110°C and 150 r / min to obtain modified filler composition C-1, which was then vacuum sealed and stored for later use.

[0065] Comparative Preparation Example 2: Modified Filler Composition

[0066] The modified filler composition was prepared according to the method described in Preparation Example 1, except that 3-aminopropyltrimethoxysilane was removed from Preparation Example 1, as follows:

[0067] By weight, 9.88 parts of 1-propyl-3-methylimidazolium tetrafluoroborate and 6.17 parts of propylene carbonate were added to a reactor and heated to 110°C. The mixture was then vacuum dehydrated for 2 hours under stirring at 150 r / min. 40.25 parts of alumina (Foshan Weikede Materials, GTC-21K) with a particle size of 8-10 μm and 40.0 parts of magnesium oxide (Hangzhou Hengna New Materials, HN-Mg50D) with a particle size of 30-50 nm were added to the reactor and vacuum dehydrated for 4 hours under stirring at 110°C and 150 r / min to obtain modified filler composition C-2, which was then vacuum sealed and stored for later use.

[0068] Example 1

[0069] By weight, 4.88 g (9.763 mmol) of polyhexanediol adipate with a number average molecular weight of 1000, 4.88 g (9.763 mmol) of polyoxypropylene ether diol with a number average molecular weight of 1000, and 0.5 g of water-absorbing agent Additive were added. TI was heated to 110°C and vacuum dehydrated for 2 hours under stirring at 150 rpm. Then, it was cooled to 80°C, and 5.86 g (46.863 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 0.2 g of stannous octoate were added. The mixture was stirred at 150 rpm for 2 hours. Then, 2.68 g (13.668 mmol) of 3-mercaptopropyltrimethylsilane was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 2 hours. Finally, 81.0 g of modified filler composition A1 was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 1 hour and then discharged to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 0.57%. The adhesive was then vacuum-sealed and stored.

[0070] Example 2

[0071] By weight, 4.09 g (8.185 mmol) of polybutylene adipate diol with a number average molecular weight of 1000, 4.09 g (8.185 mmol) of polytetrahydrofuran ether diol with a number average molecular weight of 1000, and 0.2 g of water-absorbing agent Additive were added. OF was heated to 110℃ and vacuum dehydrated for 2 hours under stirring at 150 r / min. Then, it was cooled to 80℃, and 5.36 g (40.927 mmol) of 4,4-diisocyanate dicyclohexylmethane (HMDI) and 0.5 g of dibutyltin dilaurate were added. The mixture was stirred at 150 r / min for 2 hours. Then, 1.75 g (7.367 mmol) of 3-mercaptopropyltriethoxysilane was added. The mixture was stirred at 80℃ and 150 r / min under vacuum for 2 hours. Finally, 84.0 g of modified filler composition A2 was added. The mixture was stirred at 80℃ and 150 r / min under vacuum for 1 hour and then discharged to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 0.72%. The adhesive was then vacuum-sealed and stored.

[0072] Example 3

[0073] By weight, 14.27 g (4.758 mmol) of polytetrahydrofuran ether glycol with a number average molecular weight of 3000, 14.27 g (4.758 mmol) of polycaprolactone glycol with a number average molecular weight of 2000, and 0.6 g of water-absorbing agent Siliporite SA1702 were heated to 110 °C and vacuum dehydrated for 2 h under stirring at 150 r / min; then cooled to 80 °C, and 3.52 g (20.936 mmol) of hexamethylene diisocyanate (HDI) and 1.1 g of... 2,2-Dimorpholinodiethyl ether was reacted at 150 r / min for 2 h with stirring. 1.23 g (6.852 mmol) of 3-mercaptopropylmethyldimethoxysilane was added, and the mixture was stirred under vacuum at 80 °C and 150 r / min for 2 h. Then, 65.0 g of modified filler composition A3 was added, and the mixture was stirred under vacuum at 80 °C and 150 r / min for 1 h before being discharged to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 0.67%. The adhesive was stored under vacuum sealing.

[0074] Example 4

[0075] By weight, 3.09 g (3.086 mmol) of poly(1,6-hexanediol carbonate) diol with a number average molecular weight of 1000, 3.09 g (3.086 mmol) of poly(butylene adipate) diol with a number average molecular weight of 1000, and 0.2 g of water-absorbing agent Additive were added. TI was heated to 110°C and vacuum dehydrated for 2 hours under stirring at 150 rpm. Then, it was cooled to 80°C, and 2.74 g (12.345 mmol) of isophorone diisocyanate (IPDI) and 1.3 g of zinc isooctanoate were added. The mixture was stirred at 150 rpm for 2 hours. Then, 1.59 g (6.667 mmol) of 3-mercaptopropyltriethoxysilane was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 2 hours. Finally, 88.0 g of modified filler composition A4 was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 1 hour and then discharged to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 0.24%. The adhesive was then vacuum-sealed and stored.

[0076] Example 5

[0077] By weight, 7.57 g (3.783 mmol) of polybutylene succinate diol with a number average molecular weight of 2000, 7.57 g (3.783 mmol) of polycaprolactone diol with a number average molecular weight of 2000, and 0.4 g of water-absorbing agent Additive were added. OF was heated to 110℃ and vacuum dehydrated for 2 hours under stirring at 150 r / min; then cooled to 80℃, and 3.78 g (15.134 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 0.2 g of bismuth isooctanoate were added. The mixture was stirred at 150 r / min for 2 hours, and then 1.48 g (7.567 mmol) of 3-mercaptopropyltrimethylsilane was added. The mixture was stirred at 80℃ and 150 r / min under vacuum for 2 hours. Finally, 79.0 g of modified filler composition A5 was added, and the mixture was stirred at 80℃ and 150 r / min under vacuum for 1 hour before being discharged to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 0.32%. The adhesive was then vacuum-sealed and stored.

[0078] Comparative Example 1

[0079] By weight, 29.2 g (14.6 mmol) of polyoxypropylene ether diol with a number average molecular weight of 2000, 29.2 g (14.6 mmol) of polyhexanediol adipate with a number average molecular weight of 2000, 8.0 g of lithium trifluoromethanesulfonate, 8.0 g of propylene carbonate, 10.0 g of acrylic resin BR113, 0.5 g of water-absorbing agent Additive OF, and 0.5 g of other ingredients were added. 3-Aminopropyltrimethoxysilane was heated to 110°C and vacuum dehydrated for 2 hours under stirring at 150 r / min. Then, it was cooled to 80°C, and 14.6 g (58.4 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 0.2 g of dibutyltin dilaurate were added. The mixture was reacted for 2 hours under stirring at 150 r / min and then discharged to obtain a reference electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive, wherein the isocyanate group content was 2.45%, and it was stored under vacuum sealing.

[0080] Comparative Example 2

[0081] The electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive was prepared according to the method described in Example 3, except that the electrolyte salt in Example 3 was removed, as detailed below:

[0082] By weight, 14.27 g (4.758 mmol) of polytetrahydrofuran ether glycol with a number average molecular weight of 3000, 14.27 g (4.758 mmol) of polycaprolactone glycol with a number average molecular weight of 2000, and 0.6 g of water-absorbing agent Siliporite SA1702 were heated to 110 °C and vacuum dehydrated for 2 h under stirring at 150 r / min; then cooled to 80 °C, and 3.52 g (20.936 mmol) of hexamethylene diisocyanate (HDI) and 1.1 g of... 2,2-Dimorpholinodiethyl ether was reacted at 150 r / min for 2 h with stirring. 1.23 g (6.852 mmol) of 3-mercaptopropylmethyldimethoxysilane was added, and the mixture was stirred under vacuum at 80 °C and 150 r / min for 2 h. Then, 65.0 g of modified filler composition C1 was added, and the mixture was stirred under vacuum at 80 °C and 150 r / min for 1 h before being discharged to obtain a reference single-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 0.67%. The adhesive was stored under vacuum sealing.

[0083] Comparative Example 3

[0084] The electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive was prepared according to the method described in Example 3, except that the components of the modified filler composition from Example 3 were directly added to the adhesive system, as detailed below:

[0085] By weight, 14.27 g (4.758 mmol) of polytetrahydrofuran ether glycol with a number average molecular weight of 3000, 14.27 g (4.758 mmol) of polycaprolactone glycol with a number average molecular weight of 2000, and 0.6 g of water-absorbing agent Siliporite SA1702 were heated to 110 °C and vacuum dehydrated for 2 h under stirring at 150 r / min; then cooled to 80 °C, and 3.52 g (20.936 mmol) of hexamethylene diisocyanate (HDI) and 1.1 g of... 2,2-Dimorpholinodiethyl ether was reacted at 150 rpm for 2 h with stirring. Then, 1.23 g (6.852 mmol) of 3-mercaptopropylmethyldimethoxysilane was added, and the mixture was stirred under vacuum at 80 °C and 150 rpm for 2 h. Finally, 5.0 g of hexyltriethylammonium bis(trifluoromethanesulfonyl)imide salt, 3.0 g of poly(ethylene glycol) diglycidyl ether, and 2.0 g of vinyltrimethoxysilane were added to the reaction vessel, and the mixture was heated to 110 °C and stirred at 150 rpm. Vacuum dehydration at 150 r / min for 2 h under stirring conditions; 22.31 g of alumina (Foshan Weikede Material, GTC-066B) with a particle size of 8-10 μm and 32.69 g of alumina (Foshan Weikede Material, DR-50) with a particle size of 2.5-4.0 μm were mixed under vacuum stirring at 80℃ and 150 r / min for 1 h and then discharged to obtain a reference single-component siloxane modified thermally conductive polyurethane hot melt adhesive, wherein the isocyanate group content is 0.67%, and it was stored under vacuum sealing.

[0086] Comparative Example 4

[0087] The electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive was prepared according to the method described in Example 1, except that the proportion of mercaptosiloxane-type components in the siloxane-terminated prepolymer was reduced so that the isocyanate group content in the resulting electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive exceeded 0.8%, as detailed below:

[0088] By weight, 5.62 g (11.245 mmol) of polyhexanediol adipate with a number average molecular weight of 1000, 5.62 g (11.245 mmol) of polyoxypropylene ether diol with a number average molecular weight of 1000, and 0.5 g of water-absorbing agent Additive were added. TI was heated to 110°C and vacuum dehydrated for 2 hours under stirring at 150 rpm. Then, it was cooled to 80°C, and 6.75 g (53.974 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 0.2 g of stannous octoate were added. The mixture was stirred at 150 rpm for 2 hours. Then, 0.31 g (1.574 mmol) of 3-mercaptopropyltrimethylsilane was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 2 hours. Finally, 81.0 g of modified filler composition A1 was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 1 hour and then discharged to obtain a reference electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 1.26%. The adhesive was then vacuum-sealed and stored.

[0089] Comparative Example 5

[0090] The electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive was prepared according to the method described in Example 1, except that 3-aminopropyltrimethoxysilane was removed from Example 1, as detailed below:

[0091] By weight, 4.88 g (9.763 mmol) of polyhexanediol adipate with a number average molecular weight of 1000, 4.88 g (9.763 mmol) of polyoxypropylene ether diol with a number average molecular weight of 1000, and 0.5 g of water-absorbing agent Additive were added. TI was heated to 110°C and vacuum dehydrated for 2 hours under stirring at 150 rpm. Then, it was cooled to 80°C, and 5.86 g (46.863 mmol) of 4,4'-diphenylmethane diisocyanate (MDI) and 0.2 g of stannous octoate were added. The mixture was stirred at 150 rpm for 2 hours. Then, 2.68 g (13.668 mmol) of 3-mercaptopropyltrimethylsilane was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 2 hours. Finally, 81.0 g of modified filler composition C2 was added. The mixture was stirred at 80°C and 150 rpm under vacuum for 1 hour and then discharged to obtain a reference electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive with an isocyanate group content of 0.57%. The adhesive was then vacuum-sealed and stored.

[0092] Test case

[0093] (1) Curing bubble behavior: The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive obtained in the examples and comparative examples was melted at 110°C. After melting, a film was coated on the release film using a 400μm scraper. The film was then placed in an oven at 25°C and 50% RH for 4 hours to cure. The appearance of the film was observed, and the presence or absence of bubbles was recorded. The results are shown in Table 1.

[0094] (2) Adhesive strength at different curing times (1h, 1d, 7d): The electrically removable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive obtained in the examples and comparative examples was dispensed at 110°C using a dispensing machine. A rectangular adhesive line of 25mm*4mm was applied to a stainless steel substrate. Then, another stainless steel substrate was bonded to the stainless steel substrate. After bonding, the samples were cured at 25°C and 50%RH for 1h, 1d, and 7d. Afterward, the bonded samples were run along the shear direction at a speed of 10mm / min using a universal testing machine until the bond failed. The maximum force value displayed by the instrument was recorded. The shear bond strength of the adhesive to the stainless steel substrate after different curing times was calculated based on the bond area. The results are shown in Table 1.

[0095] (3) Bonding strength after energization: The electrically removable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive obtained in the examples and comparative examples was applied at 110°C using a dispensing machine. A rectangular adhesive line of 25mm*4mm was applied to a stainless steel substrate. Then, another stainless steel substrate was bonded to the stainless steel substrate. After bonding, the sample was cured in an environment of 25°C and 50%RH for 48 hours. Then, the positive and negative wires of the DC power supply were clamped to both ends of the sheared sample, and energized at a certain voltage for a certain period of time. After energization, the sheared sample was removed. The prepared bonded sample was run along the shear direction at a speed of 10mm / min using a universal testing machine until the sample failed to bond. The maximum force value displayed by the instrument was recorded. The shear bond strength of the adhesive to the stainless steel substrate after energization was calculated based on the bonding area. The results are shown in Table 1.

[0096] (4) Thermal conductivity: The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive obtained in the examples and comparative examples was coated on a clean PET film and cured for 7 days at 25°C and 50%RH. Then the thermal conductivity was tested according to the method of GB / T11205-2009.

[0097] Table 1

[0098] As shown in Table 1, the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by this invention is bubble-free and has a high thermal conductivity, which facilitates faster heat transfer and helps the bonded components achieve rapid heat dissipation, reducing the impact of rapid heat increase on the operability and safety of electronic components. Based on practical experience, a bond strength below 2.0 MPa at room temperature indicates that the adhesive is detachable; otherwise, it is not. As shown in Table 1, the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive provided by this invention exhibits excellent detachable performance after being energized, with the bond strength significantly decreasing and even the adhesive potentially detaching completely.

[0099] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A detachable, one-component, siloxane-modified, thermally conductive polyurethane hot melt adhesive, characterized in that, The electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive contains a siloxane-modified polyurethane prepolymer and a modified filler composition, as well as an optional catalyst and a water-absorbing agent. The modified filler composition contains a thermally conductive filler, an electrolyte salt, a silane coupling agent, and an optional polar solvent compound. The isocyanate group content in the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive is 0.2% to 0.8%, and the mass ratio of the siloxane-modified polyurethane prepolymer to the modified filler composition is 1:(1.5 to 7.5). The adhesive strength of the electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive decreases by more than 80% after being energized at a voltage of 1 to 100V.

2. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 1, characterized in that, Based on the total weight of the electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive, the total content of the siloxane-modified polyurethane prepolymer and modified filler composition is 90-99.8%, the content of the catalyst is 0.1-5%, and the content of the water absorbent is 0.1-5%.

3. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 1, characterized in that, The siloxane-modified polyurethane prepolymer was prepared according to the following method: S11. A polyol compound and a polyisocyanate compound are optionally subjected to a first addition reaction in the presence of a catalyst to obtain a polyurethane prepolymer with isocyanate double-terminated ends. S12. The isocyanate-terminated polyurethane prepolymer is subjected to a second addition reaction with a monothiol silane compound to obtain a siloxane-modified polyurethane prepolymer.

4. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 3, characterized in that, The molar ratio of hydroxyl groups in the polyol compounds, isocyanate groups in the polyisocyanate compounds, and mercapto groups in the monothiol siloxane compounds is 1:(2-2.5):(0.3-0.9).

5. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 3, characterized in that, The polyol compound is selected from at least one of polyester polyols, polyether polyols, polycarbonate polyols, and polyalkylene polyols.

6. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 3, characterized in that, The polyisocyanate compound is selected from at least one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, hydrogenated phenyldiisocyanate, 1,5-naphthalene diisocyanate, 1,5-pentane diisocyanate, 1,4-phenyl diisocyanate, phenyldiisocyanate, tetramethylxylene diisocyanate, norbornene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, triphenyl thiophosphate, and 1,6,11-undecane triisocyanate.

7. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 3, characterized in that, The monothiol silane compound is selected from at least one of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane.

8. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 1, characterized in that, The modified filler composition was prepared according to the following method: S21. Electrolyte salt, silane coupling agent and optional polar solvent compound are vacuum stirred at 100-120℃ and 100-200 r / min for 1-5 h to obtain pretreated product. S22. The pretreated product and the thermally conductive filler are stirred under vacuum at 100-120°C and 100-200 r / min for 3-6 hours to obtain the modified filler composition.

9. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 8, characterized in that, The modified filler composition contains 70-85 parts by weight of thermally conductive filler, 5-15 parts by weight of electrolyte salt, 2-7 parts by weight of silane coupling agent, and 0-15 parts by weight of polar solvent compound.

10. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 8, characterized in that, The thermally conductive filler is selected from at least one of alumina, magnesium oxide, zinc oxide, nickel oxide, aluminum nitride, silicon nitride, boron nitride, and silicon carbide.

11. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 8, characterized in that, The electrolyte salt is an alkali metal salt and / or an ionic liquid.

12. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 8, characterized in that, The silane coupling agent is selected from 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-aminopropyltriethoxysilane. At least one of the following: methyl silane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 3-isocyanate propyltrimethoxysilane.

13. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 8, characterized in that, The polar solvent compound is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxymethane, 1,3-dimethoxypropane, 1,3-dioxolane, ethoxymethoxyethane, poly(ethylene glycol) dimethyl ether, poly(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether, poly(ethylene glycol) methyl ether acrylate, poly(ethylene glycol) diglycidyl ether, poly(ethylene glycol) ethyl ether methacrylate, polyethylene glycol-bis(2-ethylhexanoate), poly(ethylene glycol) octyl ether, poly(ethylene glycol) phenyl ether acrylate, poly(ethylene glycol) tetrahydrofurfuryl ether, and poly(ethylene glycol) methyl ether toluenesulfonate.

14. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 1, characterized in that, The catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, zinc isooctanoate, bismuth isooctanoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine, and 2,2-dimorpholinodiethyl ether.

15. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 1, characterized in that, The desiccant is selected from at least one of molecular sieve desiccant, oxazolidine desiccant, p-toluenesulfonyl isocyanate and triethyl orthoformate.

16. The method for preparing the electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 1, characterized in that, The method involves uniformly mixing a siloxane-modified polyurethane prepolymer and a modified filler composition, along with an optional catalyst and a desiccant, to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive.

17. The electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive according to claim 1, characterized in that, The mixing step includes: S31. The polyol compound and optional dehydrating agent are vacuum stirred at 100-120°C and 100-200 r / min for 1-5 h, and then cooled to 70-90°C to obtain the pretreated product. S32. Add a polyisocyanate compound and an optional catalyst to the pretreated product and stir under vacuum at 70-90°C and 100-200 r / min for 1-5 h to obtain a polyurethane prepolymer with isocyanate double end capping. S33. The isocyanate-terminated polyurethane prepolymer and a monothiol silane compound are reacted under vacuum at 70-90°C and 100-200 r / min for 1-5 h to obtain a siloxane-modified polyurethane prepolymer. S34. The siloxane-modified polyurethane prepolymer and the modified filler composition are stirred under vacuum at 70-90°C and 100-200 r / min for 0.5-2 h to obtain an electrically detachable one-component siloxane-modified thermally conductive polyurethane hot melt adhesive.

18. The application of the electrically detachable single-component siloxane-modified thermally conductive polyurethane hot melt adhesive of claim 1 in the bonding of electronic products.

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