An acrylate-modified polyurethane hot melt adhesive, and a preparation method and application thereof

Abstract

The present application belongs to the field of adhesive, and relates to an acrylate modified polyurethane hot melt adhesive as well as a preparation method and application thereof. The acrylate modified polyurethane hot melt adhesive has a viscosity range of 1000-150000 cps at 25 DEG C and an attenuation rate of bonding strength of above 80% after power supply at a voltage of 1-100 V, and contains a polyurethane prepolymer mixture, an acrylate compound, an ionic liquid and a photoinitiator. The polyol structural unit contained in the polyurethane prepolymer mixture is derived from a low-viscosity polyol compound with a glass transition temperature below 0 DEG C and a melting point below 40 DEG C, and the mass ratio of the polyurethane prepolymer mixture to the acrylate compound is (1.5-9):1. The polyurethane hot melt adhesive provided by the present application has a low melt viscosity, can be dispensed at room temperature, has high initial bonding strength and final bonding strength, has a fast curing speed, and has a disassembling function under power supply condition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of adhesives, and particularly relates to an acrylate modified polyurethane hot melt adhesive as well as a preparation method and application thereof. BACKGROUND

[0002] In electronic products such as smart phones, tablet computers, smart watches, TWS earphones, etc., reactive polyurethane hot melt adhesives are often used to bond and fix the parts of the electronic products. The parts of the electronic products bonded by the reactive polyurethane hot melt adhesives often have high value. When there are situations such as poor assembly, product after-sales repair, and recycling of valuable electronic product parts, the bonded parts often need to be disassembled. Therefore, the adhesive is often required to have excellent bonding reliability and the function of being easy to disassemble under certain conditions.

[0003] The reactive polyurethane hot melt adhesive mainly uses isocyanate-terminated oligomers as the main body. The isocyanate groups in the isocyanate-terminated oligomers can react with moisture in the air. After complete curing, a cross-linked chemical structure is formed, thereby realizing high bonding strength. However, the covalent bond obtained by the reaction of the isocyanate groups with moisture is irreversible, and the cross-linked structure is difficult to be destroyed. After complete curing, it is usually difficult to disassemble the adhesive. If the bonded materials need to be separated, a large external force, high temperature, chemical reagents, etc. are often required, and the bonded materials may be damaged during the disassembly of the adhesive, causing great economic losses.

[0004] In recent years, there are also technologies that add ionic liquids or alkali metal salts and solventized matrices to polyurethane hot melt adhesives to endow the polyurethane hot melt adhesives with the function of being disassembled under the condition of being electrified. However, the existing electrically disassemblable polyurethane hot melt adhesives have the function of being disassembled under the condition of being electrified. However, due to the high melt viscosity of such polyurethane hot melt adhesives, they are solid substances at room temperature, and usually need to be heated to a melt temperature (usually 90℃ to 160℃) or higher to be extruded and applied. At this time, a professional heating and application device is usually required, but this will not only increase the cost of using the adhesive, but also greatly limit the application scenarios of such polyurethane hot melt adhesives, such as homes and repair markets where it is inconvenient to provide heating equipment, thereby greatly limiting the widespread application and promotion of such polyurethane hot melt adhesives. In addition, the existing electrically disassemblable polyurethane hot melt adhesives have certain electrically disassemblable function, but the final bonding strength is low, the reliability is poor, and the curing speed is slow. There is a big performance gap with traditional reactive polyurethane hot melt adhesives, and it is difficult to meet the performance requirements of actual application scenarios.

[0005] The existing acrylate modified polyurethane hot melt adhesive is a UV and moisture dual-curable polyurethane hot melt adhesive prepared by modifying the polyurethane hot melt adhesive by physical blending or chemical modification of acrylate compounds. The UV curing speed is fast. After UV irradiation, the acrylate components in the acrylate modified polyurethane hot melt adhesive can be quickly photocured, effectively improving the slow defect of the polyurethane hot melt adhesive relying on moisture curing. However, the acrylate modified polyurethane hot melt adhesive still has many problems such as difficult disassembly after curing and difficult application at room temperature.

[0006] In summary, there is an urgent need to develop a kind of adhesive with low melt viscosity, dispensing at room temperature, high initial and final bonding strength, fast curing speed and electric disassembly function to meet the application needs of the market. SUMMARY

[0007] The first object of the present application is to provide an acrylate modified polyurethane hot melt adhesive with low melt viscosity, dispensing at room temperature, high initial and final bonding strength, fast curing speed and electric disassembly function.

[0008] The second object of the present application is to provide a preparation method of the above-mentioned acrylate modified polyurethane hot melt adhesive.

[0009] The third object of the present application is to provide the application of the above-mentioned acrylate modified polyurethane hot melt adhesive in electronic product bonding.

[0010] Specifically, the acrylate modified polyurethane hot melt adhesive provided by the present application has a viscosity range of 1000-150000 cps at 25℃ and an adhesion strength decay rate of more than 80% after power supply at a voltage of 1-100V. The acrylate modified polyurethane hot melt adhesive contains a polyurethane prepolymer mixture, an acrylate compound, an ionic liquid and a photoinitiator. The prepolymers contained in the polyurethane prepolymer mixture have isocyanate end-capping at both ends. The polyol structural units contained in the polyurethane prepolymer mixture are derived from low-viscosity polyol compounds with a glass transition temperature below 0℃ and a melting point below 40℃. The mass ratio of the polyurethane prepolymer mixture to the acrylate compound is (1.5-9):1.

[0011] The preparation method of the acrylate modified polyurethane hot melt adhesive provided by the present application comprises:

[0012] S1, dehydrating the low-viscosity polyol compound, the ionic liquid and optionally the rheological modifier, the silane coupling agent and the water absorption agent to obtain a pretreated product;

[0013] S2, stirring and reacting the pretreated product, the polyisocyanate compound and the optional catalyst at 70-90°C for 1-5h to obtain a prepolymer containing a polyurethane prepolymer mixture;

[0014] S3, mixing the prepolymer with the acrylate compound and the photoinitiator uniformly to obtain the acrylate-modified polyurethane hot melt adhesive.

[0015] The inventors of the present application have found through in-depth and extensive research that the polyurethane polymer with isocyanate functional groups selected by the existing electrically disassemblable polyurethane hot melt adhesive is a polyurethane prepolymer obtained by reacting a polyol compound with an excess of a polyisocyanate compound. The molar equivalent ratio of isocyanate groups in the polyisocyanate compound to hydroxyl groups in the polyol compound is usually set at (1.5-2.5):1 (i.e. the molar ratio of NCO / OH is (1.5-2.5):1). The polyurethane prepolymer prepared according to this stoichiometric relationship has a low isocyanate content, a large molecular weight of the polyurethane prepolymer, and a large interaction force between the molecular chains, thereby resulting in a final polyurethane prepolymer having a high melt viscosity, which is not easy to dispense at room temperature. In addition, some polyol compounds used in the polyurethane prepolymer with isocyanate functional groups have strong crystallinity or a high glass transition temperature (Tg) at room temperature. The polyurethane prepolymer prepared by reacting the room temperature crystalline polyol or the high Tg polyol with the isocyanate compound is usually a solid substance at room temperature. Therefore, the electrically disassemblable polyurethane hot melt adhesive prepared according to the traditional method is usually a solid substance at room temperature, which needs to be heated to above the melting point (90-160°C) to be molten and applied, greatly increasing the threshold for using such polyurethane hot melt adhesive, increasing the cost of equipment for using the adhesive, and also increasing the risk of scalding for the operator during the application process.

[0016] The existing electrically disassemblable polyurethane hot melt adhesive is prepared by adding ionic liquid or alkali metal salt and solventized matrix in the polyurethane hot melt adhesive, using the Faraday reaction of anions and cations in the ionic liquid or alkali metal salt under the condition of electricity to give the polyurethane hot melt adhesive disassemblable function under the condition of electricity. Among them, the liquid substances such as ionic liquid and solventized matrix introduced in the polyurethane hot melt adhesive are beneficial to realize the electric disassembly function, but such liquid substances cannot participate in the curing of the polyurethane hot melt adhesive, and still exist in the initial low viscosity state after the curing of the polyurethane hot melt adhesive, thus having a certain negative effect on the final adhesive strength of the adhesive. In addition, since the equivalent ratio of isocyanate to hydroxyl in the isocyanate-terminated polyurethane prepolymer is low (the equivalent ratio of NCO / OH is between 1.5 and 2.5), the isocyanate content of the finally prepared polyurethane prepolymer is low, thus the crosslinking density of the polyurethane prepolymer after the final wet curing is low, so that the adhesive strength of the adhesive after curing is low, and after the negative effect of the liquid components such as ionic liquid and solventized matrix, the adhesive strength will be further reduced. Therefore, although the ionic liquid or alkali metal salt combined with the solventized matrix can be added to the polyurethane hot melt adhesive to prepare the electrically disassemblable polyurethane hot melt adhesive, the final adhesion is still greatly insufficient, which is not conducive to the application and promotion of such products.

[0017] The existing acrylate-modified polyurethane hot melt adhesive can improve the curing speed, effectively improve the slow curing speed of polyurethane hot melt adhesive relying on moisture, but the adhesive force formed after curing is relatively strong, and it is difficult to achieve the function of easy disassembly. In addition, the current adhesive that can realize electrical disassembly generally requires the bonded substrate to be conductive. Typically, such conductive substrates are opaque substrates such as stainless steel, aluminum, copper and other metals. For opaque substrates, it is difficult to use UV light-curable adhesives and UV moisture-curable adhesives that generally use acrylate compounds as the main component. This is because the adhesive composition with light-curable components as the main component will instantly cure after UV light exposure, and the re-adhesion is quickly lost after UV light exposure, so most UV light-curable adhesives or UV moisture-curable adhesives can only be used for bonding at least one light-transmitting substrate. Therefore, even if the electrical disassembly composition known to provide the electrical disassembly function is directly added to the existing UV acrylate adhesive or UV moisture-curable adhesive with UV acrylate compounds as the main component, it is also difficult to be directly applied to the bonding of opaque metal substrates. In addition, the existing part of the acrylate-modified polyurethane hot melt adhesive that can be used for bonding of opaque substrates mainly uses polyurethane prepolymers as the main component, and a small amount of acrylate compounds for modification. Although this type of acrylate-modified polyurethane hot melt adhesive can be used for bonding of opaque substrates, the melt viscosity of this type of acrylate-modified polyurethane hot melt adhesive is relatively high, and a heating device is usually required for dispensing. The main reason why this type of acrylate-modified polyurethane hot melt adhesive is difficult to apply at room temperature is that on the one hand, the proportion of low-viscosity acrylate compounds is small, and the dilution capacity of the polyurethane prepolymer main body is weak, and on the other hand, the polyurethane prepolymer itself still uses some polyols with relatively high glass transition temperature and / or strong crystallinity at room temperature during preparation. The melt viscosity of such polyurethane prepolymer main body itself is relatively high. Therefore, the acrylate-modified polyurethane hot melt adhesive prepared finally is difficult to melt and dispense at room temperature, and a heating device is required for dispensing.

[0018] The key of the present application is to prepare an isocyanate double-terminated polyurethane prepolymer mixture by reacting a polyol compound with low glass transition temperature and low crystallinity at room temperature with an excess of an isocyanate compound, and innovatively introducing an acrylate compound and an ionic liquid into the polyurethane prepolymer mixture, while strictly controlling the ratio between the polyurethane prepolymer mixture and the acrylate compound, so as to endow the finally obtained acrylate modified polyurethane hot melt adhesive with the advantages of low melt viscosity, dispensing at room temperature, high initial bonding strength and final bonding strength, fast curing speed and electrically detachable performance. It is speculated that the reason may be that the acrylate compound and the ionic liquid have good flowability at room temperature and have low viscosity, and the simultaneous introduction of the acrylate compound and the ionic liquid into the polyurethane hot melt adhesive can realize the "first" reduction of the system viscosity, improve the flowability of the adhesive at room temperature, and the selection of a low-viscosity polyol compound with a glass transition temperature below 0℃ and a melting point below 40℃ can reduce the melt viscosity of the polyurethane prepolymer at room temperature from the root, realizing the "second" reduction of the system viscosity, that is, the present application reduces the viscosity of the system from two dimensions of the synergistic external viscosity reduction of the acrylate compound / ionic liquid and the internal viscosity reduction of the polyurethane prepolymer, which is conducive to the direct application of the polyurethane hot melt adhesive at room temperature, greatly reduces the application threshold of the polyurethane hot melt adhesive, reduces the equipment cost required for the application of the polyurethane hot melt adhesive, and effectively avoids the risk of the operator being scalded during the use of the adhesive. In addition, the acrylate compound can rapidly undergo a free radical polymerization reaction after UV irradiation, rapidly establishing a high initial bonding strength, and then the polyurethane prepolymer further improves the bonding strength of the system through a moisture curing reaction, and after curing, a polyurethane-polyacrylate interpenetrating network structure is formed, endowing the polyurethane hot melt adhesive with high final bonding strength. In addition, the ionic liquid can undergo a Faraday reaction after being electrified, and the introduction of the ionic liquid into the acrylate modified polyurethane hot melt adhesive can endow it with electrically detachable performance. In addition, as described above, the polyurethane hot melt adhesive provided by the present application relies on the acrylate compound to improve the initial bonding strength in the early stage, and relies on the polyurethane-polyacrylate interpenetrating network structure to improve the final bonding strength in the later stage, so that even if affected by the un-cured ionic liquid, it can still maintain a relatively high initial bonding strength and final bonding strength. DETAILED DESCRIPTION

[0019] The acrylate modified polyurethane hot melt adhesive provided by the present application has a viscosity range of 1000-150000 cps at 25℃, and specifically can be 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 30000, 50000, 70000, 90000, 110000, 130000, 150000 cps or any value therebetween.

[0020] The acrylate modified polyurethane hot melt adhesive provided by the present application has a decay rate of bonding strength of 80% or more after being powered on at a voltage of 1-100V, and can be specifically 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 99%, 100% or any value therebetween. The voltage required for the acrylate modified polyurethane hot melt adhesive to be powered on and disassembled is preferably 1-100V, and can be specifically 1V, 3V, 5V, 7V, 9V, 10V, 20V, 30V, 40V, 50V, 60V, 70V, 80V, 90V, 100V or any value therebetween; the time required for power on is preferably 1s-60min, such as 1s, 2s, 5s, 15s, 30s, 40s, 50s, 1min, 5min, 10min, 15min, 20min, 30min, 40min, 50min, 60min or any value therebetween.

[0021] In the present application, the acrylate modified polyurethane hot melt adhesive contains a polyurethane prepolymer mixture, an acrylate compound, an ionic liquid and a photoinitiator. The introduction of polyol structural units with weak crystallinity or low glass transition temperature in the polyurethane prepolymer mixture and the addition of the acrylate compound and the ionic liquid together reduce the viscosity of the system, imparting the performance of direct gluing at room temperature. In addition, the introduction of the acrylate compound improves the initial bonding strength and curing speed of the polyurethane hot melt adhesive, the control of the mass ratio of the polyurethane prepolymer mixture to the acrylate compound improves the final bonding strength, and the introduction of the ionic liquid imparts the electrically disassemblable performance of the polyurethane hot melt adhesive. The polyol structural units contained in the polyurethane prepolymer mixture are derived from low-viscosity polyol compounds. The glass transition temperature (Tg) of the low-viscosity polyol compound is 0°C or lower, and can be 0°C, -2°C, -4°C, -6°C, -8°C, -10°C, -12°C, -14°C, -16°C, -18°C, -20°C, -22°C, -24°C, -26°C, -28°C, -30°C, -32°C, -34°C, -36°C, -38°C, -40°C, etc. The melting point of the low-viscosity polyol compound is 40°C or lower, and can be 40°C, 38°C, 36°C, 34°C, 32°C, 30°C, 28°C, 26°C, 24°C, 22°C, 20°C, 18°C, 16°C, 14°C, 12°C, 10°C, 8°C, 6°C, 4°C, 2°C, 0°C, -5°C, -10°C, -15°C, -20°C, -30°C, etc. The mass ratio of the polyurethane prepolymer mixture to the acrylate compound is (1.5-9.0):1, and can be 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, 7.5:1, 8:1, 8.5:1, 9:1 or any value therebetween. In the present application, the term "polyurethane prepolymer mixture" refers to a prepolymer obtained by the addition reaction of a polyisocyanate compound and a low-viscosity polyol compound. Since the prepolymer contains polymers of different molecular weights and possibly unreacted monomers, it is a mixture of multiple substances, and is therefore referred to as "polyurethane prepolymer mixture".

[0022] The acrylate modified polyurethane hot melt adhesive provided by the present application is a liquid or paste at room temperature, has low melt viscosity, can be point-glued at room temperature, has high initial and final bonding strength, fast curing speed and electrically disassemblable performance.

[0023] In a preferred embodiment, the raw materials for preparing the acrylate-modified polyurethane hot melt adhesive comprise a polyisocyanate compound, a low-viscosity polyol compound, an acrylate compound, an ionic liquid, a photoinitiator, and optionally a rheology modifier, a silane coupling agent, a water absorbent, and a catalyst, the molar equivalent ratio of isocyanate groups in the polyisocyanate compound to hydroxyl groups in the low-viscosity polyol compound being (2.5-5): 1. Specifically, the molar equivalent ratio of isocyanate groups in the polyisocyanate compound to hydroxyl groups in the low-viscosity polyol compound can be 2.5: 1, 3: 1, 3.5: 1, 4: 1, 4.5: 1, 5: 1, or any value therebetween.

[0024] In the present application, the mass ratio of the total content of the polyisocyanate-based compound and the low-viscosity polyol-based compound to the content of the ionic liquid is preferably (3-40): 1, and can be specifically 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, 20:1, 22:1, 25:1, 28:1, 30:1, 32:1, 35:1, 38:1, 40:1, or any value therebetween. The mass ratio of the acrylate-based compound to the ionic liquid is preferably (0.3-18): 1, and can be specifically 0.3:1, 0.5:1, 1:1, 2:1, 5:1, 8:1, 10:1, 12:1, 15:1, 18:1, or any value therebetween. The mass ratio of the photoinitiator to the ionic liquid is preferably (0.005-2.5): 1, and can be specifically 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, or any value therebetween. The mass ratio of the catalyst to the content of the ionic liquid is preferably (0.005-1): 1, and can be specifically 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, or any value therebetween. The mass ratio of the rheology modifier to the ionic liquid is preferably (0-5): 1, and can be specifically 0, 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any value therebetween. The mass ratio of the silane coupling agent to the ionic liquid is preferably (0-1.5): 1, and can be specifically 0, 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, or any value therebetween. The mass ratio of the water-absorbing agent to the ionic liquid is preferably (0-1): 1, and can be specifically 0, 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, or any value therebetween.

[0025] In a preferred embodiment, the total content of the polyisocyanate compound and the low-viscosity polyol compound is 45-80%, such as 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value therebetween, based on the total weight of the raw materials for preparing the acrylate-modified polyurethane hot melt adhesive; the content of the acrylate compound is 5-35%, such as 3%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, or any value therebetween; the content of the ionic liquid is 2-15%, such as 2%, 5%, 8%, 10%, 12%, 15%, or any value therebetween; the content of the photoinitiator is 0.1-5%, such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or any value therebetween; the content of the rheology modifier is 2-10%, such as 2%, 5%, 8%, 10%, or any value therebetween; the content of the silane coupling agent is 0.1-3%, such as 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, or any value therebetween; the content of the water absorbent is 0.1-2%, such as 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, or any value therebetween; and the content of the catalyst is 0.1-2%, such as 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, or any value therebetween.

[0026] In the present application, the polyisocyanate compound is a compound having two or more isocyanate groups at the terminal of the molecular chain, and can specifically be an aromatic isocyanate and / or an aliphatic isocyanate, and specific examples thereof include, but are not limited to, 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 xylylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-pentane diisocyanate, 1,4-phenylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, norbornane dimethylene isocyanate, lysine diisocyanate, triphenylmethane triisocyanate, thiophosphoric acid triphenyl isocyanate, and 1,6,11-undecane triisocyanate.

[0027] In the present application, the number average molecular weight of the low viscosity polyol compound is preferably 400 to 6000 g / mol, such as 400, 500, 800, 1000, 1200, 1500, 1800, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000 g / mol or any value therebetween. The low viscosity polyol compound can be any of the various polyol compounds having a glass transition temperature of 0°C or less and a melting point of 40°C or less, and specific examples thereof include, but are not limited to, at least one of a liquid polyester polyol, a liquid polyether polyol, a liquid polycarbonate polyol, a liquid polycaprolactone polyol, a fatty acid dimer diol, a castor oil derivative polyol, and a hydroxyl-terminated polybutadiene polyol.

[0028] In the present application, the acrylate compound can be any of the various acrylate monomers that can be photocured, and examples thereof include at least one of stearyl acrylate, tetrahydrofurfuryl acrylate, dodecyl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, isooctyl acrylate, tridecyl acrylate, trimethylolpropane formal acrylate, methoxypolyethylene glycol monoacrylate, alkoxylated tetrahydrofurfuryl acrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate.

[0029] In the present application, the melting point of the ionic liquid is preferably 25°C or less, such as 25°C, 23°C, 20°C, 18°C, 15°C, 13°C, 10°C, 8°C, 5°C, 2°C, 0°C, -5°C, -10°C, -15°C, -20°C, -30°C, -40°C, and the like. The ionic liquid is composed of a cation and an anion. The cation is preferably selected from at least one of imidazole-based cations, pyrrole-based cations, quaternary ammonium salt-based cations, quaternary phosphonium salt-based cations, pyrrolidine-based cations, and piperidine-based cations. The anion is preferably selected from at least one of triflate anions, tetrafluoroborate anions, hexafluorophosphate anions, bisfluoromethanesulfonylimide anions, hydrogen sulfate anions, ethyl sulfate-based anions, and p-toluenesulfonate anions. Specific examples of the above ionic liquid can include, but are not limited to, at least one of 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium triflate, 1-ethyl-2,3-dimethylimidazolium triflate, 1-octyl-3-methylimidazolium triflate, 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-dimethylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-2,3-dimethylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1,3-diethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium bisfluorosulfonylimide, N-butylpyridinium tetrafluoroborate, hexyltriethylammonium bis(trifluoromethanesulfonyl)imide, methyltrioctylphosphonium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bisfluorosulfonylimide, N-butyl-N-methylpyrrolidinium triflate, and N-propyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide.

[0030] In the present application, the photoinitiator can be any of various compounds that absorb energy in the ultraviolet region or the visible region to generate radicals to initiate polymerization of the acrylic functional group, and examples thereof include at least one of benzophenone-based compounds, acetophenone-based compounds, acylphosphine oxide-based compounds, titanocene-based compounds, oxime ester-based compounds, benzoin ether-based compounds, and thioxanthone.

[0031] In the present application, the rheology modifier is preferably fumed silica, specific examples of which include, but are not limited to, at least one of AEROSIL A150, AEROSIL A200, AEROSIL A300, AEROSIL A380, AEROSIL R972, AEROSIL R974, AEROSIL R202, AEROSIL R812, HDK V15, HDK N20, HDK T30, HDK T40, HDK H13L, HDK H15, HDK H15L, HDK H16, HDK H17, HDK H18, HDK H2000, HDK H20, HDK H21, HDK H30, HDK H30RM, LM-150, M-5, E-5, EH-5, TS610, TS620, TS622, TS720, TS530, and TSUBOND. The specific surface area of the fumed silica is preferably 90 to 380 m 2 / g, specifically 90, 100, 120, 150, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380 m 2 / g, or any value therebetween.

[0032] In the present application, specific examples of the silane coupling agent include, but are not limited to, at least one of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 3-isocyanatepropyltrimethoxysilane.

[0033] In the present application, the water absorbing agent can be selected from at least one of molecular sieve desiccant, oxazolidine water removing agent, p-toluenesulfonylisocyanate, and triethyl orthoformate.

[0034] In the present application, the catalyst can be selected from at least one of dibutyltin dilaurate, stannous octoate, zinc isooctoate, bismuth isooctoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine, and 2,2-dimorpholinyl diethyl ether.

[0035] The preparation method of the acrylate modified polyurethane hot melt adhesive provided by the present application comprises the following steps: S1, dehydrating a low-viscosity polyol compound, an ionic liquid, and optionally a rheological modifier, a silane coupling agent, and a water absorption agent to obtain a pretreated product; S2, stirring and reacting the pretreated product, a polyisocyanate compound, and optionally a catalyst at 70-90 DEG C for 1-5 h to obtain a prepolymer containing a polyurethane prepolymer mixture; S3, uniformly mixing the prepolymer with an acrylate compound and a photoinitiator to obtain the acrylate modified polyurethane hot melt adhesive.

[0036] In the present application, in step S1, the dehydrating conditions preferably include a temperature of 100-120 DEG C, such as 100 DEG C, 102 DEG C, 104 DEG C, 106 DEG C, 108 DEG C, 110 DEG C, 112 DEG C, 114 DEG C, 116 DEG C, 118 DEG C, 120 DEG C, or any value therebetween; a rotation speed of 100-200 r / min, such as 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min, 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min, 200 r / min, or any value therebetween; and a time of 1-5 h, such as 1 h, 2 h, 3 h, 4 h, 5 h, or any value therebetween.

[0037] In the present application, in step S2, the stirring and reaction temperature is preferably 70-90 DEG C, and can be specifically 70 DEG C, 72 DEG C, 74 DEG C, 76 DEG C, 78 DEG C, 80 DEG C, 82 DEG C, 84 DEG C, 86 DEG C, 88 DEG C, 90 DEG C, or any value therebetween; the stirring and reaction rotation speed is preferably 100-200 r / min, and can be specifically 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min, 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min, 200 r / min, or any value therebetween; and the stirring and reaction time is preferably 1-5 h, and can be specifically 1 h, 2 h, 3 h, 4 h, 5 h, or any value therebetween.

[0038] In the present application, in step S3, the mixing conditions preferably include a temperature of 70-90℃, specifically 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃ or any value therebetween; a stirring speed of 100-200r / min, specifically 100r / min, 110r / min, 120r / min, 130r / min, 140r / min, 150r / min, 160r / min, 170r / min, 180r / min, 190r / min, 200r / min or any value therebetween; and a time of 30min-2h, specifically 30min, 40min, 50min, 60min, 80min, 100min, 120min or any value therebetween.

[0039] The present application also provides the use of the acrylate-modified polyurethane hot melt adhesive in electronic product bonding.

[0040] The acrylate-modified polyurethane hot melt adhesive provided by the present application is used for bonding substrates with conductivity.

[0041] The present application will be described in detail below through examples. The examples are intended to explain the present application and cannot be understood as limiting the present application. If a specific technique or condition is not specified in the examples, the technique or condition described in the literature in the art or according to the product manual is used. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained by market purchase.

[0042] Example 1

[0043] By weight, 15.96 g (5.320 mmol) of liquid polyether diol with number average molecular weight 3000 (Dow Voranol WD2130; Tg <0°C; melting point <25°C), 31.92 g (15.960 mmol) of liquid polyester diol with number average molecular weight 2000 (stepan pol PH-56; Tg = -15°C; melting point <25°C), 6.00 g of 1-ethyl-3-methylimidazolium tetrafluoroborate (melting point = 15°C), 4.5 g of fumed silica HDK H18, 0.3 g of 3- aminopropyltrimethoxysilane, and 0.4 g of water absorption agent Additive OF were heated to 110°C, vacuum dehydrated for 2 h under the condition of stirring at 150 r / min, then cooled to 80°C, 18.62 g (74.48 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.3 g of dibutyl tin dilaurate were added, and reacted for 2 h under the condition of stirring at 150 r / min, then 2.0 g of photoinitiator ITX, 10.0 g of 1,6-hexanediol diacrylate, and 10.0 g of trimethylolpropane formaldehyde acrylate were added, mixed for 1 h under the condition of stirring at 150 r / min, and then discharged to obtain an acrylate-modified polyurethane hot melt adhesive, which was stored in a vacuum-sealed and light-protected manner.

[0044] Example 2

[0045] By weight, 24.89 g (7.111 mmol) of liquid polyester diol with number average molecular weight 3500 (Dynacoll 7230; Tg = -30°C; melting point <25°C), 14.22 g (7.111 mmol) of liquid polyether diol with number average molecular weight 2000 (Dow Voranol 2120; Tg <0°C; melting point <25°C), 10.00 g of 1-butyl-3-methylimidazolium tetrafluoroborate (melting point = -71°C), 6.5 g of fumed silica TS-610, 0.7 g of 3-mercaptopropyltrimethoxysilane, and 1.2 g of water absorption agent Additive TI were heated to 110°C, vacuum dehydrated for 2 h under the condition of stirring at 150 r / min, then cooled to 80°C, 8.89 g (35.56 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.6 g of stannous octoate were added, and reacted for 2 h under the condition of stirring at 150 r / min, then 3.0 g of photoinitiator 369, 15.0 g of triethylene glycol diacrylate, and 15.0 g of tetrahydrofurfuryl acrylate were added, mixed for 1 h under the condition of stirring at 150 r / min, and then discharged to obtain an acrylate-modified polyurethane hot melt adhesive, which was stored in a vacuum-sealed and light-protected manner.

[0046] Example 3

[0047] By weight, 42.10 g (14.032 mmol) of liquid polycarbonate diol with a number average molecular weight of 3000 (Kuraray polyol C3090; Tg = -42°C; melting point < 25°C), 14.03 g (14.032 mmol) of liquid polyether diol with a number average molecular weight of 1000 (Dow Voranol 220-110; Tg < 0°C; melting point < 25°C), 4.00 g of hexyltriethylammonium bis(trifluoromethanesulfonyl)imide salt (melting point = 20°C), 2.5 g of fumed silica AEROSIL R202, 0.5 g of 3-glycidoxypropyltrimethoxysilane, and 1.0 g of water absorption agent Additive TI were heated to 110°C, vacuum dehydrated for 2 h under stirring at 150 r / min, then cooled to 80°C, 23.57 g (140.317 mmol) of hexamethylene diisocyanate (HDI) and 1.2 g of zinc isooctoate were added, and reacted for 2 h under stirring at 150 r / min, then 1.1 g of photoinitiator 819, 5.0 g of triethylene glycol diacrylate, and 5.0 g of dodecyl acrylate were added, mixed for 1 h under stirring at 150 r / min, and then discharged to obtain an acrylate-modified polyurethane hot melt adhesive, which was stored in a vacuum-sealed container in the dark.

[0048] Example 4

[0049] By weight, 29.82 g (14.908 mmol) of liquid polyester diol with a number average molecular weight of 2000 (Stepan pol PH-56; Tg = -15°C; melting point < 25°C), 14.91 g (14.908 mmol) of liquid polycarbonate diol with a number average molecular weight of 1000 (Kuraray polyol C1050; Tg < 0°C; melting point < 25°C), 13.00 g of N-butyl-N-methylpyrrolidine bisfluorosulfonyl imide salt (melting point = -15°C), 3.5 g of fumed silica AEROSIL R972, 1.5 g of 3-isocyanate propyl trimethoxysilane, and 0.8 g of water absorption agent Additive TI were heated to 110°C, vacuum dehydrated for 2 h under stirring at 150 r / min, then cooled to 80°C, 26.48 g (119.263 mmol) of isophorone diisocyanate (IPDI) and 1.5 g of bismuth isooctoate were added, and reacted for 2 h under stirring at 150 r / min, then 0.5 g of photoinitiator TPO, 4.0 g of neopentyl glycol diacrylate, and 4.0 g of isooctyl acrylate were added, mixed for 1 h under stirring at 150 r / min, and then discharged to obtain an acrylate-modified polyurethane hot melt adhesive, which was stored in a vacuum-sealed container in the dark.

[0050] Example 5

[0051] By weight, 28.95 g (8.272 mmol) of liquid polyester diol with number average molecular weight 3500 (Dynacoll 7210; Tg = -15°C; melting point < 25°C), 16.54 g (16.544 mmol) of liquid polycarbonate diol with number average molecular weight 1000 (PLACCEL 210N; Tg = -17°C; melting point = 32-37°C), 8.00 g of 1,3-diethylimidazolium bis(trifluoromethanesulfonyl)imide salt (melting point = 12.4°C), 4.0 g of fumed silica HDK H20, 1.7 g of 3-acryloxypropyltrimethoxysilane, and 0.5 g of water absorbent Additive TI, were heated to 110°C, vacuum dehydrated for 2 h under stirring at 150 r / min, then cooled to 80°C, 19.50 g (74.446 mmol) of dicyclohexylmethane-4,4'-diisocyanate (HMDI) and 1.3 g of stannous octoate were added, and reacted for 2 h under stirring at 150 r / min, then 1.5 g of photoinitiator 184, 10.0 g of diethylene glycol diacrylate, and 8.0 g of tridecyl acrylate were added, mixed for 1 h under stirring at 150 r / min, and discharged to obtain an acrylate-modified polyurethane hot melt adhesive, which was stored in a vacuum-sealed container in the dark.

[0052] Comparative Example 1

[0053] By weight, 39.41 g (13.137 mmol) of liquid polycarbonate diol with number average molecular weight 3000 (Kuraray polyol C3090; Tg = -42°C; melting point < 25°C), 8.76 g (4.379 mmol) of liquid polyether diol with number average molecular weight 2000 (Dow Voranol 2120; Tg < 0°C; melting point < 25°C), 4.38 g (4.379 mmol) of liquid polyether diol with number average molecular weight 1000 (Dow Voranol 220-110; Tg < 0°C; melting point < 25°C), 5.5 g of fumed silica HDK H17, 0.3 g of 3- aminopropyltrimethoxysilane, and 0.5 g of water absorbent Additive OF, were heated to 110°C, vacuum dehydrated for 2 h under stirring at 150 r / min, then cooled to 80°C, 41.05 g (164.211 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.1 g of dibutyltin dilaurate were added, and reacted for 2 h under stirring at 150 r / min, and discharged to obtain a reference polyurethane hot melt adhesive, which was stored in a vacuum-sealed container.

[0054] Comparative Example 2

[0055] By weight, 42.11 g (12.031 mmol) of polyester diol with number average molecular weight of 3500 (Yingchuang Dynacoll 7380; melting point = 70°C), 24.06 g (12.031 mmol) of liquid polyether diol with number average molecular weight of 2000 (Dow Voranol 2120; Tg < 0°C; melting point < 25°C), 10.0 g of thermoplastic acrylic resin BM751 (Tg = 49°C), 5.0 g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (melting point = -12°C), 5.0 g of propylene carbonate, 1.0 g of 3-mercaptopropyltrimethoxysilane, and 0.5 g of water absorption agent Additive OF were heated to 110°C, vacuum dehydrated for 2 h under the condition of stirring at 150 r / min, then cooled to 80°C, 12.03 g (48.123 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.3 g of stannous octoate were added, and the product was discharged after reaction for 2 h under the condition of stirring at 150 r / min to obtain a reference polyurethane hot melt adhesive, which was stored in vacuum sealing.

[0056] Comparative Example 3

[0057] The polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the liquid polyether diol and the liquid polyester diol were replaced by solid polyester diol and solid polycarbonate diol with the same molar amount and a melting point higher than 40°C, and the other conditions were the same as in Example 1, as follows:

[0058] By weight, 15.96 g (5.320 mmol) of solid polyester diol with number average molecular weight of 3000 (Hoopol F-580; melting point = 50°C), 31.92 g (15.960 mmol) of solid polycarbonate diol with number average molecular weight of 2000 (UH-CARB200; melting point = 50°C), 6.00 g of 1-ethyl-3-methylimidazolium tetrafluoroborate (melting point = 15°C), 4.5 g of fumed silica HDK H18, 0.3 g of 3-aminopropyltrimethoxysilane, and 0.4 g of water absorption agent Additive OF were heated to 110°C, vacuum dehydrated for 2 h under the condition of stirring at 150 r / min, then cooled to 80°C, 18.62 g (74.48 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.3 g of dibutyltin dilaurate were added, and the product was discharged after reaction for 2 h under the condition of stirring at 150 r / min, to obtain a reference polyurethane hot melt adhesive, which was stored in vacuum sealing and away from light.

[0059] Comparative Example 4

[0060] The polyurethane hot-melt adhesive was prepared according to the method of Example 1, except that the polyisocyanate compound was adjusted so that the molar equivalent ratio of isocyanate groups in the polyisocyanate compound of Example 1 to hydroxyl groups in the low-viscosity polyol compound was lowered from 3.5:1 to 1.8:1, at which point the polyurethane prepolymer could not be double-end capped with isocyanate, as follows:

[0061] By weight, 18.47 g (6.157 mmol) of liquid polyether diol (Dow Voranol WD2130; Tg <0°C; melting point <25°C) with a number average molecular weight of 3000, 36.94 g (18.472 mmol) of liquid polyester diol (stepanpol PH-56; Tg = -15°C; melting point <25°C) with a number average molecular weight of 2000, 6.00 g of 1-ethyl-3-methylimidazolium tetrafluoroborate (melting point = 15°C), 4.5 g of fumed silica HDK H18, 0.3 g of 3-aminopropyltrimethoxysilane, and 0.4 g of water absorption additive Additive OF were heated to 110°C, vacuum dehydrated for 2 h under stirring at 150 r / min, then cooled to 80°C, 11.08 g (44.333 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.3 g of dibutyltin dilaurate were added, and reacted for 2 h under stirring at 150 r / min, then 2.0 g of photoinitiator ITX, 10.0 g of 1,6-hexanediol diacrylate, and 10.0 g of trimethylolpropane formaldehyde acrylate were added, mixed for 1 h under stirring at 150 r / min, and then discharged to obtain the reference polyurethane hot-melt adhesive, which was stored in a vacuum-sealed container in the dark.

[0062] Comparative Example 5

[0063] The polyurethane hot-melt adhesive was prepared according to the method of Example 1, except that no ionic liquid was added, and the other conditions were the same as in Example 1, as follows:

[0064] By weight, 15.96 g (5.320 mmol) of liquid polyether diol with number average molecular weight 3000 (Dow Voranol WD2130; Tg <0°C; melting point <25°C), 31.92 g (15.960 mmol) of liquid polyester diol with number average molecular weight 2000 (Stepanpol PH-56; Tg = -15°C; melting point <25°C), 4.5 g of fumed silica HDK H18, 0.3 g of 3- aminopropyltrimethoxysilane and 0.4 g of water absorbent Additive OF were heated to 110°C, vacuum dehydrated for 2 h under stirring at 150 r / min, then cooled to 80°C, 18.62 g (74.48 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.3 g of dibutyltin dilaurate were added, reacted for 2 h under stirring at 150 r / min, then 2.0 g of photoinitiator ITX, 10.0 g of 1,6-hexanediol diacrylate and 10.0 g of trimethylolpropane formal acrylate were added, mixed for 1 h under stirring at 150 r / min, and then discharged to obtain a reference polyurethane hot melt adhesive, which was vacuum sealed and stored in the dark.

[0065] Comparative Example 6

[0066] A polyurethane hot melt adhesive was prepared according to the method of Example 1, except that 1,6-hexanediol diacrylate and trimethylolpropane formal acrylate were not added, and the other conditions were the same as in Example 1, as follows:

[0067] By weight, 15.96 g (5.320 mmol) of liquid polyether diol with number average molecular weight 3000 (Dow Voranol WD2130; Tg <0°C; melting point <25°C), 31.92 g (15.960 mmol) of liquid polyester diol with number average molecular weight 2000 (Stepanpol PH-56; Tg = -15°C; melting point <25°C), 6.00 g of 1-ethyl-3-methylimidazolium tetrafluoroborate (melting point = 15°C), 4.5 g of fumed silica HDK H18, 0.3 g of 3- aminopropyltrimethoxysilane and 0.4 g of water absorbent Additive OF were heated to 110°C, vacuum dehydrated for 2 h under stirring at 150 r / min, then cooled to 80°C, 18.62 g (74.48 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.3 g of dibutyltin dilaurate were added, reacted for 2 h under stirring at 150 r / min, then 2.0 g of photoinitiator ITX was added, mixed for 1 h under stirring at 150 r / min, and then discharged to obtain a reference polyurethane hot melt adhesive, which was vacuum sealed and stored in the dark.

[0068] Comparative Example 7

[0069] The polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the amount of 1,6-hexanediol diacrylate and trimethylolpropane formal acrylate added was increased to 40.0 g. Otherwise, it was the same as in Example 1, as detailed below:

[0070] By weight, 15.96 g (5.320 mmol) of liquid polyether diol with a number-average molecular weight of 3000 (Dow Voranol WD2130; Tg < 0℃; melting point < 25℃), 31.92 g (15.960 mmol) of liquid polyester diol with a number-average molecular weight of 2000 (Stepanpol PH-56; Tg = -15℃; melting point < 25℃), 6.00 g of 1-ethyl-3-methylimidazolium tetrafluoroborate (melting point = 15℃), 4.5 g of fumed silica HDK H18, and 0.3 g of... 3-Aminopropyltrimethoxysilane and 0.4 g of water-absorbing agent AdditiveOF were heated to 110 °C and vacuum dehydrated for 2 h under stirring at 150 r / min. Then, the mixture was cooled to 80 °C, and 18.62 g (74.48 mmol) of diphenylmethane-4,4'-diisocyanate (MDI) and 0.3 g of dibutyltin dilaurate were added. The mixture was stirred at 150 r / min for 2 h. Then, 2.0 g of photoinitiator ITX, 40.0 g of 1,6-hexanediol diacrylate and 40.0 g of trimethylolpropane formal acrylate were added. The mixture was stirred at 150 r / min for 1 h and then discharged to obtain the reference polyurethane hot melt adhesive, which was vacuum sealed and stored in the dark.

[0071] Test case

[0072] The samples from the examples and comparative examples were compared and tested using the following method:

[0073] (1) Viscosity at 25℃: Samples of polyurethane hot melt adhesives obtained from the above examples and comparative examples were taken into a cone-plate viscometer and the viscosity of the adhesives at 25℃ and 1 rpm was tested using the cone-plate viscometer. The results are shown in Table 1.

[0074] (2) Bond strength at different curing times: The polyurethane hot melt adhesives obtained in the above embodiments and comparative examples were applied at room temperature using a dispensing machine (if solid at room temperature, the dispensing temperature was set to 110℃). A rectangular adhesive line of 25mm × 4mm was applied to a stainless steel substrate, and then the adhesive was irradiated with a 365nm UV-LED light source at 2000mJ / cm². 2After the irradiation, another stainless steel substrate was attached to the stainless steel substrate, and after the attachment, the sample was cured at 25°C and 50% RH for 5 min, 30 min, and 48 h. Then, the prepared adhesive sample was run at a speed of 10 mm / min in the shearing direction until the adhesive sample failed, and the maximum force value displayed by the instrument was recorded. The shearing adhesive strength of the polyurethane hot melt adhesive to the stainless steel substrate before energization was calculated in combination with the adhesive area. The results are shown in Table 1.

[0075] (3) Adhesive strength after energization: The polyurethane hot melt adhesive obtained in each of the above examples and comparative examples was dispensed at room temperature using a dispensing machine (if it was solid at room temperature, the dispensing temperature was set to 110°C), a 25 mm x 4 mm rectangular glue line was coated on a stainless steel substrate, and then the glue was irradiated with a 365 nm UV-LED light source at an energy of 2000 mJ / cm 2 After the irradiation, another stainless steel substrate was attached to the stainless steel substrate, and after the attachment, the sample was cured at 25°C and 50% RH for 48 h. Then, the positive and negative leads of the direct current power supply were clamped at both ends of the shearing sample, a certain voltage was applied for a certain time, and after the energization, the shearing sample was removed. The prepared adhesive sample was run at a speed of 10 mm / min in the shearing direction until the adhesive sample failed, and the maximum force value displayed by the instrument was recorded. The shearing adhesive strength of the polyurethane hot melt adhesive to the stainless steel substrate after energization was calculated in combination with the adhesive area. The results are shown in Table 1.

[0076] Table 1

[0077]

[0078] As can be seen from the results in Table 1, the acrylate modified polyurethane hot melt adhesive provided by the present application has a lower viscosity at room temperature, can be directly dispensing at room temperature, significantly improves the defect that the reactive polyurethane hot melt adhesive needs to be applied with heating, increases the convenience of the use of the adhesive, and reduces the risk of being scalded in the process of using the heating equipment by the operator. According to practical experience, the adhesive has a detachable property when the bonding strength at room temperature is 2.0 MPa or less, and otherwise does not have the detachable property. As can be seen from the results in Table 1, the acrylate modified polyurethane hot melt adhesive provided by the present application can quickly establish a high initial bonding strength after UV irradiation, has the function of realizing preliminary positioning in a short time, has excellent final bonding strength after complete curing, and the bonding strength of the adhesive can obviously decay after power-on, and even can directly fall off, and has excellent power-on detachable performance. In summary, the acrylate modified polyurethane hot melt adhesive provided by the present application has a low melt viscosity, can be dispensing at room temperature, has high initial bonding strength and final bonding strength, has a fast curing speed, and at the same time has the detachable function under the condition of power-on, and has a broad practical application prospect.

[0079] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above embodiments without departing from the principles and purposes of the present application within the scope of the present application.

Claims

1. An acrylate-modified polyurethane adhesive, characterized in that, The acrylate-modified polyurethane adhesive has a viscosity range of 1000~150000cps at 25°C and a bond strength attenuation rate of over 80% after being energized with a voltage of 1~100V. The acrylate-modified polyurethane adhesive contains a polyurethane prepolymer mixture, acrylate compounds, ionic liquids, and photoinitiators. Both ends of the prepolymer in the polyurethane prepolymer mixture are isocyanate-terminated. The polyol structural units in the polyurethane prepolymer mixture are derived from low-viscosity polyol compounds with a glass transition temperature below 0°C and a melting point below 40°C. The mass ratio of the polyurethane prepolymer mixture to the acrylate compound is (1.5~9):

1. The raw materials for preparing the acrylate-modified polyurethane adhesive contain polyisocyanates, low-viscosity polyol compounds, acrylate compounds, ionic liquids, photoinitiators, and optionally rheology modifiers and silane coupling agents. The water-absorbing agent and catalyst, wherein the molar equivalent ratio of the isocyanate group in the polyisocyanate compound to the hydroxyl group in the low-viscosity polyol compound is (2.5~5):1; the acrylate compound is selected from at least one of octadecyl acrylate, tetrahydrofuran acrylate, dodecyl acrylate, 2-phenoxyethyl acrylate, isodecanyl acrylate, isooctyl acrylate, tridecyl acrylate, trimethylolpropane formal acrylate, methoxy polyethylene glycol monoacrylate, alkyltetrahydrofuran acrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate.

2. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, Based on the total weight of the raw materials for preparing the acrylate-modified polyurethane adhesive, the total content of the polyisocyanate compound and the low-viscosity polyol compound is 45-80%, the content of the acrylate compound is 5-35%, the content of the ionic liquid is 2-15%, the content of the photoinitiator is 0.1-5%, the content of the rheology modifier is 2-10%, the content of the silane coupling agent is 0.1-3%, the content of the water absorbent is 0.1-2%, and the content of the catalyst is 0.1-2%.

3. The acrylate-modified polyurethane adhesive according to claim 1, 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.

4. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, The number average molecular weight of the low-viscosity polyol compound is 400~6000 g / mol; the low-viscosity polyol compound is selected from at least one of liquid polyester polyol, liquid polyether polyol, liquid polycarbonate polyol, fatty acid dimer diol, castor oil derivative polyol and hydroxyl-terminated polybutadiene polyol.

5. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, The melting point of the ionic liquid is below 25°C.

6. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, The ionic liquid is composed of organic cations and anions. The organic cations are selected from at least one of imidazole cations, pyrrole cations, quaternary ammonium salt cations, quaternary phosphate salt cations, pyrrolidine cations, and piperidine cations. The anions are selected from at least one of trifluoromethanesulfonate anion, tetrafluoroborate anion, hexafluorophosphate anion, difluoromethanesulfonylimide anion, hydrogen sulfate anion, ethyl sulfate anion, and p-toluenesulfonate anion.

7. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, The ionic liquid is selected from 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-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-2,3-dimethylimidazolium ethyl sulfate, and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. At least one of the following: 1,3-diethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1,2-dimethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium 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.

8. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, The photoinitiator is selected from at least one of benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, dicocene compounds, oxime ester compounds, benzoin ether compounds, and thioxanone.

9. The acrylate-modified polyurethane 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.

10. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, The rheology modifier is fumed silica.

11. The acrylate-modified polyurethane adhesive according to claim 1, 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-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyl At least one of the following: methyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 3-isocyanate propyltrimethoxysilane.

12. The acrylate-modified polyurethane adhesive according to claim 1, characterized in that, The desiccant is selected from at least one of molecular sieve desiccant, oxazolidine desiccant, p-methylbenzenesulfonyl isocyanate, and triethyl orthoformate.

13. A method for preparing the acrylate-modified polyurethane adhesive according to any one of claims 1 to 12, characterized in that, The method includes the following steps: S1. The low-viscosity polyol compound and ionic liquid, along with optional rheology modifiers, silane coupling agents and dehydrating agents, are dehydrated to obtain a pretreated product. S2. The pretreated product, polyisocyanate compound and optional catalyst are stirred and reacted at 70~90℃ for 1~5h to obtain a prepolymer containing a polyurethane prepolymer mixture. S3. Mix the prepolymer with the acrylate compound and the photoinitiator evenly to obtain the acrylate-modified polyurethane adhesive.

14. The application of the acrylate-modified polyurethane adhesive according to any one of claims 1 to 12 in the bonding of electronic products.

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