An acrylate-modified polyurethane hot melt adhesive with excellent bonding performance and electrical disassembly, as well as its preparation method and application

Abstract

The present invention belongs to the technical field of polyurethane hot melt adhesives, and specifically relates to an acrylate-modified polyurethane hot melt adhesive with excellent bonding properties and electrical disassembly, as well as its preparation method and application. The raw materials for preparing the acrylate-modified polyurethane hot melt adhesive contain an acrylate monomer, an alkali metal salt, a polyol compound, a polyisocyanate compound, a photoinitiator, and optionally a silane coupling agent, a catalyst, and a water absorbent; the mass ratio of the acrylate monomer to the alkali metal salt is (1 to 10):1; the mass ratio of the acrylate monomer to the polyol compound and the polyisocyanate compound is 1:(1.3 to 6.4):(0.15 to 2.3). The present invention introduces a specific ratio of UV-curable acrylate monomer and alkali metal salt, and regulates the ratio of the acrylate monomer to the polyol compound and the polyisocyanate compound, thereby obtaining an acrylate-modified polyurethane hot melt adhesive with excellent bonding properties and electrical disassembly properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethane hot melt adhesives, and in particular relates to an acrylate-modified polyurethane hot melt adhesive with excellent bonding performance and electrical disassembly, as well as a preparation method and application thereof. Background Art

[0002] Reactive polyurethane hot melt adhesives cure primarily through the reaction of isocyanates with moisture in the air to form a chemical cross-linking structure, resulting in high bond strength. They are widely used in electronic products such as smartphones, tablets, smartwatches, and TWS earphones. Because electronic components are often of high value, disassembly of bonded components is often necessary for assembly failures, product repairs, and the recycling of valuable electronic components. Therefore, adhesives are often required to provide both excellent bonding reliability and easy disassembly under certain conditions.

[0003] However, it is usually difficult to disassemble the fully cured polyurethane hot melt adhesive, because the covalent bond obtained by the reaction of isocyanate with moisture is irreversible, and the cross-linked structure is difficult to be destroyed. The commonly used methods of adhesive removal are usually achieved by means of high temperature, chemical reagents, external force and other means, which can easily cause greater damage to the adhesive substrate. In recent years, studies have shown that electrical adhesive removal is a relatively mild means, which mainly involves adding alkali metal salts and solvated matrices to the polyurethane hot melt adhesive to give the polyurethane hot melt adhesive the function of being disassembled under electrical conditions. However, although the existing electrically disassembleable polyurethane hot melt adhesive has the function of being disassembled under electrical conditions, it still has a large gap with the traditional widely used polyurethane hot melt adhesive in terms of bonding strength, curing speed, heat resistance and other properties. The electrically disassembled polyurethane hot melt adhesive developed by the existing technology is still difficult to meet the performance requirements of actual application scenarios.

[0004] Therefore, there is an urgent need to develop an adhesive that can be disassembled under power-on conditions while also having excellent bonding properties to meet the market demand for high-performance detachable adhesives. Summary of the Invention

[0005] The purpose of the present invention is to address the shortcomings of existing polyurethane hot melt adhesives that are difficult to achieve both electrical disassembly and excellent bonding performance, and to provide an acrylate-modified polyurethane hot melt adhesive with excellent bonding performance and electrical disassembly, as well as a preparation method and application thereof.

[0006] In a first aspect, the present invention provides an acrylate-modified polyurethane hot melt adhesive, wherein the raw materials for preparing the acrylate-modified polyurethane hot melt adhesive contain an acrylate monomer, an alkali metal salt, a polyol compound, a polyisocyanate compound, a photoinitiator, and optionally a silane coupling agent, a catalyst, and a water absorbent; the mass ratio of the acrylate monomer to the alkali metal salt is (1 to 10):1; the mass ratio of the acrylate monomer, the polyol compound, and the polyisocyanate compound is 1:(1.3 to 6.4):(0.15 to 2.3).

[0007] In some specific embodiments, the content of the acrylate monomer is 10 to 30 parts by weight, the content of the alkali metal salt is 3 to 15 parts by weight, the content of the polyol compound is 35 to 66 parts by weight, the content of the polyisocyanate compound is 5 to 25 parts by weight, the content of the photoinitiator is 0.5 to 5 parts by weight, the content of the silane coupling agent is 0 to 3 parts by weight, the content of the catalyst is 0 to 2 parts by weight, and the content of the water absorbent is 0 to 2 parts by weight.

[0008] In some specific embodiments, the viscosity of the acrylate monomer at 25° C. is 0.1 to 30 mPa.s.

[0009] In some specific embodiments, the acrylate monomer is selected from at least one of octadecyl acrylate, tetrahydrofuran acrylate, dodecyl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, isooctyl acrylate, tridecyl acrylate, trimethylolpropane formal 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 and dipropylene glycol diacrylate.

[0010] In some specific embodiments, the alkali metal salt is a compound composed of an alkali metal cation and at least one anion selected from the group consisting of an organic acid anion, an inorganic acid anion, and an organic sulfonyl imide anion.

[0011] In some specific embodiments, the alkali metal salt is selected from at least one of lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium chloride, lithium sulfate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroantimonate, lithium nitrate, sodium trifluoromethanesulfonate, sodium bistrifluoromethanesulfonyl imide, sodium chloride, sodium sulfate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroantimonate, sodium nitrate, potassium trifluoromethanesulfonate, potassium bistrifluoromethanesulfonyl imide, potassium chloride, potassium sulfate, potassium nitrate, potassium tetrafluoroborate, potassium hexafluorophosphate and potassium hexafluoroantimonate.

[0012] In some specific embodiments, the polyol compound is selected from at least one of polyester polyol, polyether polyol, polycarbonate polyol and polyalkylene polyol.

[0013] In some specific embodiments, the number average molecular weight of the polyol compound is 1000 to 4000 g / mol.

[0014] In some specific embodiments, 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 xylylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-pentane diisocyanate, 1,4-phenylene diisocyanate, m-xylylene diisocyanate, tetramethylxylylene diisocyanate, norbornane dimethylene isocyanate, lysine diisocyanate, triphenylmethane triisocyanate, thiophosphoric acid triphenyl isocyanate and 1,6,11-undecane triisocyanate.

[0015] In some specific embodiments, the photoinitiator is selected from at least one of benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, oxime ester compounds, benzoin ether compounds and thioxanthone.

[0016] In some specific embodiments, the silane coupling agent is selected from at least one of mercaptosilane, epoxysilane, aminosilane, alkenylsilane and isocyanatesilane.

[0017] In some specific embodiments, the catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine and 2,2-dimorpholinodiethyl ether.

[0018] In some specific embodiments, the water absorbent is selected from at least one of a molecular sieve desiccant, an oxazolidine desiccant, p-methylbenzenesulfonyl isocyanate, and triethyl orthoformate.

[0019] In a second aspect, the present invention provides a method for preparing the above-mentioned acrylate-modified polyurethane hot melt adhesive, which comprises uniformly mixing an acrylate monomer, an alkali metal salt, a polyol compound, a polyisocyanate compound, a photoinitiator, and an optional silane coupling agent, a catalyst, and a water absorbent to obtain an acrylate-modified polyurethane hot melt adhesive.

[0020] In a third aspect, the present invention also provides the use of the above-mentioned acrylate-modified polyurethane hot melt adhesive in bonding electronic products.

[0021] Existing electrically dismantling polyurethane hot-melt adhesives typically incorporate an alkali metal salt and a solvated matrix to form a liquid electrolyte, thereby imparting electrical dismantling properties. However, since the liquid electrolyte cannot undergo a curing reaction during the adhesive curing process, it remains in the adhesive system as a "plasticizer" after curing. This "plasticizer" affects the internal structure of the cured colloid, negatively affecting the adhesive's bond strength and causing a significant decrease in bond strength. Therefore, solving the problem of "plasticizers" in the cured colloid is key to improving the adhesive performance of electrically dismantling polyurethane hot-melt adhesives.

[0022] The key to the present invention is to introduce a specific ratio of UV-curable acrylate monomers and alkali metal salts. On the one hand, the introduced acrylate monomers make the alkali metal salts uniformly dissolve and disperse in the polyurethane hot melt colloid, giving it the property of being electrically disassembled under power conditions. On the other hand, under the action of a photoinitiator, the acrylate monomers can undergo a curing reaction. Compared with the difficult-to-curing solvated matrix commonly used in the prior art, the negative impact of the "plasticizer" formed by the uncured solvated matrix on the bonding performance of the polyurethane hot melt adhesive can be solved. In addition, the ionic conductivity of the acrylate monomer decreases less after curing than when it is not cured, and has little effect on the ion migration ability of the cured system. It is speculated that this may be because in addition to being affected by the action of the solvated matrix, the ion migration is also affected by the dissociated ions and polymers. The dipole interaction between the polymer chain segments is related to the dipole interaction between the polymer chain segments. The movement of the polymer chain segments can help the migration of ions. Therefore, the acrylate monomer can still maintain good electrically disassembly performance after curing. At the same time, the ratio of the acrylate monomer to the polyol compound and the polyisocyanate compound is also regulated, so that the acrylate-modified polyurethane hot melt adhesive can quickly establish initial bonding strength after UV curing, while also being able to maintain a certain open time. The UV light curing and moisture curing reaction processes occurring in the system can play a good role in mutual cooperation, which is not only conducive to improving the initial bonding strength, but also provides the possibility for the UV and moisture dual-curing acrylate-modified polyurethane hot melt adhesive to be used for bonding opaque conductive metal substrates, significantly improving the defect of poor bonding performance of existing electrical disassembly adhesives.

[0023] In summary, the present invention introduces a specific ratio of acrylate monomer and alkali metal salt, and on this basis adjusts the ratio of acrylate monomer to polyol compound and polyisocyanate compound. The acrylate-modified polyurethane hot melt adhesive prepared in this way has excellent bonding properties and electrical disassembly properties, and has broad practical application prospects. DETAILED DESCRIPTION

[0024] The raw materials for preparing the acrylate-modified polyurethane hot-melt adhesive provided by the present invention include an acrylate monomer, an alkali metal salt, a polyol compound, a polyisocyanate compound, a photoinitiator, and optionally a silane coupling agent, a catalyst, and a water absorbent. The mass ratio of the acrylate monomer to the alkali metal salt is (1-10):1, such as 1:1, 2:1, 5:1, 8:1, 10:1, or any value therebetween. The mass ratio of the acrylate monomer to the polyol compound is 1:(1.3-6.4), such as 1:1.3, 1:1.5, 1:1.8, 1:2, 1:3, 1:4, 1:5, 1:6, 1:6.4, or any value therebetween. The mass ratio of the acrylate monomer to the polyisocyanate compound is 1:(0.15-2.3), such as 1:0.15, 1:0.18, 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.3 or any value therebetween. When the content of the acrylate monomer is too high, the speed of the acrylate curing reaction is relatively fast after UV irradiation, and the degree of curing is relatively high, which greatly reduces the adhesion of the colloid surface, thereby reducing the adhesion between the interface of the acrylate-modified polyurethane hot melt adhesive and the bonded substrate, and further reducing the bonding strength after the final curing is completed. Therefore, in addition to controlling the mass ratio of the acrylate monomer to the alkali metal salt so that the acrylate-modified polyurethane hot melt adhesive has good electrical conductivity, it is also necessary to regulate the mass ratio of the acrylate monomer to the polyol compound and the polyisocyanate compound, and the components cooperate with each other, so as to simultaneously improve the curing speed and bonding strength of the acrylate-modified polyurethane hot melt adhesive.

[0025] In the present invention, the content of the acrylate monomer is preferably 10 to 30 parts by weight, such as 10, 12, 15, 18, 20, 22, 25, 28, 30 parts by weight or any value therebetween; the content of the alkali metal salt is preferably 3 to 15 parts by weight, such as 3, 5, 7, 10, 12, 15 parts by weight or any value therebetween; the content of the polyol compound is preferably 35 to 66 parts by weight, such as 35, 38, 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 66 parts by weight or any value therebetween; the content of the polyisocyanate compound is preferably 5 to 25 parts by weight, such as 5, 8, 10, 12, 15, 18, 20, 22, 25 parts by weight or any value therebetween the content of the photoinitiator is preferably 0.5 to 5 parts by weight, such as 0.5, 1, 2, 3, 4, 5 parts by weight or any value therebetween; the content of the silane coupling agent is preferably 0 to 3 parts by weight, such as 0, 0.1, 0.2, 0.5, 0.8, 1, 1.5, 2, 2.5, 3 parts by weight or any value therebetween; the content of the catalyst is preferably 0 to 2 parts by weight, such as 0, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2 parts by weight or any value therebetween; the content of the water absorbent is preferably 0 to 2 parts by weight, such as 0, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2 parts by weight or any value therebetween.

[0026] In the present invention, the type of the acrylate is not specifically limited, as long as it is a compound containing at least one photocurable acrylate group. Specific examples include, but are not limited to, at least one of octadecyl acrylate, tetrahydrofuran acrylate, dodecyl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, isooctyl acrylate, tridecyl acrylate, trimethylolpropane formal 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 and dipropylene glycol diacrylate. The viscosity of the acrylate monomer at 25°C is preferably 0.1 to 30 mPa.s, such as 0.1 mPa.s, 0.5 mPa.s, 1 mPa.s, 5 mPa.s, 10 mPa.s, 15 mPa.s, 20 mPa.s, 25 mPa.s, 30 mPa.s, or any value therebetween. When the viscosity of the acrylate monomer is within this preferred range, the alkali metal salt is more easily dispersed within the polyurethane hot melt adhesive system, thereby imparting good electrical disassembly properties to the system.

[0027] In the present invention, the alkali metal salt can be a compound composed of an alkali metal cation and at least one anion selected from organic acid anions, inorganic acid anions, and organic sulfonyl imide anions, preferably a fluorine-containing alkali metal lithium salt. The inventors of the present invention have found that when the alkali metal salt is preferably a fluorine-containing alkali metal lithium salt, it can impart better electrical disassembly performance to the polyurethane hot melt adhesive. Specifically, the alkali metal cation of the alkali metal salt can be at least one of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), preferably at least one of lithium (Li), sodium (Na), and potassium (K). The anion of the alkali metal salt can be at least one of trifluoromethanesulfonate ion, carboxylate ion, sulfinate ion, chloride ion, sulfate ion, sulfite ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroantimonate ion, nitrate ion, and bistrifluoromethanesulfonyl imide ion, preferably trifluoromethanesulfonate ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroantimonate ion, and bistrifluoromethanesulfonyl imide ion. Specific examples of the alkali metal salt include, but are not limited to, at least one of lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium chloride, lithium sulfate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroantimonate, lithium nitrate, sodium trifluoromethanesulfonate, sodium bistrifluoromethanesulfonyl imide, sodium chloride, sodium sulfate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroantimonate, sodium nitrate, potassium trifluoromethanesulfonate, potassium bistrifluoromethanesulfonyl imide, potassium chloride, potassium sulfate, potassium nitrate, potassium tetrafluoroborate, potassium hexafluorophosphate, and potassium hexafluoroantimonate. The alkali metal salt is more preferably selected from at least one of lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium hexafluoroantimonate.

[0028] In the present invention, the polyol compound is preferably at least one selected from polyester polyols, polyether polyols, polycarbonate polyols, and polyalkylene polyols. The number average molecular weight (Mn) of the polyol compound is preferably 1000 to 4000 g / mol, such as 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, or any value therebetween. Specifically, the type and source of the polyester polyol are not particularly limited, and may be any existing commercially available polyester polyol, or a polyester polyol obtained by the reaction between a polycarboxylic acid and a polyol, or a poly-ε-caprolactone polyol obtained by ring-opening polymerization of ε-caprolactone. The polycarboxylic acid is preferably at least one of terephthalic acid, isophthalic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decamethylene dicarboxylic acid, and dodecamethylene dicarboxylic acid. The polyol is preferably at least one of ethylene glycol, propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, and cyclohexanediol. The type and source of the polyether polyol are not particularly limited, and may be various existing commercially available polyether polyols, or may be at least one of ring-opening polymers, random copolymers, block copolymers, and bisphenol-type polyoxyalkylene modified products of ethylene glycol, propylene glycol, tetrahydrofuran, and 3-methyltetrahydrofuran. The bisphenol-type polyoxyalkylene modified product is a polyether polyol obtained by adding alkylene oxide to the active hydrogen portion of the bisphenol-type molecular skeleton, and can be a random copolymer or a block copolymer. The alkylene oxide can be at least one of ethylene oxide, propylene oxide, butylene oxide, and isobutylene oxide. The type and source of the polycarbonate polyol are not particularly limited, and specific examples include, but are not limited to, at least one of polycarbonate 1,6-hexanediol, polycarbonate-1,4-butanediol-1,6-hexanediol, polycarbonate-1,5-pentanediol-1,6-hexanediol, polycarbonate-caprolactone hexanediol, polycarbonate-1,4-cyclohexanedimethanol-1,6-hexanediol, polyethylene carbonate, polypropylene carbonate, polybutylene carbonate, and polycarbonate-1,6-hexanediol. There is no particular limitation on the type and source of the polyalkylene polyol, and specific examples thereof include, but are not limited to, at least one of polybutadiene polyol, hydrogenated polybutadiene polyol, and hydrogenated polyisoprene polyol.

[0029] In the present invention, the type and source of the polyisocyanate compound are not particularly limited, as long as it is a class of compounds containing two or more isocyanate groups. Specific examples 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-pentamethylene diisocyanate, 1,4-phenylene diisocyanate, m-xylylene diisocyanate, tetramethylxylylene diisocyanate, norbornane dimethylene isocyanate, lysine diisocyanate, triphenylmethane triisocyanate, thiophosphoric acid triphenyl isocyanate, and 1,6,11-undecane triisocyanate.

[0030] In the present invention, the type and source of the photoinitiator are not particularly limited, as long as it is a compound that can initiate a curing reaction of the acrylate monomer under UV light. It can be a conventional choice in the field, preferably at least one selected from 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 invention, the type and source of the silane coupling agent are not particularly limited, and is preferably at least one selected from mercaptosilane, epoxysilane, aminosilane, alkenylsilane and isocyanate silane, and specific examples thereof include but are not limited to: 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, At least one of 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 3-isocyanatepropyltrimethoxysilane.

[0032] In the present invention, the type and source of the catalyst are not particularly limited and can be conventionally selected in the art. Specific examples include, but are not limited to, at least one of dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine, and 2,2-dimorpholinodiethyl ether.

[0033] In the present invention, the type and source of the water absorbent are not particularly limited and can be conventionally selected in the art. Specific examples include, but are not limited to, at least one of molecular sieve desiccant, oxazolidine desiccant, p-toluenesulfonyl isocyanate, and triethyl orthoformate.

[0034] The preparation method of the acrylate-modified polyurethane hot melt adhesive provided by the present invention comprises uniformly mixing an acrylate monomer, an alkali metal salt, a polyol compound, a polyisocyanate compound, a photoinitiator, and optionally a silane coupling agent, a catalyst, and a water absorbent to obtain the acrylate-modified polyurethane hot melt adhesive. The present invention does not particularly limit the mixing method. In a preferred embodiment, the mixing method specifically comprises the following steps: S1. subjecting the acrylate monomer, the alkali metal salt, the polyol compound, the polyisocyanate compound, and optionally a catalyst, and a water absorbent to a first mixing process to obtain an acrylate-modified polyurethane prepolymer mixture; S2. subjecting the acrylate-modified polyurethane prepolymer to a second mixing process with the photoinitiator and optionally a silane coupling agent to obtain the acrylate-modified polyurethane hot melt adhesive.

[0035] In the above-mentioned method for preparing an acrylate-modified polyurethane hot melt adhesive, step S1 may specifically include: first mixing an acrylate monomer, an alkali metal salt, a polyol compound, and a water absorbent, and then performing vacuum dehydration to obtain a pretreated product; then performing a first mixing treatment on the pretreated product with a polyisocyanate compound and a catalyst to obtain an acrylate-modified polyurethane prepolymer mixture. The vacuum dehydration conditions include: a temperature preferably of 100 to 120° C., such as 100° C., 105° C., 110° C., 115° C., 120° C., or any value therebetween; a time preferably of 1 to 5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or any value therebetween; a stirring speed preferably of 100 to 200 r / min, such as 100 r / min, 120 r / min, 150 r / min, 180 r / min, 200 r / min, or any value therebetween; and a vacuum degree that can be conventionally selected in the art. The conditions of the first mixing treatment include: the temperature is preferably 70-90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C or any value therebetween; the time is preferably 1-5h, such as 1h, 2h, 3h, 4h, 5h or any value therebetween; the stirring speed is preferably 100-200r / min, such as 100r / min, 120r / min, 150r / min, 180r / min, 200r / min or any value therebetween; and the treatment is preferably carried out under vacuum conditions, and the degree of vacuum can be a conventional choice in the art.

[0036] In the above-mentioned preparation method of acrylate modified polyurethane hot melt adhesive, in step S2, the conditions of the second mixing treatment include: the temperature is preferably 70-90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C or any value therebetween; the time is preferably 0.5-2h, such as 0.5h, 0.75h, 1h, 1.5h, 2h or any value therebetween; the stirring speed is preferably 100-200r / min, such as 100r / min, 120r / min, 150r / min, 180r / min, 200r / min or any value therebetween; and the treatment is preferably carried out under vacuum conditions, and the degree of vacuum can be a conventional choice in the art.

[0037] The acrylate-modified polyurethane hot melt adhesive provided by the present invention can be applied to products that require adhesive removal and whose adhesive substrates can be electrified. Specifically, the adhesive removal conditions include: the voltage for electrified disassembly can be 1 to 100V, such as 1V, 3V, 5V, 7V, 9V, 10V, 20V, 50V, 60V, 80V, 100V, or any value therebetween; the electrified disassembly time can be 1s to 60min, such as 1s, 2s, 5s, 10s, 20s, 30s, 50s, 1min, 2min, 5min, 10min, 20min, 30min, 40min, 50min, 60min, or any value therebetween. In addition, the adhesive substrate used by the acrylate-modified polyurethane hot melt adhesive is a conductive substrate.

[0038] The present invention will be described in detail below through specific examples.

[0039] The parts involved in the following examples and comparative examples are all parts by weight.

[0040] The raw materials and sources in the following examples and comparative examples are as follows:

[0041] Polyhexanediol adipate diol, purchased from Qingdao Xinyutian Chemical Co., Ltd., brand POL-538, Mn = 3000 g / mol; polyoxypropylene ether diol, purchased from Dow Chemical Company, brand Voranol-2120, Mn = 2000 g / mol; polytetrahydrofuran ether diol, purchased from BASF, brand PolyTHF 1000, Mn = 1000 g / mol; polyneopentyl adipate diol, purchased from Qingdao Xinyutian Chemical Co., Ltd., brand POL-756, Mn = 2000 g / mol; polyester polyol, purchased from Evonik Specialty Chemicals, brand DYNACOLL 7360, Mn = 3500 g / mol; polyoxypropylene ether diol, purchased from Dow Chemical Company, brand Voranol-220-110, Mn = 1000 g / mol; polycaprolactone diol, purchased from Daicel Corporation, brand PLACCEL 240, Mn = 4000 g / mol; poly (ethylene glycol phthalate) diol, purchased from Stepan Company, brand PS-70L, Mn = 1600 g / mol; poly (1,5-pentanediol-1,6-hexanediol) carbonate diol, purchased from Asahi Kasei Chemicals Corporation, brand Duranol T5652, Mn = 2000 g / mol.

[0042] The p-toluenesulfonyl isocyanate water absorbent was purchased from Borchers, Germany, with the brand name Additive TI; the triethyl orthoformate water absorbent was purchased from Borchers, Germany, with the brand name Additive OF; and the adsorbent molecular sieve water absorbent was purchased from ARkEMA, with the brand name Siliporite SA1702.

[0043] Example 1

[0044] 32.65 parts of polyhexanediol adipate diol POL-538, 21.77 parts of polyoxypropylene ether diol Voranol-2120, 12.00 parts of 2-phenoxyethyl acrylate (viscosity 7-12 mPa.s at 25°C), 13.00 parts of 1,6-hexanediol diacrylate (viscosity 5-8 mPa.s at 25°C), 7.00 parts of lithium trifluoromethanesulfonate, 0.50 parts of water absorbent additive TI was added to a reaction flask, heated to 110°C, and vacuum dehydrated for 2 h at 150 r / min stirring; then cooled to 80°C, 10.88 parts of 4,4'-diphenylmethane diisocyanate (MDI) and 0.20 parts of stannous octoate were added, and the mixture was reacted for 2 h at 150 r / min stirring to obtain an acrylate-modified polyurethane prepolymer mixture; then 1.00 parts of photoinitiator 184 and 1.00 parts of 3-mercaptopropyltrimethoxysilane were added, and the mixture was mixed for 1 h at 150 r / min stirring before discharging to obtain an acrylate-modified polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0045] Example 2

[0046] 37.81 parts of polytetramethylene ether glycol PolyTHF 1000, 25.21 parts of polyneopentyl adipate glycol POL-756, 5.00 parts of 1,4-butanediol diacrylate (viscosity of 2-10 mPa.s at 25°C), 5.00 parts of tetramethylene acrylate (viscosity of 2-5 mPa.s at 25°C), 3.00 parts of lithium bis(trifluoromethanesulfonyl)imide, 0.10 parts of water absorbent additive OF was added to the reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours at 150 r / min; then cooled to 80°C, 22.69 parts of 4,4'-diphenylmethane diisocyanate (MDI) and 0.50 parts of dibutyltin dilaurate were added, and the mixture was stirred at 150 r / min for 2 hours to obtain an acrylate-modified polyurethane prepolymer mixture; then 0.50 parts of photoinitiator 819 and 0.20 parts of 3-glycidoxypropyltrimethoxysilane were added, and the mixture was stirred at 150 r / min for 1 hour before discharging to obtain an acrylate-modified polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0047] Example 3

[0048] 30.45 parts of polyester polyol DYNACOLL 7360, 8.70 parts of polyoxypropylene ether glycol Voranol-220-110, 15.00 parts of tripropylene glycol diacrylate (viscosity of 10-15 mPa.s at 25°C), 15.00 parts of tridecyl acrylate (viscosity of 3-11 mPa.s at 25°C), 15.00 parts of lithium tetrafluoroborate, 1.00 parts of water absorbent Siliporite SA1702 was added to the reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours at 150 r / min; then the temperature was lowered to 80°C, 5.85 parts of hexamethylene diisocyanate (HDI) and 0.20 parts of 2,2-dimorpholinodiethyl ether were added, and the mixture was reacted for 2 hours at 150 r / min to obtain an acrylate-modified polyurethane prepolymer mixture; then 3.00 parts of photoinitiator TPO and 2.00 parts of 3-isocyanatepropyltrimethoxysilane were added, and the mixture was mixed for 1 hour at 150 r / min and then discharged to obtain an acrylate-modified polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0049] Example 4

[0050] 43.65 parts of polycaprolactone diol PLACCEL 240, 10.91 parts of polyoxypropylene ether diol Voranol-220-110, 10.00 parts of tripropylene glycol diacrylate (viscosity at 25°C: 10-15 mPa.s), 10.00 parts of trimethylolpropane formal acrylate (viscosity at 25°C: 12-18 mPa.s), 9.00 parts of lithium hexafluorophosphate, and 1.00 part of water absorbent Additive TI were added to a reaction flask, heated to 110°C, and vacuum dehydrated for 2 h with stirring at 150 r / min; Then the temperature was lowered to 80°C, 11.44 parts of 4,4-diisocyanate dicyclohexylmethane (HMDI) and 1.00 parts of dibutyltin dilaurate were added, and the mixture was reacted at 150 r / min for 2 hours to obtain an acrylate-modified polyurethane prepolymer mixture; then 4.00 parts of photoinitiator ITX and 0.50 parts of 3-glycidoxypropyltrimethoxysilane were added, and the mixture was mixed at 150 r / min for 1 hour before discharging to obtain an acrylate-modified polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0051] Example 5

[0052] 36.84 parts of polyethylene phthalate diol PS-70L, 23.03 parts of polycarbonate-1,5-pentanediol-1,6-hexanediol ester diol Duranol T5652, 10.00 parts of neopentyl glycol diacrylate (viscosity of 10 mPa.s at 25°C), 5.00 parts of isodecyl acrylate (viscosity of 2-8 mPa.s at 25°C), 4.00 parts of potassium trifluoromethanesulfonate, 1.50 parts of water absorbent additive OF was added to the reaction flask, heated to 110°C, and vacuum dehydrated for 2 hours at 150 r / min; then cooled to 80°C, 15.33 parts of isophorone diisocyanate (IPDI) and 0.50 parts of stannous octoate were added, and the mixture was reacted for 2 hours at 150 r / min to obtain an acrylate-modified polyurethane prepolymer mixture; then 2.00 parts of photoinitiator 369 and 1.50 parts of 3-mercaptopropyltrimethoxysilane were added, and the mixture was mixed for 1 hour at 150 r / min and then discharged to obtain an acrylate-modified polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0053] Example 6

[0054] An acrylate-modified polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the same number of alkoxylated nonylphenol acrylates with a viscosity of 100-160 mPa.s at 25°C were used instead of 2-phenoxyethyl acrylate (viscosity of 7-12 mPa.s at 25°C) and 1,6-hexanediol diacrylate (viscosity of 5-8 mPa.s at 25°C). The other conditions were the same as those in Example 1, thereby obtaining an acrylate-modified polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0055] Example 7

[0056] Acrylate modified polyurethane hot melt adhesive was prepared according to the method of Example 1, except that lithium nitrate was used instead of lithium trifluoromethanesulfonate in the same amount. The other conditions were the same as those in Example 1, thereby obtaining acrylate modified polyurethane hot melt adhesive, which was vacuum sealed and stored away from light.

[0057] Comparative Example 1

[0058] A reference polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the same parts of propylene carbonate were used instead of 2-phenoxyethyl acrylate and 1,6-hexanediol diacrylate. The other conditions were the same as those in Example 1, thereby obtaining a reference polyurethane hot melt adhesive.

[0059] Comparative Example 2

[0060] A reference polyurethane hot melt adhesive was prepared according to the method of Example 1, except that 2-phenoxyethyl acrylate and 1,6-hexanediol diacrylate were not added. The other conditions were the same as those of Example 1, thereby obtaining a reference polyurethane hot melt adhesive.

[0061] Comparative Example 3

[0062] A reference polyurethane hot melt adhesive was prepared according to the method of Example 1, except that lithium trifluoromethanesulfonate was not added. The other conditions were the same as those of Example 1, thereby obtaining a reference polyurethane hot melt adhesive.

[0063] Comparative Example 4

[0064] A reference polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the addition amounts of 2-phenoxyethyl acrylate and 1,6-hexanediol diacrylate were increased to 30.00 parts. The other conditions were the same as those in Example 1, thereby obtaining a reference polyurethane hot melt adhesive.

[0065] Test Case

[0066] The polyurethane hot melt adhesives prepared in the above examples and comparative examples were tested for adhesion performance, heat resistance, and high temperature and high humidity resistance before and after power-on according to the following methods. The results are shown in Table 1.

[0067] (1) Adhesive strength test at different curing times before power on: The hot melt adhesive obtained in the embodiment and the comparative example was dispensed at 110°C using a dispensing machine to apply a 25mm*4mm rectangular adhesive line on a stainless steel substrate; the adhesive was then irradiated with 2000mJ / cm2 of UV-LED light at 365nm. 2 Energy, after the irradiation, another stainless steel substrate was bonded on the stainless steel substrate. After the bonding was completed, the samples were cured in an environment of 25℃ and 50% RH for 1 min, 15 min and 1 d respectively. The prepared bonding sample was run along the shear direction at a speed of 10 mm / min using a universal material testing machine until the bonding failed. The maximum force value displayed by the instrument was recorded, and the shear bonding strength of the adhesive to the stainless steel substrate after curing for 1 min, 15 min and 1 d was calculated based on the bonding area.

[0068] (2) Bonding strength after power-on: The sample to be tested was obtained after the glue was dispensed and cured for 1 day according to the method in (1). The positive and negative wires of the DC power supply were clamped at the two ends of the sample respectively. The power was applied at a voltage of 48V or 60V for 30min or 20min. After the power-on was completed, the sample was removed. The prepared bonding sample was run along the shear direction at a speed of 10mm / min using a universal material testing machine until the bonding of the sample failed. The maximum force value displayed by the instrument was recorded. The shear bonding strength of the adhesive to the stainless steel substrate after power-on was calculated based on the bonding area (when the bonding strength is below 2MPa, it is detachable).

[0069] (3) Heat resistance (80°C): The sample to be tested was obtained after curing for 1 day according to the method in (1). The bonded sample was placed in an 80°C oven for 20 minutes. The prepared bonded sample was run in an 80°C environment at a speed of 10 mm / min along the shear direction using a universal material testing machine until the sample failed to bond. The maximum force value displayed by the instrument was recorded, and the shear bonding strength of the adhesive to the stainless steel substrate in a high temperature environment of 80°C was calculated based on the bonding area.

[0070] (4) Resistance to high temperature and high humidity (85°C, 85% RH): The sample to be tested was obtained after curing for 1 day according to the method in (1). The bonded sample was placed in a high temperature and high humidity oven at 85°C and 85% RH for 7 days. The prepared bonding sample was run in the shear direction at a speed of 10 mm / min using a universal material testing machine until the bonding of the sample failed. The maximum force value displayed by the instrument was recorded, and the shear bonding strength of the adhesive to the stainless steel substrate after high temperature and high humidity aging was calculated based on the bonding area.

[0071] Table 1

[0072]

[0073] As can be seen from the results of Examples 1 to 7, the bonding strength of the acrylate-modified polyurethane hot melt adhesive provided by the present invention after energization is greatly reduced, reduced to less than 2MPa, with detachability, and also has excellent bonding performance before energization, with high bonding strength and good heat resistance and high temperature and high humidity resistance. As can be seen from the results of Example 1 and Comparative Example 1, compared to the traditional polyurethane hot melt adhesive with the addition of alkali metal salt and solvated matrix (propylene carbonate), the acrylate-modified polyurethane hot melt adhesive provided in Example 1 not only has a bonding strength after energization reduced to less than 2MPa, but also has detachability, but also has better bonding performance (high bonding strength and good heat resistance and high temperature and high humidity resistance). As can be seen from the results of Example 1 and Comparative Example 2 and Comparative Example 3, the lack of any component in acrylate monomer and alkali metal salt not only does not significantly decrease the bonding strength after energization, but the bonding strength is still higher than 2MPa, without detachability, and the bonding strength, heat resistance and high temperature and high humidity resistance of the polyurethane hot melt adhesive before energization are all worse than Example 1. From the results of Example 1 and Comparative Example 4, it can be seen that when the amount of acrylate added is too large, the bonding performance (bonding strength before power-on, heat resistance, and high temperature and high humidity resistance) will be greatly reduced.

[0074] In summary, the acrylate-modified polyurethane hot melt adhesive provided by the present invention has both excellent bonding properties (high bonding strength and good heat resistance and high temperature resistance) and electrical disassembly properties, and has broad practical application prospects.

[0075] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. An acrylate modified polyurethane hot melt adhesive, characterized in that: The raw materials for preparing the acrylate-modified polyurethane hot melt adhesive contain acrylate monomer, alkali metal salt, polyol compound, polyisocyanate compound, photoinitiator and optional silane coupling agent, catalyst and water absorbent; the content of the acrylate monomer is 10 to 30 parts by weight, the content of the alkali metal salt is 3 to 15 parts by weight, the content of the polyol compound is 35 to 66 parts by weight, and the content of the polyisocyanate compound is 5 to 25 parts by weight.

2. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The content of the photoinitiator is 0.5 to 5 parts by weight, the content of the silane coupling agent is 0 to 3 parts by weight, the content of the catalyst is 0 to 2 parts by weight, and the content of the water absorbent is 0 to 2 parts by weight.

3. The acrylate modified polyurethane hot melt adhesive according to claim 1, characterized in that: The viscosity of the acrylic acid ester monomer at 25° C. is 0.1 to 30 mPa.s.

4. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The acrylate monomer is selected from at least one of octadecyl acrylate, tetrahydrofuran acrylate, dodecyl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, isooctyl acrylate, tridecyl acrylate, trimethylolpropane formal 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 and dipropylene glycol diacrylate.

5. The acrylate modified polyurethane hot melt adhesive according to claim 1, characterized in that: The alkali metal salt is a compound composed of an alkali metal cation and at least one anion selected from the group consisting of an organic acid anion, an inorganic acid anion, and an organic sulfonyl imide anion.

6. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The alkali metal salt is selected from at least one of lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium chloride, lithium sulfate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroantimonate, lithium nitrate, sodium trifluoromethanesulfonate, sodium bistrifluoromethanesulfonyl imide, sodium chloride, sodium sulfate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroantimonate, sodium nitrate, potassium trifluoromethanesulfonate, potassium bistrifluoromethanesulfonyl imide, potassium chloride, potassium sulfate, potassium nitrate, potassium tetrafluoroborate, potassium hexafluorophosphate and potassium hexafluoroantimonate.

7. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The polyol compound is at least one selected from polyester polyol, polyether polyol, polycarbonate polyol and polyalkylene polyol.

8. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The number average molecular weight of the polyol compound is 1000 to 4000 g / mol.

9. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The polyisocyanate compound is at least one selected from the group consisting 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, m-xylylene diisocyanate, tetramethylxylylene diisocyanate, norbornane dimethylene isocyanate, lysine diisocyanate, triphenylmethane triisocyanate, thiophosphoric acid triphenyl isocyanate, and 1,6,11-undecane triisocyanate.

10. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The photoinitiator is selected from at least one of benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, oxime ester compounds, benzoin ether compounds and thioxanthone.

11. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The silane coupling agent is selected from at least one of mercaptosilane, epoxysilane, aminosilane, alkenylsilane and isocyanatesilane.

12. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine and 2,2-dimorpholinyl diethyl ether.

13. The acrylate-modified polyurethane hot melt adhesive according to claim 1, characterized in that: The water absorbent is selected from at least one of a molecular sieve desiccant, an oxazolidine desiccant, p-methylbenzenesulfonyl isocyanate and triethyl orthoformate.

14. The method for preparing the acrylate-modified polyurethane hot melt adhesive according to any one of claims 1 to 13, characterized in that: The method comprises the steps of uniformly mixing an acrylate monomer, an alkali metal salt, a polyol compound, a polyisocyanate compound, a photoinitiator, and an optional silane coupling agent, a catalyst, and a water absorbent to obtain an acrylate-modified polyurethane hot melt adhesive.

15. Use of the acrylate modified polyurethane hot melt adhesive according to any one of claims 1 to 13 in bonding electronic products.

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