Electrically-dismountable UV moisture curing reaction type polyurethane hot melt adhesive with excellent adhesive property and low free isocyanate content as well as preparation method and application of electrically-dismountable UV moisture curing reaction type polyurethane hot melt adhesive

Abstract

The invention belongs to the field of polyurethane hot melt adhesives, and particularly relates to a UV moisture curing reaction type polyurethane hot melt adhesive which is excellent in adhesive performance, low in free isocyanate content and capable of being electrically disassembled, and a preparation method and application thereof. The preparation raw materials of the UV moisture curing reaction type polyurethane hot melt adhesive comprise an acrylate monomer, an alkali metal salt, a polyol compound, a low free polyurethane prepolymer, a photoinitiator, and an optional silane coupling agent, a water absorbent and a catalyst. The mass ratio of the acrylate monomer to the alkali metal salt is (1-10): 1; the mass ratio of the acrylate monomer to the polyol compound to the low free polyurethane prepolymer is 1: (0.4-2.9): (1-6); the content of free isocyanate in the low-free polyurethane prepolymer is less than or equal to 0.1 wt%. The UV moisture curing reaction type polyurethane hot melt adhesive which is excellent in adhesive property, low in free isocyanate content and capable of being electrically disassembled is prepared by introducing the photocurable acrylate monomer and the alkali metal salt in a specific proportion.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane hot melt adhesives, and specifically relates to a UV moisture-curing reactive polyurethane hot melt adhesive with excellent bonding performance, low free isocyanate content and electrical disassembly, as well as a preparation method and application thereof. Background Art

[0002] Reactive polyurethane hot melt adhesive is an adhesive with isocyanate-terminated oligomers as the main resin. It mainly forms a cross-linked chemical structure through the moisture curing reaction of isocyanate and air to achieve high bonding strength. It is often used to bond and fix parts of electronic products such as smartphones, tablets, smart watches, and TWS headphones. However, since isocyanate-terminated oligomers are mainly obtained by reacting polyols with excess isocyanate monomers, there are reasons such as insufficient reaction between polyols and excess isocyanate monomers and hindered reaction under high viscosity, resulting in a large amount of unreacted free isocyanate monomers (>1wt%) in the final polyurethane hot melt adhesive. Free isocyanate monomers will vaporize at 85-200°C to form irritating, allergic or toxic substances, which will endanger the health of practitioners. In addition, since electronic product components are often of high value, when poor assembly, after-sales product repairs, and recycling of valuable electronic product components occur, it is usually necessary to disassemble some of the bonded components. However, the covalent bonds obtained by the reaction of isocyanate and moisture are irreversible, and the cross-linked structure is difficult to destroy. It is usually difficult to disassemble the adhesive after it is fully cured. Once there is a need to disassemble the bonded samples, it will require a lot of manpower, material resources, and financial resources, increasing the cost of adhesive disassembly.

[0003] At present, by introducing alkali metal salts and solvated matrices into polyurethane hot melt adhesives, the bonding strength at the bonding interface decreases after power is applied, thereby realizing the function of electrical disassembly. However, although the existing electrically disassembled polyurethane hot melt adhesives have the function of being disassembled under power-on conditions, there is still a large gap between them and the traditional widely used polyurethane hot melt adhesives in terms of bonding strength, curing speed, heat resistance and other properties. In other words, the electrically disassembled polyurethane hot melt adhesives developed by the prior art are still difficult to meet the performance requirements of actual application scenarios. Therefore, it is urgent to develop a UV moisture-cured polyurethane hot melt adhesive with low free isocyanate monomer content, disassembleable under power-on conditions, and excellent bonding performance to meet the future market's application needs for high-performance detachable UV moisture-cured reactive polyurethane hot melt adhesives. Summary of the invention

[0004] The purpose of the present invention is to provide a UV moisture-curable reactive polyurethane hot melt adhesive with excellent bonding performance, low free isocyanate content and electrical disassembly, as well as a preparation method and application thereof, in view of the defects of the existing electrically disassemblyable reactive polyurethane hot melt adhesive, such as poor bonding performance and high free isocyanate content.

[0005] In the first aspect, the present invention provides a UV moisture-curing reactive polyurethane hot melt adhesive, wherein the raw materials for preparing the polyurethane hot melt adhesive contain acrylate monomer, alkali metal salt, polyol compound, low-free polyurethane prepolymer, photoinitiator, and optional silane coupling agent, water absorbent and catalyst; the mass ratio of the acrylate monomer to the alkali metal salt is (1-10):1; the mass ratio of the acrylate monomer to the polyol compound and low-free polyurethane prepolymer is 1:(0.4-2.9):(1-6); the free isocyanate content in the low-free polyurethane prepolymer is ≤0.1wt%.

[0006] In a preferred embodiment, 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 10 to 30 parts by weight, the content of the low free polyurethane prepolymer is 30 to 60 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 water absorbent is 0 to 2 parts by weight, and the content of the catalyst is 0 to 2 parts by weight.

[0007] In a preferred embodiment, the viscosity of the acrylic acid ester monomer at 25° C. is 0.1 to 30 mPa.s.

[0008] In a preferred embodiment, 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.

[0009] In a preferred embodiment, 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.

[0010] In a preferred embodiment, 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.

[0011] In a preferred embodiment, the polyol compound is selected from at least one of polyester polyol I, polyether polyol I, polycarbonate polyol and polyalkylene polyol.

[0012] In a preferred embodiment, the number average molecular weight of the polyol compound is 1000 to 4000 g / mol.

[0013] In a preferred embodiment, the low-free polyurethane prepolymer is a low-free polyether polyol-based polyurethane prepolymer and / or a low-free polyester polyol-based polyurethane prepolymer.

[0014] In a preferred embodiment, 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.

[0015] In a preferred embodiment, the silane coupling agent is selected from at least one of mercaptosilane, epoxysilane, aminosilane, alkenylsilane and isocyanatesilane.

[0016] In a preferred embodiment, the water absorbent is selected from at least one of a molecular sieve desiccant, an oxazolidine dehydrating agent, p-toluenesulfonyl isocyanate and triethyl orthoformate.

[0017] In a preferred embodiment, the catalyst is at least one selected from dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine and 2,2-dimorpholinyl diethyl ether.

[0018] In a second aspect, the present invention provides a method for preparing the above-mentioned UV moisture-curing reactive polyurethane hot melt adhesive, which comprises: mixing an acrylate monomer, an alkali metal salt, a polyol compound, a low-free polyurethane prepolymer, a photoinitiator, and an optional silane coupling agent, a water absorbent, and a catalyst to obtain a UV moisture-curing reactive polyurethane hot melt adhesive.

[0019] In a third aspect, the present invention also provides the use of the above-mentioned UV moisture-curing reactive polyurethane hot melt adhesive in the bonding of electronic products.

[0020] After extensive and in-depth research, the inventors of the present invention have found that the reason why the existing electrically disassembled polyurethane hot melt adhesive has poor bonding performance may be that its electrically disassembled performance is mainly achieved by introducing alkali metal salts and solvated matrices to form a liquid electrolyte. Under the condition of power on, the charged ions in the liquid electrolyte migrate under the action of the electric field to produce a Faraday electrochemical reaction, thereby weakening the bonding strength at the adhesive interface and realizing the function of the adhesive being electrically disassembled. However, since the liquid electrolyte cannot undergo a curing reaction, it still exists in the adhesive system in its initial liquid form after the adhesive is cured, that is, a "plasticizer" is formed in the cured colloid. The "plasticizer" affects the internal structure of the cured colloid and has a negative impact on the bonding strength of the adhesive, causing a significant decrease in the bonding strength. Therefore, how to solve the problem of the presence of "plasticizers" in the cured colloid is the key to improving the bonding performance of electrically disassembled polyurethane hot melt adhesives.

[0021] Based on this, the present invention creatively introduces a specific ratio of photocurable acrylate monomers and alkali metal salts into the reactive polyurethane hot melt adhesive, and regulates the ratio of acrylate monomers to polyol compounds and low-free polyurethane prepolymers, thereby obtaining a UV moisture-curable reactive polyurethane hot melt adhesive that not only has electrically disassemblyable properties, but also has excellent bonding properties and low free isocyanate content. The reason may be speculated to be that: by introducing a specific ratio of photocurable acrylate monomers and alkali metal salts, on the one hand, the acrylate monomers, as a solvating matrix, can dissolve the alkali metal salts well and make them evenly distributed in the UV moisture-curing reactive polyurethane hot melt adhesive. Under the condition of power on, a Faraday chemical reaction will occur at the colloid bonding interface, which will significantly reduce the bonding strength, thereby achieving the performance of electrical disassembly; on the other hand, the acrylate monomers can undergo a curing reaction by light in the presence of a photoinitiator, which not only solves the problem that the existing solvating matrix is ​​difficult to cure, but also, compared with the traditional reactive polyurethane hot melt adhesive that relies on the moisture curing reaction of isocyanate and air, the UV moisture-curing reactive polyurethane hot melt adhesive has a faster curing speed, thereby effectively improving the curing speed and achieving excellent bonding performance. At the same time, the ionic conductivity of the acrylate monomer decreases less after curing than when it is not cured, which has a positive effect on the cured body The ion migration ability of the system is very little affected. It is speculated that this may be because in addition to being affected by the effect of the solvated matrix, ion migration is also related to the dipole interaction between the dissociated ions and the polymer segments. The movement of the polymer segments can help ion migration, so the acrylate monomer can still maintain good electrical disassembly performance after curing; by controlling the ratio of acrylate monomer to polyol compound and polyisocyanate compound, the UV moisture-curing reactive polyurethane hot melt adhesive can quickly establish initial bonding strength after UV curing, and at the same time can 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+moisture-curing reactive 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. In addition, by introducing a low-free polyurethane prepolymer with a free isocyanate content of ≤0.1wt% to replace the isocyanate monomer required for the traditional preparation of polyurethane hot melt adhesive, the free isocyanate content in the colloid can be effectively reduced, greatly improving the safety of using UV moisture-reactive polyurethane hot melt adhesive.

[0022] In summary, the UV moisture-curing reactive polyurethane hot melt adhesive provided by the present invention has the advantages of excellent bonding performance, low free isocyanate content, and electrical disassembly, and is expected to meet the application needs of high-performance adhesives that can be disassembled on demand in the future market, and has broad application prospects. DETAILED DESCRIPTION

[0023] The raw materials for preparing the UV moisture curing reactive polyurethane hot melt adhesive provided by the present invention contain acrylate monomers, alkali metal salts, polyol compounds, low-free polyurethane prepolymers, photoinitiators, and optional silane coupling agents, water absorbents, and catalysts. 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:(0.4-2.9), such as 1:0.4, 1:0.6, 1:0.8, 1:1, 1:2, 1:2.5, 1:2.9, or any value therebetween. The mass ratio of the acrylate monomer to the low-free polyurethane prepolymer is (1-6), such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, or any value therebetween. When the content of acrylate monomer is too high, the adhesion of the colloid surface is greatly reduced due to the fast curing reaction of acrylate after UV light exposure and the high degree of curing, thereby reducing the adhesion between the interface of the UV moisture curing reactive polyurethane hot melt adhesive and the bonded substrate, and the bonding strength after the final curing is also greatly reduced. Therefore, in addition to controlling the mass ratio of acrylate monomer to alkali metal salt so that the UV moisture curing reactive polyurethane hot melt adhesive has good electrical conductivity, it is also necessary to regulate the mass ratio of acrylate monomer to polyol compound and polyisocyanate compound, and each component cooperates with each other, so as to simultaneously improve the curing speed and bonding strength of the UV moisture curing reactive polyurethane hot melt adhesive. The free isocyanate content in the low free polyurethane prepolymer is ≤0.1wt%.

[0024] 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, 8, 10, 12, 15 parts by weight or any value therebetween; the content of the polyol compound 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 low free polyurethane prepolymer is preferably 30 to 60 parts by weight, such as 30, 35, 40, 45, 50, 55, 60 parts by weight or any value therebetween; the photoinitiator The content of the hair dryer is preferably 0.5-5 parts by weight, such as 0.5, 0.8, 1, 2, 3, 4, 5 parts by weight or any value therebetween; the content of the silane coupling agent is preferably 0-3 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 water absorbent is preferably 0-2 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 catalyst is preferably 0-2 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.

[0025] In the present invention, 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, 8 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 at 25°C is controlled within the above preferred range, it is more conducive to the dissolution of the alkali metal by the acrylate monomer, and the alkali metal is better dispersed evenly in the UV moisture curing reactive polyurethane hot melt adhesive system, thereby giving the UV moisture curing reactive polyurethane hot melt adhesive good electrical disassembly performance. The present invention does not limit the specific type and source of the acrylate monomer, and specific examples thereof 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.

[0026] In the present invention, the alkali metal salt can be a compound composed of an alkali metal cation and an anion. 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), more 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, bistrifluoromethanesulfonyl imide ion and their substituted derivative ions. 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 give the polyurethane hot melt adhesive better electrical disassembly performance. 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, sodium trifluoromethanesulfonate, sodium bistrifluoromethanesulfonyl imide, sodium chloride, sodium sulfate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroantimonate, potassium trifluoromethanesulfonate, potassium bistrifluoromethanesulfonyl imide, potassium chloride, potassium sulfate, potassium tetrafluoroborate, potassium hexafluorophosphate and potassium hexafluoroantimonate.

[0027] In the present invention, the number average molecular weight (Mn) of the polyol compound is preferably 1000-4000 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. The type and source of the polyol compound can be various existing choices, preferably at least one of polyester polyol I, polyether polyol I, polycarbonate polyol and polyalkylene polyol. The polyester polyol I can be a polyester polyol obtained by the reaction of a polycarboxylic acid and a polyol, or a poly-ε-caprolactone polyol obtained by ring-opening polymerization of ε-caprolactone. The polycarboxylic acid may be 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 may be 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 polyether polyol I may be at least one of a random copolymer, a block copolymer and a bisphenol-type polyoxyalkylene modified body of ethylene glycol, propylene glycol, tetrahydrofuran, 3-methyltetrahydrofuran or a derivative thereof. The bisphenol-type polyoxyalkylene modified body is a polyether polyol obtained by adding alkylene oxide to the active hydrogen part of the bisphenol-type molecular skeleton, which can be a random copolymer and / or a block copolymer; the alkylene oxide is preferably at least one of ethylene oxide, propylene oxide, butylene oxide and isobutylene oxide. The polycarbonate polyol can be exemplified by at least one of polycarbonate-1,6-hexanediol ester diol, polycarbonate-1,4-butanediol-1,6-hexanediol ester diol, polycarbonate-1,5-pentanediol-1,6-hexanediol ester diol, polycarbonate-caprolactone hexanediol, polycarbonate-1,4-cyclohexanedimethanol-1,6-hexanediol ester diol, polyethylene carbonate diol, polypropylene carbonate diol, polybutylene carbonate diol and polyhexane carbonate diol. The polyalkylene polyol may illustratively be at least one of polybutadiene polyol, hydrogenated polybutadiene polyol, and hydrogenated polyisoprene polyol.

[0028] In the present invention, the low-free polyurethane prepolymer with a free isocyanate content of ≤0.1wt% may include only low-free polyether polyol-based polyurethane prepolymer, or only low-free polyester polyol-based polyurethane prepolymer, or both low-free polyether polyol-based polyurethane prepolymer and low-free polyester polyol-based polyurethane prepolymer. Specifically, the low-free polyether polyol-based polyurethane prepolymer may be commercially available, or may be obtained by reacting polyether polyol II with polyisocyanate monomer I. As commercially available low-free polyether polyol-based polyurethane prepolymers, examples thereof include: at least one of Adiprene LF TE 915, Adiprene LF TE 1050, Adiprene LF TE 980, Adiprene LF TE 330, Adiprene LF TE 365, Adiprene LF TE 440, Adiprene LF 900A, Adiprene LFM G730, Adiprene LFM G750, Adiprene LFM G600, Adiprene LFMI G600, and Adiprene LFMI G1000 from LANXESS. The low-free polyester polyol-based polyurethane prepolymer can be commercially available or obtained by reacting polyester polyol II with polyisocyanate monomer II. As a commercially available low-free polyester polyol-based polyurethane prepolymer, it can be exemplified as at least one of Adiprene LFM S200, Adiprene LFM S300, and Adiprene LFM S500 of Lanxess. Specific examples of the polyether polyol II and polyester polyol II are as described above, wherein the polyester polyol II is preferably at least one of polyethylene adipate glycol diol, polypropylene adipate glycol diol, polybutylene adipate glycol diol, polybutylene adipate glycol 1,4-diol diol, polyneopentyl adipate glycol diol, and polyhexane adipate glycol 1,6-diol diol. The polyisocyanate monomer I and the polyisocyanate monomer II are each independently preferably selected from at least one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, 1,4-phenylene diisocyanate, xylylene diisocyanate, tetramethylxylene diisocyanate and norbornane diisocyanate.

[0029] In the present invention, specific examples of the silane coupling agent 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-glycidoxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3 -At least one of 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.

[0030] The preparation method of the UV moisture curing reactive polyurethane hot melt adhesive provided by the present invention comprises: mixing acrylate monomers, alkali metal salts, polyol compounds, low-free polyurethane prepolymers, photoinitiators, and optional silane coupling agents, water absorbents and catalysts to obtain the UV moisture curing reactive polyurethane hot melt adhesive.

[0031] In a specific embodiment, the preparation method may be: S1. subjecting an acrylate monomer, an alkali metal salt, a polyol compound and an optional water absorbent to a vacuum dehydration treatment to obtain a pretreated product; S2. subjecting the pretreated product to a first mixing treatment with a low-free polyurethane prepolymer and an optional catalyst to obtain an acrylate-modified polyurethane prepolymer mixture; S3. subjecting the acrylate-modified polyurethane prepolymer mixture to a second mixing treatment with a photoinitiator and an optional silane coupling agent to obtain a UV moisture-curing reactive polyurethane hot melt adhesive, which is vacuum-sealed and stored away from light. Wherein, the conditions for the vacuum dehydration treatment may include: the temperature is preferably 100-120°C, such as 100°C, 105°C, 110°C, 115°C, 120°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. The conditions for the first mixing treatment may include: the temperature is preferably 70-90°C, such as 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°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; it is carried out under vacuum conditions, and the vacuum degree can be selected conventionally. The conditions of the second mixing treatment may include: the temperature is preferably 70-90°C, such as 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C, 90°C or any value therebetween; the time is preferably 0.5-2h, such as 0.5h, 0.8h, 1h, 1.2h, 1.5h, 1.8h, 2h or any value therebetween.

[0032] The UV moisture curing reactive polyurethane hot melt adhesive provided by the present invention is used in products that have a need for adhesive removal and the adhesive substrate has conductivity. Specifically, the conditions for adhesive removal include: the voltage is preferably 1 to 100V, such as 1V, 3V, 5V, 7V, 9V, 10V, 20V, 50V, 60V, 80V, 100V or any value therebetween, and the power-on time is preferably 1s to 60min, such as 1s, 2s, 15s, 30s, 40s, 50s, 1min, 2min, 5min, 10min, 20min, 30min, 40min, 50min, 60min or any value therebetween. In addition, the adhesive substrate used by the UV moisture curing reactive polyurethane hot melt adhesive is a conductive substrate.

[0033] The present invention will be described in detail below through specific embodiments.

[0034] The parts involved in the following examples and comparative examples are all parts by weight.

[0035] The raw materials and sources in the following examples and comparative examples are as follows:

[0036] Polybutylene adipate diol, purchased from Qingdao Xinyutian Chemical Co., Ltd., brand POL-338, Mn = 3000 g / mol; polyoxypropylene ether diol, purchased from Dow Chemical Company, brand Voranol-2120, Mn = 2000 g / mol; polyhexanediol adipate diol, purchased from Qingdao Xinyutian Chemical Co., Ltd., brand POL-5112, Mn = 1000 g / mol; polyester polyol DYNACOLL 7360, purchased from Evonik Specialty Chemicals, Mn = 3500 g / mol; polyneopentyl adipate diol, purchased from Qingdao Xinyutian Chemical Co., Ltd., brand POL-756, Mn = 2000 g / mol; polyester polyol DYNACOLL7380, purchased from Evonik Specialty Chemicals, Mn = 3500 g / mol; polyester polyol DYNACOLL 7210, purchased from Evonik Specialty Chemicals, Mn = 3500 g / mol; polycarbonate-1,5-pentanediol-1,6-hexanediol ester diol, purchased from Asahi Kasei Chemicals Co., Ltd., brand Duranol T5652, Mn = 2000 g / mol; polyhexanediol adipate diol, purchased from Qingdao Xinyutian Chemical Co., Ltd., brand POL-556, Mn = 2000 g / mol.

[0037] 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; the adsorbent molecular sieve water absorbent was purchased from ARkEMA, with the brand name Siliporite SA1702.

[0038] Example 1

[0039] 16.05 parts of polybutylene adipate diol POL-338, 10.70 parts of polyoxypropylene ether diol Voranol-2120, 10.00 parts of tripropylene glycol diacrylate (viscosity of 10-15 mPa.s at 25°C), 10.00 parts of trimethylolpropane formal acrylate (viscosity of 12-18 mPa.s at 25°C), 8.00 parts of lithium trifluoromethanesulfonate, and 0.50 parts of water absorbent Additive TI were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then cooled to 80°C, 27.55 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE 980 and 15.00 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300 and 0.20 parts of stannous octoate were reacted at 150 r / min stirring for 2 hours; then 1.00 parts of photoinitiator 184 and 1.00 parts of 3-glycidoxypropyltrimethoxysilane were added, and the mixture was mixed at 150 r / min stirring for 1 hour before discharging to obtain a UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0040] Example 2

[0041] 18.72 parts of polyoxypropylene ether diol Voranol-2120, 9.36 parts of polyhexanediol adipate diol POL-5112, 5.00 parts of tripropylene glycol diacrylate (viscosity of 10-15 mPa.s at 25°C), 5.00 parts of tridecyl acrylate (viscosity of 3-11 mPa.s at 25°C), 3.00 parts of lithium tetrafluoroborate, and 0.10 parts of water absorbent Siliporite SA1702 were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then cooled to 80°C, 48.12 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE 915 and 11.88 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S200 and 0.10 parts of 2,2-dimorpholinyl diethyl ether were reacted at 150 r / min stirring for 2 hours; then 0.50 parts of photoinitiator TPO and 0.10 parts of 3-isocyanate propyltrimethoxysilane were added, and the mixture was mixed at 150 r / min stirring for 1 hour before discharging to obtain a UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0042] Example 3

[0043] 7.75 parts of polyester polyol DYNACOLL 7360, 4.43 parts of poly (neopentyl adipate glycol ester) diol POL-756, 15.00 parts of 1,4-butanediol diacrylate (viscosity of 2-10 mPa.s at 25°C), 15.00 parts of tetrahydrofuran acrylate (viscosity of 2-5 mPa.s at 25°C), 15.00 parts of lithium bis (trifluoromethanesulfonyl imide), and 2.00 parts of water absorbent Additive OF were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then cooled to 80°C, 17.82 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE 915 and 13.00 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S500 and 2.00 parts of dibutyltin dilaurate were reacted at 150 r / min stirring for 2 hours; then 5.00 parts of photoinitiator 819 and 3.00 parts of 3-glycidoxypropyltrimethoxysilane were added, and the mixture was mixed at 150 r / min stirring for 1 hour before discharging to obtain UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0044] Example 4

[0045] 12.33 parts of polyester polyol DYNACOLL 7380, 12.33 parts of polyester polyol DYNACOLL 7210, 5.00 parts of 2-phenoxyethyl acrylate (viscosity of 7-12 mPa.s at 25°C), 8.00 parts of 1,6-hexanediol diacrylate (viscosity of 5-8 mPa.s at 25°C), 6.00 parts of lithium hexafluorophosphate, and 0.80 parts of water absorbent Additive TI were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then cooled to 80°C, 43.15 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF 900A and 8.00 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM were added. S300 and 0.70 parts of stannous octoate were reacted at 150 r / min stirring for 2 hours; then 2.20 parts of photoinitiator ITX and 1.50 parts of 3-mercaptopropyltrimethoxysilane were added, and the mixture was mixed at 150 r / min stirring for 1 hour before discharging to obtain a UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0046] Example 5

[0047] 4.29 parts of polycarbonate-1,5-pentanediol-1,6-hexanediol ester Duranol T5652, 8.59 parts of polyoxypropylene ether diol Voranol-2120, 15.00 parts of isodecyl acrylate (viscosity of 2-8 mPa.s at 25°C), 10.00 parts of neopentyl glycol diacrylate (viscosity of 10 mPa.s at 25°C), 13.00 parts of lithium hexafluorophosphate, and 1.50 parts of water absorbent Additive TI were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; then cooled to 80°C, 25.42 parts of low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE 440 and 15.00 parts of low-free polyester polyol-based polyurethane prepolymer Adiprene LFM were added. S300 and 1.20 parts of stannous octoate were reacted at 150 r / min stirring for 2 hours; then 3.50 parts of photoinitiator ITX and 2.50 parts of 3-mercaptopropyltrimethoxysilane were added, and the mixture was mixed at 150 r / min stirring for 1 hour before discharging to obtain a UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0048] Example 6

[0049] A UV moisture-curing reactive 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 tripropylene glycol diacrylate (viscosity of 10-15 mPa.s at 25°C) and trimethylolpropane formal acrylate (viscosity of 12-18 mPa.s at 25°C), and the other conditions were the same as those in Example 1, thereby preparing a UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0050] Example 7

[0051] A UV moisture-curing reactive polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the same amount of lithium nitrate was used instead of lithium trifluoromethanesulfonate, and the other conditions were the same as those of Example 1, thereby preparing a UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0052] Comparative Example 1

[0053] 25.48 parts of polyhexanediol adipate diol POL-556, 25.48 parts of polyoxypropylene ether diol Voranol-2120, 15.0 parts of acrylic resin BR106, 6.0 parts of lithium trifluoromethanesulfonate, 14.0 parts of propylene carbonate, 0.5 parts of water absorbent Additive TI, and 0.5 parts of 3-mercaptopropyltrimethoxysilane were added to a reaction bottle, heated to 110°C, and vacuum dehydrated for 2 hours under stirring conditions of 150 r / min; 12.74 parts of 4,4'-diphenylmethane diisocyanate (MDI) and 0.3 parts of stannous octoate were stirred at a speed of 150 r / min under vacuum conditions for 2 hours and then discharged to obtain a traditional electrically decomposable reactive polyurethane hot melt adhesive, which was vacuum sealed and stored.

[0054] Comparative Example 2

[0055] A reference UV moisture-curing reactive polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the same amount of 4,4'-diphenylmethane diisocyanate (MDI) was used instead of the low-free polyether polyol-based polyurethane prepolymer Adiprene LF TE980 and the low-free polyester polyol-based polyurethane prepolymer Adiprene LFM S300, and the other conditions were the same as in Example 1, thereby preparing a reference UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0056] Comparative Example 3

[0057] A reference UV moisture-curing reactive polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the same amount of propylene carbonate was used instead of tripropylene glycol diacrylate and trimethylolpropane formal acrylate, and the other conditions were the same as in Example 1, thereby preparing a reference UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0058] Comparative Example 4

[0059] A reference UV moisture-curing reactive polyurethane hot melt adhesive was prepared according to the method of Example 1, except that tripropylene glycol diacrylate and trimethylolpropane formal acrylate were not added, and the other conditions were the same as those in Example 1, thereby preparing a reference UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0060] Comparative Example 5

[0061] A reference UV moisture-curing reactive 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 preparing a reference UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0062] Comparative Example 6

[0063] A reference UV moisture-curing reactive polyurethane hot melt adhesive was prepared according to the method of Example 1, except that the addition amounts of tripropylene glycol diacrylate and trimethylolpropane formal acrylate were increased to 30 parts, and the other conditions were the same as those in Example 1, thereby preparing a reference UV moisture-curing reactive polyurethane hot melt adhesive, which was vacuum-sealed and stored away from light.

[0064] Test Case

[0065] The UV moisture curing reactive polyurethane hot melt adhesives prepared in the above examples and comparative examples were tested for bonding strength, heat resistance and high temperature and high humidity resistance before and after power on according to the following method. The results are shown in Table 1.

[0066] (1) Adhesive strength at different curing times before power on: At room temperature, the UV moisture-curable reactive polyurethane hot melt adhesive obtained in the embodiment and the comparative example was applied on a stainless steel substrate using a dispensing machine to apply a rectangular adhesive line of 25 mm*4 mm. After application, the adhesive was irradiated with a 365 nm UV-LED light source at 3000 mJ / cm 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 1min, 15min and 1d respectively. Then, 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, and the shear bonding strength of the adhesive to the stainless steel substrate after being cured for 1min, 15min and 1d was calculated based on the bonding area.

[0067] (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 turned on for 30 min or 20 min at a voltage of 48 V or 60 V. After the power-on was completed, the sample was removed and 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 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 power-on was calculated based on the bonding area (when the bonding strength is less than 2 MPa, it is removable).

[0068] (3) Heat resistance (80°C): The test samples were cured for 1 day according to the method in (1). The test samples were placed in an oven at 80°C for 20 min. The prepared bonding samples were then 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 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 in a high temperature environment of 80°C was calculated based on the bonding area.

[0069] (4) High temperature and high humidity resistance: The test sample was obtained after curing for 1 day according to the method in (1). The test 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.

[0070] (5) Free isocyanate content test: Use a high performance liquid chromatograph (HPLC) with liquid as the mobile phase and a high pressure infusion system to pump the mobile phase into a chromatographic column containing a stationary phase. After the components are separated in the column, they enter the detector for detection to obtain a chromatogram of the test substance. Use the external standard method to quantitatively calculate the content of free isocyanate monomers in the reactive polyurethane hot melt adhesive. Record the chromatograms of the sample to be tested and the standard separately. Calculate the content of free isocyanate in the sample to be tested based on the integrated area of ​​the specific peak on the chromatogram.

[0071] Table 1

[0072]

[0073] It can be seen from Examples 1 to 7 that the UV moisture-curing reactive polyurethane hot melt adhesive provided by the present invention has low free isocyanate content, high bonding strength, good heat resistance and high temperature and high humidity resistance, and the bonding strength after power-on is reduced to below 2MPa, and it is detachable. From the results of Example 1 and Comparative Example 1 and Comparative Example 3, it can be seen that compared with the traditional electrically disassembled reactive polyurethane hot melt adhesive (using non-curable propylene carbonate as the solvation matrix), the UV moisture-curing reactive polyurethane hot melt adhesive provided in Example 1 can not only achieve a significant reduction in bonding strength (reduced to below 2MPa) after power-on, and is detachable, but also has excellent bonding performance (fast curing speed, high bonding strength, heat resistance and good high temperature and high humidity resistance). From the results of Example 1 and Comparative Example 2, it can be seen that the use of low-free polyurethane prepolymer in Example 1 can effectively reduce the free isocyanate content of the colloid. From the results of Example 1 and Comparative Examples 4 and 5, it can be seen that the lack of any of the components of the acrylate monomer and the alkali metal salt not only reduces the bonding strength before power-on, the heat resistance, and the high temperature and high humidity resistance, but also the bonding strength after power-on does not decrease significantly, the bonding strength is still higher than 2MPa, and it is not removable. From the results of Example 1 and Comparative Example 6, it can be seen that when the amount of acrylate added is too large, the bonding performance (bonding strength before power-on, heat resistance, high temperature and high humidity resistance) will be greatly reduced, and it cannot meet the actual application requirements.

[0074] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary 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 intent of the present invention.

Claims

1. A UV moisture curing reactive polyurethane hot melt adhesive, characterized in that: The raw materials for preparing the UV moisture-curing reactive polyurethane hot melt adhesive contain acrylate monomer, alkali metal salt, polyol compound, low-free polyurethane prepolymer, photoinitiator and optional silane coupling agent, water absorbent and catalyst; the mass ratio of the acrylate monomer to the alkali metal salt is (1-10):1; the mass ratio of the acrylate monomer to the polyol compound and low-free polyurethane prepolymer is 1:(0.4-2.9):(1-6); the free isocyanate content in the low-free polyurethane prepolymer is ≤0.1wt%.

2. The UV moisture curing reactive polyurethane hot melt adhesive according to claim 1, characterized in that: 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 10 to 30 parts by weight, the content of the low-free polyurethane prepolymer is 30 to 60 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 water absorbent is 0 to 2 parts by weight, and the content of the catalyst is 0 to 2 parts by weight.

3. The UV moisture curing reactive 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; Preferably, 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.

4. The UV moisture curing reactive 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; Preferably, 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.

5. The UV moisture curing reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The polyol compound is selected from at least one of polyester polyol I, polyether polyol I, polycarbonate polyol and polyalkylene polyol; Preferably, the number average molecular weight of the polyol compound is 1000 to 4000 g / mol.

6. The UV moisture curing reactive polyurethane hot melt adhesive according to claim 1, characterized in that: The low-free polyurethane prepolymer is a low-free polyether polyol-based polyurethane prepolymer and / or a low-free polyester polyol-based polyurethane prepolymer.

7. The UV moisture curing reactive 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; Preferably, the silane coupling agent is selected from at least one of mercaptosilane, epoxysilane, aminosilane, alkenylsilane and isocyanatesilane.

8. The UV moisture curing reactive 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 dehydrating agent, p-toluenesulfonyl isocyanate and triethyl orthoformate; Preferably, the catalyst is at least one selected from dibutyltin dilaurate, stannous octoate, triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine and 2,2-dimorpholinyl diethyl ether.

9. The method for preparing the UV moisture curing reactive polyurethane hot melt adhesive according to any one of claims 1 to 8, characterized in that: The method comprises: mixing acrylate monomers, alkali metal salts, polyol compounds, low-free polyurethane prepolymers, photoinitiators, and optional silane coupling agents, water absorbents and catalysts to obtain UV moisture-curing reactive polyurethane hot melt adhesives.

10. Use of the UV moisture curing reactive polyurethane hot melt adhesive according to any one of claims 1 to 8 in bonding electronic products.

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