Polyurethane adhesive with high bonding strength and aging resistance as well as preparation method and application of polyurethane adhesive

Abstract

The invention belongs to the technical field of polyurethane adhesives, and particularly relates to a polyurethane adhesive with high bonding strength and aging resistance as well as a preparation method and application of the polyurethane adhesive. The polyurethane adhesive is prepared from an isocyanate-terminated polyurethane prepolymer, a modified silane coupling agent and an optional auxiliary agent, the isocyanate-terminated polyurethane prepolymer is obtained by carrying out polymerization reaction on polyol and polyisocyanate, and the polyol at least comprises polyphenyl ether dihydric alcohol and fluorine-containing dihydric alcohol; the modified silane coupling agent is obtained by carrying out modification reaction on aromatic dihydric alcohol and an unmodified silane coupling agent. The key point of the polyurethane adhesive is that polyphenyl ether dihydric alcohol and fluorine-containing dihydric alcohol are adopted as a polyhydric alcohol main body of the polyurethane adhesive, and an aromatic dihydric alcohol modified silane coupling agent is further introduced on the basis, so that the obtained polyurethane adhesive can have high bonding strength performance and high aging resistance performance at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethane adhesives, and particularly relates to a polyurethane adhesive with high bonding strength and aging resistance, and its preparation method and application. Background Art

[0002] Polyurethane adhesives are mainly composed of high molecular compounds formed by the reaction of isocyanates and polyols. Due to their excellent bonding properties, flexibility, wear resistance, and chemical resistance, they are widely used in many industries such as construction, automotive, electronics, packaging, and furniture. All along, polyurethane adhesives play an important role in the production and assembly of consumer electronics products. With the rapid development of technology, electronics products are more and more commonly used in people's daily lives and industries, and the materials and application scenarios used in electronics products are also more extensive, thus putting forward higher requirements for polyurethane adhesives: one is to have high bonding strength for various substrates (such as metals and materials with low surface energy such as glass and plastics); the second is that since electronics products may be used at different temperatures, it is required that polyurethane adhesives have good aging resistance; the third is that for some electronics products worn by the human body, it is also required that polyurethane adhesives have good chemical corrosion resistance.

[0003] Two-component polyurethane adhesives have the advantage of adjustable properties, and can have good bonding properties while realizing the adjustment of other properties by adjusting the components according to needs. However, they have strict requirements for the component ratio, and it is easy to have problems of poor bonding due to improper component mixing in the actual application process. Reactive polyurethane hot melt adhesives can well avoid the problem of poor bonding caused by improper component mixing, but they need to apply glue under high temperature conditions, which may cause certain damage to electronics products. Moisture-curing one-component polyurethane adhesives can apply glue and cure at room temperature, but their aging resistance is poor, and their bonding performance for some substrates with low surface energy is also poor. At present, there have been research reports that silicone, organofluorine, and polybutadiene can be introduced into moisture-curing one-component polyurethane adhesives in order to improve the bonding strength for substrates with low surface energy. However, due to the compatibility problems between silicone, organofluorine, polybutadiene and the polyurethane system, their improvement effect is limited and their aging resistance is poor. Therefore, it is urgent to develop a one-component moisture-curing polyurethane adhesive with high bonding strength and high aging resistance for substrates with low surface energy. Summary of the Invention

[0004] The purpose of the present invention is to provide a polyurethane adhesive with high bonding strength and aging resistance, and its preparation method and application, aiming at the problems of poor bonding strength and poor aging resistance of existing one-component moisture-curing polyurethane adhesives for substrates with low surface energy.

[0005] In a first aspect, the present invention provides a polyurethane adhesive. The polyurethane adhesive comprises: an isocyanate-terminated polyurethane prepolymer, a modified silane coupling agent, and an optional additive; the isocyanate-terminated polyurethane prepolymer is obtained by subjecting a polyol and a polyisocyanate to a polymerization reaction, wherein the polyol at least comprises a polyphenylene ether diol, a fluorinated diol, and a polyether diol; the modified silane coupling agent is obtained by subjecting an aromatic diol and an unmodified silane coupling agent to a modification reaction.

[0006] In a preferred embodiment, the mass ratio of the isocyanate-terminated polyurethane prepolymer, the modified silane coupling agent, and the additive is 100:(5 - 10):(0 - 10).

[0007] In a preferred embodiment, the molar ratio of the hydroxyl groups of the polyol to the isocyanate groups of the polyisocyanate is 1:(1.1 - 1.5).

[0008] In a preferred embodiment, the number average molecular weight of the polyphenylene ether diol is 500 - 2000 g / mol.

[0009] In a preferred embodiment, the fluorinated diol is selected from at least one of difluoro-1,3-propanediol, tetrafluoro-1,4-butanediol, hexafluoro-1,5-pentanediol, octafluoro-1,6-hexanediol, dodecafluoro-1,8-octanediol, perfluoro-1,9-nonanediol, and perfluoro-1,10-decanediol.

[0010] In a preferred embodiment, the number average molecular weight of the polyether diol is 500 - 3000 g / mol.

[0011] In a preferred embodiment, the polyisocyanate is an aliphatic diisocyanate and / or an aromatic diisocyanate.

[0012] In a preferred embodiment, the polymerization reaction of the polyol and the polyisocyanate comprises: subjecting the polyphenylene ether diol and the fluorinated diol to a first polymerization reaction in the presence of a first catalyst to obtain a diol prepolymer; then subjecting the diol prepolymer, the polyether diol, and the polyisocyanate to a second polymerization reaction in the presence of a second catalyst to obtain an isocyanate-terminated polyurethane prepolymer.

[0013] In a preferred embodiment, the molar ratio of the hydroxyl groups of the diol prepolymer and the polyether diol to the isocyanate groups of the polyisocyanate is 1:(1.1 - 1.5).

[0014] In a preferred embodiment, the molar ratio of the polyphenylene ether diol to the fluorinated diol is 1:(2 - 6).

[0015] In a preferred embodiment, the dosage of the first catalyst is 0.01-0.1 wt% of the total mass of the polyphenylene ether diol and the fluorinated diol.

[0016] In a preferred embodiment, the dosage of the second catalyst is 0.05-0.5 wt% of the mass of the polyisocyanate.

[0017] In a preferred embodiment, the first catalyst is a titanate catalyst.

[0018] In a preferred embodiment, the second catalyst is a tin-based catalyst and / or an amine catalyst.

[0019] In a preferred embodiment, the conditions of the first polymerization reaction include: temperature is 70-90 °C, and time is 12-24 h.

[0020] In a preferred embodiment, the conditions of the second polymerization reaction include: temperature is 40-80 °C, and time is 2-6 h.

[0021] In a preferred embodiment, the aromatic diol is bisphenol A and / or bisphenol F.

[0022] In a preferred embodiment, the siloxane functionality of the unmodified silane coupling agent is 3-4.

[0023] In a preferred embodiment, the unmodified silane coupling agent is selected from at least one of amino silane, mercapto silane, and epoxy silane.

[0024] In a preferred embodiment, the molar ratio of the aromatic diol to the unmodified silane coupling agent is 1:(1.2-1.5).

[0025] In a preferred embodiment, the modification reaction is carried out in the presence of an acidic catalyst.

[0026] In a preferred embodiment, the conditions of the modification reaction include: temperature is 30-50 °C, time is 2-6 h, and pH is 4-6.

[0027] In a preferred embodiment, the auxiliary agent is selected from at least one of a water scavenger, a rheology modifier, a leveling agent, a filler, an antifoaming agent, a diluent, and an adhesion promoter.

[0028] In a second aspect, the present invention provides a method for preparing the above polyurethane adhesive, the preparation method comprising: mixing polyphenylene ether diol, fluorinated diol and polyisocyanate for polymerization reaction to obtain an isocyanate-terminated polyurethane prepolymer, and then subjecting the isocyanate-terminated polyurethane prepolymer, a modified silane coupling agent and an optional auxiliary agent to a mixing treatment, and the resulting product is the polyurethane adhesive.

[0029] In a third aspect, the present invention also provides an application of the above polyurethane adhesive in the bonding of electronic products.

[0030] Beneficial effects: The key of the present invention lies in using polyphenylene ether diol, fluorinated diol and polyether diol as the polyol main body of the polyurethane adhesive. On the one hand, the compatibility of the polyurethane system is improved, the raw material components are mixed more uniformly, the cured colloid is more homogeneous, and the interaction force is strong, thereby improving the bonding strength to the substrate. On the other hand, introducing benzene rings and fluorine atoms into the molecular chain is beneficial to enhancing the cohesive strength of the polyurethane adhesive and the stability of the molecular chain, endowing the polyurethane adhesive with good aging resistance. On this basis, a silane coupling agent modified with aromatic diol is also introduced, which overcomes the problem that the introduced organopolysiloxane compounds will migrate with the increase of application time, resulting in a decrease in the bonding performance of the adhesive layer, improves the bonding strength performance of the polyurethane adhesive, and at the same time can better overcome the problem that the silane coupling agent is prone to hydrolysis and self-polymerization during storage. Moreover, the cross-linked structure formed by the silane coupling agent modified with aromatic diol has good heat resistance, which is beneficial to improving the aging resistance of the polyurethane adhesive. The resulting polyurethane adhesive can simultaneously have high bonding strength performance and high aging resistance. Specific embodiments

[0031] The polyurethane adhesive provided by the present invention comprises: an isocyanate-terminated polyurethane prepolymer, a modified silane coupling agent and an optional auxiliary agent; the isocyanate-terminated polyurethane prepolymer is obtained by polymerization reaction of a polyol and a polyisocyanate, wherein the polyol at least comprises polyphenylene ether diol, fluorinated diol and polyether diol; the modified silane coupling agent is obtained by modification reaction of an aromatic diol and an unmodified silane coupling agent. The two ends of the molecular chain of the isocyanate-terminated polyurethane prepolymer are isocyanate groups, and the middle chain segment can be a homopolymer, copolymer or block product of polyphenylene ether diol, fluorinated diol and polyisocyanate.

[0032] In the present invention, the mass ratio of the isocyanate-terminated polyurethane prepolymer, the modified silane coupling agent, and the auxiliary agent is preferably 100:(5-10):(0-10). Based on 100 parts by weight of the isocyanate-terminated polyurethane prepolymer, the content of the modified silane coupling agent is preferably 5-10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value therebetween; the content of the auxiliary agent is preferably 0-10 parts by weight, such as 0, 1, 2, 5, 8, 10 parts by weight or any value therebetween.

[0033] In the present invention, the molar ratio of the hydroxyl group of the polyol to the isocyanate group of the polyisocyanate is preferably 1:(1.1-1.5), such as 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or any value therebetween. The hydroxyl group of the polyol may at least include the hydroxyl group of polyphenylene ether diol and the hydroxyl group of fluorinated diol.

[0034] In the present invention, the number average molecular weight (Mn) of the polyphenylene ether diol is preferably 500-2000 g / mol, such as 500 g / mol, 800 g / mol, 1000 g / mol, 1200 g / mol, 1500 g / mol, 1800 g / mol, 2000 g / mol or any value therebetween.

[0035] In the present invention, the polyphenylene ether diol is preferably at least one of the compounds having the structure shown in formula (1), which can be purchased or prepared according to the existing disclosed methods. In formula (1), n and m are each independently preferably an integer of 1-15, such as 1, 2, 5, 8, 10, 12, 15 or any integer therebetween; R1-R4 are each independently preferably a hydrogen atom or a methyl group; X is preferably selected from at least one of -O-, -C(O)-, -C(CH3)2-, -CH2-.

[0036]

[0037] In the present invention, the preparation method of the polyphenylene ether diol may be as follows: Mix a monophenol, a catalyst, and optionally a diphenol to carry out an oxidative copolymerization reaction, and collect the reaction product to obtain the polyphenylene ether diol having the structure shown in formula (1). Among them, the monophenol is preferably 2,6-dimethylphenol. The diphenol is preferably bisphenol A and / or 2,2',4,4'-tetramethylbisphenol A. The catalyst is preferably a copper ammonia complex catalyst. The conditions of the oxidative copolymerization reaction preferably include: 40-70 °C, such as 40 °C, 50 °C, 60 °C, 70 °C or any value therebetween; the time is 2-4 h, such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h or any value therebetween.

[0038] In the present invention, specific examples of the fluorinated diol include, but are not limited to, at least one of difluoro-1,3-propanediol, tetrafluoro-1,4-butanediol, hexafluoro-1,5-pentanediol, octafluoro-1,6-hexanediol, dodecafluoro-1,8-octanediol, perfluoro-1,9-nonanediol, and perfluoro-1,10-decanediol.

[0039] In the present invention, the number-average molecular weight (Mn) of the polyether diol is preferably 500 to 3000 g / mol, such as 500 g / mol, 800 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, or any value therebetween. At this time, it is more beneficial to adjust the viscosity of the polyurethane system and enhance the compatibility of the polyphenylene ether diol and the fluorinated diol in the polyurethane system. The polyether diol can be a conventional choice for preparing polyurethane adhesives in the prior art.

[0040] In the present invention, the polyisocyanate can be an aliphatic diisocyanate and / or an aromatic diisocyanate, and specific examples thereof include, but are not limited to, at least one of 1,5-naphthalene diisocyanate (NDI), 4,4'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate (MDI), hydrogenated diphenylmethane diisocyanate (HMDI), toluene diisocyanate isomers (TDI), isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate (TMXDI).

[0041] In the present invention, the polymerization reaction of the polyol and the polyisocyanate preferably includes: performing a first polymerization reaction on the polyphenylene ether diol and the fluorinated diol in the presence of a first catalyst to obtain a diol prepolymer; and then performing a second polymerization reaction on the diol prepolymer, the polyether diol, and the polyisocyanate in the presence of a second catalyst to obtain an isocyanate-terminated polyurethane prepolymer. At this time, first polymerizing to obtain the diol prepolymer and then polymerizing with the polyisocyanate is more beneficial to improving the compatibility of the fluorocarbon chain with the polyurethane system, enhancing the protective effect of fluorine atoms on the molecular chain, and improving the stability and hydrophobicity of the molecular chain, thereby improving the high-temperature and high-humidity aging resistance of the polyurethane adhesive. In addition, the obtained diol prepolymer can be a homopolymer, copolymer, or block polymer of the polyphenylene ether diol and the fluorinated diol.

[0042] In the present invention, the molar ratio of the hydroxyl groups of the diol prepolymer and the polyether diol to the isocyanate groups of the polyisocyanate is preferably 1:(1.1 - 1.5), such as 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or any value therebetween. The molar ratio of the hydroxyl groups of the diol prepolymer and the polyether diol is preferably 1:(1 - 3), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3 or any value therebetween.

[0043] In the present invention, the molar ratio of the polyphenylene ether diol to the fluorinated diol is preferably 1:(2 - 6), such as 1:2, 1:3, 1:4, 1:5, 1:6 or any value therebetween.

[0044] In the present invention, the dosage of the first catalyst is preferably 0.01 - 0.1 wt% of the total mass of the polyphenylene ether diol and the fluorinated diol, such as 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt% or any value therebetween. The first catalyst can be any compound that can catalyze the first polymerization reaction of the hydroxyl groups in the polyphenylene ether diol and the fluorinated diol, and is preferably a titanate catalyst. Specific examples thereof include, but are not limited to, at least one of isopropyl titanate, n-butyl titanate, and isobutyl titanate.

[0045] In the present invention, the dosage of the second catalyst is preferably 0.05 - 0.5 wt% of the mass of the polyisocyanate, such as 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt% or any value therebetween. The first catalyst can be any compound that can catalyze the second polymerization reaction of the hydroxyl groups of the diol prepolymer and the isocyanate groups of the polyisocyanate, and is preferably a tin-based catalyst and / or an amine catalyst. Specific examples thereof include, but are not limited to, at least one of dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dimethyltin dinovate, stannous octoate, triethylamine, and N-methyldiethanolamine.

[0046] In the present invention, the conditions of the first polymerization reaction preferably include: the temperature is 70 - 90 °C, such as 70 °C, 75 °C, 80 °C, 85 °C, 90 °C or any value therebetween; the time is 12 - 24 h, such as 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h or any value therebetween.

[0047] In the present invention, the conditions of the second polymerization reaction preferably include: the temperature is 40 - 80 °C, such as 40 °C, 50 °C, 60 °C, 70 °C, 80 °C or any value therebetween; the time is 2 - 6 h, such as 2 h, 3 h, 4 h, 5 h, 6 h or any value therebetween.

[0048] In the present invention, the aromatic diol is preferably bisphenol A and / or bisphenol F.

[0049] In the present invention, the siloxane functionality of the unmodified silane coupling agent is preferably 3 to 4.

[0050] In the present invention, the unmodified silane coupling agent is preferably selected from at least one of amino silanes, mercapto silanes, and epoxy silanes, and specific examples thereof include but are not limited to: 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane. The unmodified silane coupling agent is more preferably an amino silane.

[0051] In the present invention, the molar ratio of the aromatic diol to the unmodified silane coupling agent is preferably 1:(1.2 to 1.5), such as 1:1.2, 1:1.3, 1:1.4, 1:1.5, or any value therebetween. At this time, it is more beneficial to inhibit the self-polymerization of the silane coupling agent.

[0052] In the present invention, the modification reaction is preferably carried out in the presence of an acidic catalyst. The acidic catalyst is preferably selected from at least one of hydrochloric acid, nitric acid, acetic acid, and formic acid.

[0053] In the present invention, the conditions of the modification reaction preferably include: the temperature is 30 to 50 °C, such as 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, or any value therebetween; the time is 2 to 6 h, such as 2 h, 3 h, 4 h, 5 h, 6 h, or any value therebetween; the pH is 4 to 6, such as 4, 4.5, 5, 5.5, 6, or any value therebetween. When the temperature, time, and pH of the modification reaction are controlled within the above preferred ranges, it is more beneficial to the hydrolysis of the unmodified silane coupling agent and the condensation modification reaction with the aromatic diol, and at the same time, it can also inhibit the self-polymerization reaction of the silane coupling agent and avoid introducing organopolysiloxane compounds.

[0054] In the present invention, the auxiliary agent can be an auxiliary agent commonly used in existing polyurethane adhesives, preferably selected from at least one of a water scavenger, a rheology modifier, a leveling agent, a filler, an antifoaming agent, a diluent, and a bonding promoter, and more preferably at least one of a water scavenger, a rheology modifier, and a diluent.

[0055] In addition, the terms "first" and "second" are only for the purpose of convenient description and should not be construed as a special limitation on the type or quantity of technical features.

[0056] The present invention will be described in detail below through specific examples. The examples are intended to explain the present invention and should not be construed as a limitation on the present invention. For those not specifying specific techniques or conditions in the examples, the techniques or conditions described in the literature in the field or according to the product specifications are followed. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0057] Synthesis Example 1 Synthesis of Polyphenylene Ether Diol B1

[0058] 1) Add 200 g of 2,6-dimethylphenol, 57.00 g of bisphenol A, 780.00 g of toluene, and 114.00 g of methanol to a reaction kettle equipped with a condensation reflux device. After stirring until all the monomers are dissolved, add 16.50 g of a dodecyl polyethyleneimine ligand (Mn = 2000 mol / L) and 6.17 g of a hydrobromic acid solution of cuprous bromide (freshly prepared with 0.45 g of cuprous oxide and 5.72 g of 48% hydrobromic acid), mix evenly, introduce oxygen (flow rate: 200 sccm), and react at 40 °C for 2 h;

[0059] 2) Add the reacted polymer solution to 50 mL of a 10% sodium nitrilotriacetate solution, react at 70 °C for 1 h, and then centrifuge to remove the aqueous phase.

[0060] 3) Concentrate the oily phase obtained by centrifugation in step 2) to about 900 mL, add 9000 mL of methanol to precipitate, filter, wash with methanol three times, and dry under vacuum at 80 °C overnight to obtain polyphenylene ether diol B1, Mn = 720 g / mol. By nuclear magnetic resonance detection, polyphenylene ether diol B1 has the structure shown in formula (1), where R1 to R4 are all hydrogen atoms and X is -O-.

[0061] Synthesis Example 2 Synthesis of Polyphenylene Ether Diol B2

[0062] 1) Add 280 g of 2,6-dimethylphenol, 47.00 g of 2,2',4,4'-tetramethylbisphenol A, 950.00 g of toluene, and 94.00 g of methanol into a reaction kettle equipped with a condensation reflux device. After stirring until all the monomers are dissolved, add 12.50 g of dodecyl polyethyleneimine ligand (Mn = 600 mol / L) and a hydrobromic acid solution of 6.17 g of cuprous bromide (freshly prepared with 0.45 g of cuprous oxide and 5.72 g of 48% hydrobromic acid). Mix evenly, introduce oxygen (flow rate: 200 sccm), and react at 50 °C for 3 h.

[0063] 2) Add the reacted polymer solution into 50 mL of 10% sodium nitrilotriacetate solution, react at 70 °C for 1 h, and then centrifuge to remove the aqueous phase.

[0064] 3) Concentrate the oil phase obtained by centrifugation in step 2) to about 900 mL, add 9000 mL of methanol for precipitation, filter, wash with methanol three times, and dry overnight in a vacuum at 80 °C to obtain polyphenylene ether diol B2, Mn = 1450 g / mol. By nuclear magnetic resonance detection, polyphenylene ether diol B2 has the structure shown in formula (1), where R1 to R4 are all hydrogen atoms, and X is -C(CH3)2-.

[0065] Preparation Example 1 Preparation of Isocyanate-Terminated Polyurethane Prepolymer P1

[0066] Weigh polyphenylene ether diol B1 and tetrafluoro-1,4-butanediol according to a molar ratio of hydroxyl groups of 1:4. First, mix polyphenylene ether diol B1 with N,N-dimethylformamide, stir to dissolve, introduce nitrogen, then add tetrafluoro-1,4-butanediol and isopropyl titanate (the dosage is 0.05 wt% of the total mass of polyphenylene ether diol B1 and tetrafluoro-1,4-butanediol), stir and react at 80 °C for 12 h, then evaporate the solvent, cool down and discharge to obtain a diol prepolymer. After testing, its hydroxyl value is about 86 mg KOH / g. First, vacuum dehydrate the above-obtained diol prepolymer and poly(1,4-butanediol) (Mn = 1000 g / mol, purchased from Merck reagent) at 100 °C for 1 h. Then, weigh the diol prepolymer, poly(1,4-butanediol), and 4,4'-diphenylmethane diisocyanate according to a molar ratio of hydroxyl groups of the diol prepolymer, hydroxyl groups of poly(1,4-butanediol), and isocyanate groups of 1:1:2.6. Mix the three and add dibutyltin dilaurate (the dosage is 0.1 wt% of the mass of 4,4'-diphenylmethane diisocyanate), stir and react at 60 °C for 4 h, then cool down and discharge. The obtained reaction product is isocyanate-terminated polyurethane prepolymer P1.

[0067] Preparation Example 2 Preparation of Isocyanate-Terminated Polyurethane Prepolymer P2

[0068] Weigh polyphenylene ether diol B1 and tetrafluoro-1,4-butanediol according to the molar ratio of hydroxyl groups of 1:6. First, mix polyphenylene ether diol B1 with N,N-dimethylformamide, stir to dissolve, introduce nitrogen, then add tetrafluoro-1,4-butanediol and isopropyl titanate (the dosage is 0.05 wt% of the total mass of polyphenylene ether diol B1 and difluoro-1,3-propanediol). After stirring and reacting at 80 °C for 12 h, evaporate the solvent, cool down and discharge to obtain the diol prepolymer. After testing, its hydroxyl value is about 70 mg KOH / g. First, vacuum dehydrate the above-obtained diol prepolymer and poly(1,4-butanediol) (Mn = 1000 g / mol, purchased from Merck reagent) at 100 °C for 1 h. Then, weigh the diol prepolymer, poly(1,4-butanediol) and 1,6-hexamethylene diisocyanate according to the molar ratio of the hydroxyl groups of the diol prepolymer, the hydroxyl groups of poly(1,4-butanediol) and isocyanate groups of 1:2:4.5. Mix the three and add dibutyltin dilaurate (the dosage is 0.1 wt% of the mass of 1,6-hexamethylene diisocyanate). After stirring and reacting at 60 °C for 4 h, cool down and discharge. The obtained reaction product is the isocyanate-terminated polyurethane prepolymer P2.

[0069] Preparation Example 3 Preparation of Isocyanate-Terminated Polyurethane Prepolymer P3

[0070] Weigh polyphenylene ether diol B2 and difluoro-1,3-propanediol according to the molar ratio of hydroxyl groups of 1:2. First, mix polyphenylene ether diol B1 with N,N-dimethylformamide, stir to dissolve, introduce nitrogen, then add tetrafluoro-1,4-butanediol and isopropyl titanate (the dosage is 0.05 wt% of the total mass of polyphenylene ether diol B2 and difluoro-1,3-propanediol). After stirring and reacting at 80 °C for 12 h, evaporate the solvent, cool down and discharge to obtain the diol prepolymer. After testing, its hydroxyl value is about 68 mg KOH / g. First, vacuum dehydrate the above-obtained diol prepolymer and poly(1,4-butanediol) (Mn = 1000 g / mol, purchased from Merck reagent) at 100 °C for 1 h. Then, weigh the diol prepolymer, poly(1,4-butanediol) and 1,5-naphthalene diisocyanate according to the molar ratio of the hydroxyl groups of the diol prepolymer, the hydroxyl groups of poly(1,4-butanediol) and isocyanate groups of 1:3:4.4. Mix the three and add dibutyltin dilaurate (the dosage is 0.1 wt% of the mass of 1,5-naphthalene diisocyanate). After stirring and reacting at 60 °C for 4 h, cool down and discharge. The obtained reaction product is the isocyanate-terminated polyurethane prepolymer P3.

[0071] Preparation Example 4 Preparation of Isocyanate-Terminated Polyurethane Prepolymer P4

[0072] Weigh polyphenylene ether diol B1, tetrafluoro-1,4-butanediol, and 4,4'-diphenylmethane diisocyanate according to the molar ratio of hydroxyl group:hydroxyl group:isocyanate group of 1:4:5:13. First, vacuum dehydrate polyphenylene ether diol B1 and tetrafluoro-1,4-butanediol at 100 °C for 1 h. Then, mix the vacuum-dehydrated polyphenylene ether diol B1 and tetrafluoro-1,4-butanediol with 4,4'-diphenylmethane diisocyanate and dibutyltin dilaurate (the dosage is 0.1 wt% of the mass of 4,4'-diphenylmethane diisocyanate), and stir and react at 60 °C for 6 h. After cooling, discharge the material, and the obtained reaction product is the isocyanate-terminated polyurethane prepolymer P4.

[0073] Preparation Example 5 Preparation of Modified Silane Coupling Agent S1

[0074] Weigh bisphenol A and 3-aminopropyltriethoxysilane according to the molar ratio of 1:1.2, prepare a mixed solution of methanol and deionized water according to the volume ratio of 2:1, add the weighed bisphenol A and 3-aminopropyltriethoxysilane to the mixed solution, and adjust the pH of the reaction system to 5 by dropping nitric acid solution. Then, raise the temperature to 40 °C and stir and react for 4 h. The reaction product obtained after evaporating the solvent is the modified silane coupling agent S1.

[0075] Preparation Example 6 Preparation of Modified Silane Coupling Agent S2

[0076] Weigh bisphenol F and 3-aminopropyltriethoxysilane according to the molar ratio of 1:1.5, prepare a mixed solution of methanol and deionized water according to the volume ratio of 2:1, add the weighed bisphenol A and 3-aminopropyltriethoxysilane to the mixed solution, and adjust the pH of the reaction system to 5 by dropping nitric acid solution. Then, raise the temperature to 40 °C and stir and react for 4 h. The reaction product obtained after evaporating the solvent is the modified silane coupling agent S2.

[0077] Example 1 Preparation of Polyurethane Adhesive

[0078] Add 100 parts by weight of the isocyanate-terminated polyurethane prepolymer P1 prepared in Preparation Example 1, 8 parts by weight of the modified silane coupling agent S1 prepared in Preparation Example 5, 2 parts by weight of a water scavenger (molecular sieve water absorbent, purchased from Arkema company, brand Siliporite SA1702), and 1 part by weight of fumed silica (purchased from Cabot company, brand TS-720) to a mixing tank, mix under vacuum conditions (vacuum degree is 980 mbar), first mix at a speed of 2000 r / min for 10 min, then scrape the raw materials on the wall of the mixing tank into the system with a spatula, and continue to mix at a speed of 2000 r / min for 5 min. After discharging, store it in a sealed manner to obtain the polyurethane adhesive.

[0079] Preparation of Polyurethane Adhesive in Example 2

[0080] 100 parts by weight of the isocyanate-terminated polyurethane prepolymer P2 prepared in Preparation Example 2, 5 parts by weight of the modified silane coupling agent S2 prepared in Preparation Example 6, 2 parts by weight of a water scavenger (purchased from Borchers GmbH, Germany, product number Additive TI), and 1 part by weight of fumed silica (purchased from CABOT Corporation, product number TS-720) were added to a mixing tank and mixed under vacuum conditions (vacuum degree: 980 mbar). First, the mixture was mixed at a speed of 2000 r / min for 10 min, then the raw materials on the wall of the mixing tank were scraped into the system with a spatula, and the mixture was continuously mixed at a speed of 2000 r / min for 5 min. After discharging, it was stored in a sealed manner to obtain the polyurethane adhesive.

[0081] Preparation of Polyurethane Adhesive in Example 3

[0082] 100 parts by weight of the isocyanate-terminated polyurethane prepolymer P3 prepared in Preparation Example 3, 10 parts by weight of the modified silane coupling agent S2 prepared in Preparation Example 6, 2 parts by weight of a water scavenger (purchased from Borchers GmbH, Germany, product number Additive OF), and 1 part by weight of fumed silica (purchased from CABOT Corporation, product number TS-720) were added to a mixing tank and mixed under vacuum conditions (vacuum degree: 980 mbar). First, the mixture was mixed at a speed of 2000 r / min for 10 min, then the raw materials on the wall of the mixing tank were scraped into the system with a spatula, and the mixture was continuously mixed at a speed of 2000 r / min for 5 min. After discharging, it was stored in a sealed manner to obtain the polyurethane adhesive.

[0083] Preparation of Polyurethane Adhesive in Example 4

[0084] The polyurethane adhesive was prepared according to the method of Example 1, except that the isocyanate-terminated polyurethane prepolymer P4 prepared in Preparation Example 4 with the same mass was used to replace the isocyanate-terminated polyurethane prepolymer P1 prepared in Preparation Example 1, and the other conditions were the same as those in Example 1. Thus, the polyurethane adhesive was prepared.

[0085] Preparation of Reference Polyurethane Adhesive in Comparative Example 1

[0086] Polyphenylene ether diol B1 and 4,4'-diphenylmethane diisocyanate were weighed according to the molar ratio of hydroxyl group:isocyanate group of 1:1.3, and dibutyltin dilaurate (the dosage was 0.1 wt% of the mass of 4,4'-diphenylmethane diisocyanate) was added. After stirring and reacting at 60 °C for 4 h, the solvent was removed by a vacuum water pump, and the resulting reaction product was the isocyanate-terminated polyurethane prepolymer DP1.

[0087] The reference polyurethane adhesive was prepared according to the method of Example 1, except that the isocyanate-terminated polyurethane prepolymer DP1 with the same mass was used instead of the isocyanate-terminated polyurethane prepolymer P1 in Preparation Example 1, and the remaining conditions were the same as those in Example 1, and thus the reference polyurethane adhesive was prepared.

[0088] Preparation of Reference Polyurethane Adhesive in Comparative Example 2

[0089] Tetrafluoro-1,4-butanediol and 4,4'-diphenylmethane diisocyanate were weighed according to the molar ratio of hydroxyl group:isocyanate group of 1:1.3, and dibutyltin dilaurate (the dosage was 0.1 wt% of the mass of 4,4'-diphenylmethane diisocyanate) was added. After stirring and reacting at 60 °C for 4 h, the solvent was removed by a vacuum water pump, and the resulting reaction product was the isocyanate-terminated polyurethane prepolymer DP2.

[0090] The reference polyurethane adhesive was prepared according to the method of Example 1, except that the isocyanate-terminated polyurethane prepolymer DP2 with the same mass was used instead of the isocyanate-terminated polyurethane prepolymer P1 in Preparation Example 1, and the remaining conditions were the same as those in Example 1, and thus the reference polyurethane adhesive was prepared.

[0091] Preparation of Reference Polyurethane Adhesive in Comparative Example 3

[0092] The reference polyurethane adhesive was prepared according to the method of Example 1, except that the same mass of 3-aminopropyltriethoxysilane was used instead of the modified silane coupling agent S1 in Preparation Example 5, and the remaining conditions were the same as those in Example 1, and thus the reference polyurethane adhesive was prepared.

[0093] Test Example

[0094] The polyurethane adhesives prepared in the above examples and comparative examples were tested for the bonding strength performance and aging resistance according to the following method, and the results are shown in Table 1.

[0095] (1) Bonding performance test before aging: The specimen was a butt joint structure, and the substrate was PC-printed glass. Prepare a thrust test specimen. After two thrust pieces were butted, the polyurethane adhesives obtained in each example and comparative example were used for bonding. A square glue line was coated, the glue line was 17 mm * 4 in length, 1 mm in width, and the glue layer thickness was controlled at 0.15 mm. After curing at 23 ± 2 °C and a humidity of 50 ± 5% for 48 h, the fabricated bonded specimen was run along the shear direction at a speed of 10 mm / min by a universal material testing machine until the specimen bonding failed, and the maximum force value displayed by the instrument was recorded. The shear bonding strength of the adhesive to the stainless steel substrate after 48 h of curing was calculated in combination with the bonding area.

[0096] (2) High-temperature and high-humidity resistance performance test: The PC-ink glass bonding sample cured by the method in (1) is aged for 360 h under the conditions of 85°C / 85% RH. After aging, it is cooled to room temperature and then the shear bonding strength is measured to determine the shear strength (MPa) after aging at 85°C / 85% RH.

[0097] (3) Resistance to artificial sweat performance: According to the method in the GB / T 9274 standard, the PC-ink glass bonding sample cured by the method in (1) is immersed in artificial sweat, and the soaking time is recorded when the bonding fails. (Artificial sweat formula: sodium chloride 20 g / L, ammonium chloride 17.5 g / L, urea 5 g / L, acetic acid 2.5 g / L, lactic acid, and then sodium hydroxide NaOH is added until the pH value of the solution reaches 4.7)

[0098] Table 1

[0099]

[0100] As can be seen from the results in Table 1, compared with Comparative Examples 1-3, the polyurethane adhesive provided by the embodiments of the present invention has higher bonding strength performance, can still maintain a relatively high bonding strength after aging at 85°C / 85% RH, can withstand artificial sweat corrosion for a longer time, and has good aging resistance.

[0101] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principle and purpose of the present invention.

Claims

1. A polyurethane adhesive, characterized in that: The polyurethane adhesive comprises: an isocyanate-terminated polyurethane prepolymer, a modified silane coupling agent and an optional auxiliary agent; the isocyanate-terminated polyurethane prepolymer is obtained by polymerization reaction of polyol and polyisocyanate, wherein the polyol at least comprises polyphenylene ether diol, fluorine-containing diol and polyether diol; the modified silane coupling agent is obtained by modification reaction of aromatic diol and unmodified silane coupling agent.

2. The polyurethane adhesive according to claim 1, characterized in that: The mass ratio of the isocyanate-terminated polyurethane prepolymer to the modified silane coupling agent and the auxiliary agent is 100:(5-10):(0-10); Preferably, the molar ratio of the hydroxyl group of the polyol to the isocyanate group of the polyisocyanate is 1:(1.1-1.5).

3. The polyurethane adhesive according to claim 1, characterized in that: The number average molecular weight of the polyphenylene ether diol is 500 to 2000 g / mol; Preferably, the fluorinated diol is selected from at least one of difluoro-1,3-propylene glycol, tetrafluoro-1,4-butanediol, hexafluoro-1,5-pentanediol, octafluoro-1,6-hexanediol, dodecafluoro-1,8-octanediol, perfluoro-1,9-nonanediol, and perfluoro-1,10-decanediol. Preferably, the number average molecular weight of the polyether diol is 500 to 3000 g / mol; Preferably, the polyisocyanate is an aliphatic diisocyanate and / or an aromatic diisocyanate.

4. The polyurethane adhesive according to claim 1, characterized in that: The polymerization reaction of the polyol and the polyisocyanate comprises: subjecting the polyphenylene ether diol and the fluorine-containing diol to a first polymerization reaction in the presence of a first catalyst to obtain a diol prepolymer; and subjecting the diol prepolymer, the polyether diol and the polyisocyanate to a second polymerization reaction in the presence of a second catalyst to obtain an isocyanate-terminated polyurethane prepolymer.

5. The polyurethane adhesive according to claim 4, characterized in that: The molar ratio of the hydroxyl group of the diol prepolymer and the polyether diol to the isocyanate group of the polyisocyanate is 1:(1.1-1.5); Preferably, the molar ratio of the polyphenylene ether diol to the fluorine-containing diol is 1:(2-6); Preferably, the amount of the first catalyst is 0.01 to 0.1 wt % of the total mass of the polyphenylene ether diol and the fluorine-containing diol; Preferably, the second catalyst is used in an amount of 0.05 to 0.5 wt % of the mass of the polyisocyanate.

6. The polyurethane adhesive according to claim 4, characterized in that: The first catalyst is a titanate catalyst; Preferably, the second catalyst is a tin-based catalyst and / or an amine catalyst; Preferably, the conditions of the first polymerization reaction include: temperature of 70 to 90° C., time of 12 to 24 h; Preferably, the conditions of the second polymerization reaction include: temperature of 40 to 80° C. and time of 2 to 6 hours.

7. The polyurethane adhesive according to claim 1, characterized in that: The aromatic diol is bisphenol A and / or bisphenol F; Preferably, the siloxane functionality of the unmodified silane coupling agent is 3 to 4; Preferably, the unmodified silane coupling agent is selected from at least one of aminosilane, mercaptosilane and epoxysilane; Preferably, the molar ratio of the aromatic diol to the unmodified silane coupling agent is 1:(1.2-1.5); Preferably, the modification reaction is carried out in the presence of an acidic catalyst; Preferably, the modification reaction conditions include: temperature of 30-50° C., time of 2-6 h, and pH of 4-6.

8. The polyurethane adhesive according to claim 1, characterized in that: The auxiliary agent is selected from at least one of a dewatering agent, a rheological agent, a leveling agent, a filler, a defoaming agent, a diluent, and an adhesion promoter.

9. The method for preparing the polyurethane adhesive according to any one of claims 1 to 8, characterized in that: The preparation method comprises: mixing polyphenylene ether diol, fluorine-containing diol and polyisocyanate to obtain isocyanate-terminated polyurethane prepolymer after polymerization reaction, and then mixing the isocyanate-terminated polyurethane prepolymer, modified silane coupling agent and optional auxiliary agent to obtain a product which is a polyurethane adhesive.

10. Use of the polyurethane adhesive according to any one of claims 1 to 8 in bonding electronic products.

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