Furyl polyurethane adhesive and synthesis method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a furyl polyurethane adhesive and a synthesis method thereof, polymer polyol is used as a soft segment, isocyanate and two specific furyl chain extenders are used as hard segments, polymerization is performed through a one-step method, and the method has the advantages of simple process, short flow, mild reaction conditions and the like. Wherein a furan ring and an amide group of the two specific furyl chain extenders endow the material with rigidity and excellent bonding performance, and form a high-density hydrogen bond network with a hydrazide group, so that the mechanical strength, the toughness and the bonding performance of the material are remarkably improved. By regulating and controlling the proportion of the components, the rigidity and flexibility of the material can be effectively balanced, so that the polyurethane adhesive with excellent comprehensive performance is prepared. The furyl polyurethane adhesive prepared by the invention has relatively high adhesion strength and mechanical strength, and can be applied to the fields of buildings, automobile manufacturing, medical treatment, packaging, aerospace, electronics and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a furan-based polyurethane adhesive and its synthesis method. Background Technology

[0002] Polyurethane (PU), an important polymer material, is hailed as the "fifth largest plastic." It can be synthesized from isocyanates, polyols, and chain extenders, and its properties can be controlled through structural design. It possesses excellent mechanical properties, abrasion resistance, chemical resistance, low-temperature flexibility, biocompatibility, and processability, making it widely applicable in elastomers, coatings, foams, and adhesives, thus demonstrating broad application and development prospects. However, traditional polyurethane materials heavily rely on petroleum-based raw materials. Developing high-performance polyurethanes based on biomass raw materials has become an important development direction and urgent need in this field.

[0003] Currently, most of the raw materials required for the industrial production of polyurethane (PU), such as isocyanates and polyols, still come from petrochemical resources. To achieve green and sustainable development of PU and overcome dependence on petroleum-based raw materials, researchers are dedicated to finding suitable green and renewable biomass resources for the synthesis of biomass PU materials. In recent years, bio-based new materials have attracted considerable attention in the synthesis of polyurethane due to their low toxicity, thermal stability, low cost, and biodegradability.

[0004] Publication number CN118580453A discloses a furan ring-based polyurethane, a polyurethane emulsion, its preparation method and application. A furan ring-based polyurethane is obtained by polymerization reaction using furan-based diol compounds and diisocyanates as raw materials. The polyurethane material has certain rigidity, biodegradability and environmental friendliness. However, the method does not explore the bonding performance and is only applied in the agricultural field. CN116333665B discloses a thermoplastic polyurethane hot melt adhesive and its preparation method. The hot melt adhesive is prepared using N,N-bis(2-hydroxyethyl)-2,5-furandicarboxylic acid (FDCA)-derived N,N-bis(2-hydroxyethyl)-2,5-furandicarboxamide (HO-FDAM-OH) as a chain extender, polymeric diol, and isocyanate as raw materials. This method introduces furanamide groups, which possess both rigid structure and hydrogen bonding interactions, into the hard segments of the polyurethane. The hot melt adhesive can form various non-covalent interactions with metal atoms, ions, and polar groups on the substrate surface through the amide groups and oxygen atoms on the furan ring, exhibiting excellent comprehensive adhesive properties, including good initial and final bond strength, and repeatable adhesion. This reaction requires a chain extension reaction in a prepolymer mixture at 90–120°C for 18–30 hours, resulting in high reaction temperature, long reaction time, and high energy consumption.

[0005] Therefore, given the shortcomings of existing furan-based polyurethane adhesives, such as complex synthesis processes and poor performance, solving the problem of how to prepare furan-based polyurethane adhesives with high strength, high toughness, and high adhesion is a pressing technical issue for the polyurethane adhesive industry. Summary of the Invention

[0006] The purpose of this invention is to provide a furan-based polyurethane adhesive and its synthesis method. This method has the advantages of simple process, short process, mild reaction conditions, and the synthesized furan-based polyurethane adhesive has high strength, high toughness and high adhesion, thereby solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for synthesizing a furan-based polyurethane adhesive, comprising the following steps:

[0008] S1. Add the polymer polyol and antioxidant to a dry three-necked flask, and evacuate at 120-140°C for 2-3 hours to obtain the reaction solution.

[0009] S2. Cool the reaction solution to 70-90°C and backfill with nitrogen gas. Under nitrogen atmosphere, add isocyanate and catalyst, and stir for 2-3 hours to obtain the prepolymer.

[0010] S3. Add chain extender 1 and silane coupling agent to the prepolymer and stir to polymerize for 1-2 hours.

[0011] S4. After cooling the reaction temperature to 40-50℃, add chain extender II, add solvent to the reaction system, adjust the viscosity of the reaction system, continue polymerization for 6-12 hours, stop the reaction, dry and remove solvent to obtain furan-based polyurethane adhesive.

[0012] As a preferred embodiment of the present invention, the polymer polyol is polytetrahydrofurandiol (PTMG-1000); the first chain extender is N,N-bis(2-hydroxyethyl)-2,5-furandicarboxamide (HO-FDAM-OH); the second chain extender is 2,5-furandicarboxylhydrazine (FDHA); and the isocyanate is isophorone diisocyanate (IPDI).

[0013] As a preferred embodiment of the present invention, the structural formula of the furan-based polyurethane is as follows:

[0014]

[0015] As a preferred embodiment of the present invention, the molar ratio of chain extender one to chain extender two is 1:0.2 to 2.

[0016] As a preferred embodiment of the present invention, the ratio of the amount of the polymer polyol to the sum of the amounts of chain extender one and chain extender two is 1:0.5 to 2.

[0017] As a preferred embodiment of the present invention, the ratio of the amount of isocyanate to the sum of the amounts of polymer polyol, chain extender one, and chain extender two is 1:1.

[0018] As a preferred embodiment of the present invention, the antioxidant is a hindered phenolic antioxidant, including at least one of antioxidant 1010, antioxidant 1076, antioxidant 1135, antioxidant 264, and antioxidant 330.

[0019] As a preferred embodiment of the present invention, the antioxidant is 0.1 to 0.3% of the total mass of the four substances: polymer polyol, chain extender one, chain extender two, and isocyanate.

[0020] As a preferred embodiment of the present invention, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane (KH-550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602).

[0021] As a preferred embodiment of the present invention, the mass of the silane coupling agent is 0.5 to 2% of the total mass of the four substances: polymer polyol, chain extender one, chain extender two, and isocyanate.

[0022] As a preferred embodiment of the present invention, the catalyst is at least one of dibutyltin dilaurate (DBTDL), stannous oxalate, stannous octanoate, dibutyltin maleate, dibutyltin oxide, and monobutyltin oxide.

[0023] As a preferred embodiment of the present invention, the mass of the catalyst is 0.01 to 0.1% of the total mass of the four substances: polymer polyol, chain extender one, chain extender two, and isocyanate.

[0024] As a preferred embodiment of the present invention, the solvent is at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); the solvent is added to adjust the viscosity of the reaction system to 10-30 Pa·s.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention uses HO-FDAM-OH and FDHA, downstream materials derived from the biomass platform molecule FDCA, as chain extenders to construct furan-based polyurethane adhesive materials. HO-FDAM-OH and FDHA, as green raw materials, give it unique advantages in the field of sustainable polyurethane development.

[0027] 2. The two chain extenders introduced in this invention have highly rigid structures. They react with isocyanate groups to form hard segments of polyurethane. By adjusting the ratio of the two chain extenders and polymer diol, the flexibility, rigidity and adhesion of the material can be balanced, thereby preparing a polyurethane material with excellent comprehensive performance, effectively expanding the application range of furan bio-based platform molecules in the field of polyurethane adhesives.

[0028] 3. This invention uses furanylamide and furanylhydrazine chain extenders, resulting in polyurethane structures containing amide and hydrazine groups. The hydrazine groups can form a high-density hydrogen bond network, which is beneficial for improving the mechanical properties of the material, such as tensile strength and toughness, while also providing high hydrolysis resistance. The amide groups and oxygen atoms on the furan ring can interact with hydroxyl groups or polar functional groups on the matrix, which is beneficial for improving the adhesion properties of the polyurethane material. This invention provides a new approach for developing polyurethane materials with high strength, high toughness, and high adhesion.

[0029] 4. The synthesis method for preparing furan-based polyurethane adhesive materials according to the present invention is simple, has a short process, and mild reaction conditions. The prepared furan-based polyurethane adhesive materials have high adhesion strength and mechanical strength, and can be applied in fields such as construction, automobile manufacturing, medical, packaging, aerospace, and electronics, and have great application potential. Attached Figure Description

[0030] Figure 1 This is the structural formula of the furan-based polyurethane of the present invention.

[0031] Figure 2 This is the Fourier transform infrared (FT-IR) spectrum of furan-based polyurethane in Embodiment 1 of the present invention.

[0032] Figure 3 This is the 1H NMR spectrum of furan-based polyurethane in Example 1 of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Polyurethane (PU) is a block copolymer with alternating soft and hard structures. The soft segments are derived from polyester or polyether-based polyols, while the hard segments are formed by the reaction between isocyanates and chain extenders. The hard segments largely determine the molecular chain interactions and network structure of polyurethane. Due to the high rigidity and polarity of the hard segments and the flexibility and non-polarity of the soft segments, this difference in hard and soft polarity leads to the formation of phase separation morphologies in PU. By controlling the ratio of polymeric polyols to chain extenders, PU can be endowed with a unique soft-hard block structure and microphase separation characteristics, thereby obtaining ideal mechanical properties. Furthermore, introducing dynamic covalent or non-covalent interactions between polymer chains or between polymer chains and the substrate surface is an effective strategy to improve adhesion strength.

[0035] This invention provides a method for synthesizing furan-based polyurethane adhesives, the specific steps of which are as follows:

[0036] S1. Add the polymer polyol (polytetrahydrofurandiol) and antioxidant to a dry three-necked flask, and evacuate at 120-140°C for 2-3 hours to obtain the reaction solution.

[0037] S2. Cool the reaction solution to 70-90℃ and backfill with nitrogen gas. Under nitrogen atmosphere, add isocyanate (isophorone diisocyanate) and catalyst, and stir the reaction for 2-3 hours to obtain the prepolymer.

[0038] S3. Add chain extender (N,N-bis(2-hydroxyethyl)-2,5-furandicarboxamide) and silane coupling agent to the prepolymer, and stir to polymerize for 1-2 hours.

[0039] S4. After cooling the reaction temperature to 40-50℃, add chain extender di(2,5-furandicarboxyhydrazide), add solvent to the reaction system to adjust the viscosity of the reaction system, continue polymerization for 6-12 hours, stop the reaction, dry and remove solvent to obtain furan-based polyurethane adhesive.

[0040] The structure of the furan-based polyurethane adhesive synthesized in this invention is as follows: Figure 1 As shown.

[0041] Example 1:

[0042] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0043] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 17mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0044] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (4.44g, 20.0mmol) and 10mg DBTDL. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0045] S3. Add chain extender HO-FDAM-OH (1.21g, 5.0mmol) and 0.17g silane coupling agent KH560 to the prepolymer and stir to polymerize for 1h.

[0046] S4. After cooling the reaction temperature to 50℃, add 30 mL of LDMF and chain extender FDHA (0.92 g, 5.0 mmol). Continue polymerization for 6 hours, then stop the reaction. Dry and remove solvent to obtain a light yellow solid product, namely furan-based polyurethane adhesive. The molecular weight was measured to be 44570 g / mol, and the intrinsic viscosity was 0.82 dL / g.

[0047] The Fourier transform infrared (FT-IR) spectrum of the furan-based polyurethane adhesive obtained in this embodiment is shown below. Figure 2 As shown, FT-IR characterization analysis revealed that the characteristic peaks corresponding to the stretching vibrations of COC, CH, and C=C on the furan ring appeared at 1075 cm⁻¹. -1 2925cm -1 and 1586cm -1 The C=O stretching vibration peak of carbamate appears at 1654 cm⁻¹. -1 At this point, the NH bending vibration peak appears at 1537 cm⁻¹. -1 The stretching vibration peak of the C=O group of the furan-dicarboxamide group is at 1637 cm⁻¹. -1 At 3300 cm⁻¹, the stretching vibration absorption peak of amide-NH appears. -1 2276cm -1 The absence of absorption peaks near isocyanate groups indicates complete IPDI conversion.

[0048] The 1H NMR spectrum of the furan-based polyurethane adhesive obtained in this embodiment is as follows: Figure 3 As shown, the polyurethane structure is correct.

[0049] Example 2:

[0050] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the vacuum temperature in S1 is replaced with 140℃, while the remaining components and methods are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 44573 g / mol, and the intrinsic viscosity was 0.82 dL / g.

[0051] Example 3:

[0052] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the vacuuming time in S1 is replaced with 3 hours; the remaining components and methods are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 44568 g / mol, and the intrinsic viscosity was 0.81 dL / g.

[0053] Example 4:

[0054] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the reaction temperature in step S2 is replaced with 90°C; the remaining components and methods are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 44650 g / mol, and the intrinsic viscosity was 0.83 dL / g.

[0055] Example 5:

[0056] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the reaction time S2 is replaced with 3 hours, while the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 43700 g / mol, and the intrinsic viscosity was 0.80 dL / g.

[0057] Example 6:

[0058] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the S2 reaction conditions are replaced by reacting at 70℃, 80℃, and 90℃ for one hour each; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 53100 g / mol, and the intrinsic viscosity was 0.90 dL / g.

[0059] Example 7:

[0060] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the S3 polymerization time is replaced with 2 hours; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 45,000 g / mol, and the intrinsic viscosity was 0.83 dL / g.

[0061] Example 8:

[0062] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the reaction temperature in step S4 is replaced with 40°C; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 39500 g / mol, and the intrinsic viscosity was 0.67 dL / g.

[0063] Example 9:

[0064] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the reaction time in step S4 is replaced with 9 hours; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 46330 g / mol, and the intrinsic viscosity was 0.85 dL / g.

[0065] Example 10:

[0066] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the reaction time in step S4 is replaced with 12 hours; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 58700 g / mol, and the intrinsic viscosity was 0.92 dL / g.

[0067] Example 11:

[0068] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the reaction solvent is replaced with DMAc; the remaining components and steps are the same as in Example 1. After the reaction is completed and the product is discharged, the molecular weight of the product is measured to be 44500 g / mol, and the intrinsic viscosity is 0.80 dL / g.

[0069] Example 12:

[0070] A method for synthesizing a furan-based polyurethane adhesive is as follows: compared with Example 1, only the reaction solvent is replaced with NMP, while the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 39580 g / mol, and the intrinsic viscosity was 0.66 dL / g.

[0071] Example 13:

[0072] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the catalyst is replaced with an equal mass of stannous oxalate; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 33450 g / mol, and the intrinsic viscosity was 0.63 dL / g.

[0073] Example 14:

[0074] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the catalyst is replaced with an equal mass of stannous octoate; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 39780 g / mol, and the intrinsic viscosity was 0.67 dL / g.

[0075] Example 15:

[0076] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only antioxidant 330 is replaced with an equal mass of antioxidant 1010, while the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 41700 g / mol, and the intrinsic viscosity was 0.69 dL / g.

[0077] Example 16:

[0078] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the silane coupling agent is replaced with an equal mass of KH-550, while the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 43650 g / mol, and the intrinsic viscosity was 0.80 dL / g.

[0079] Example 17:

[0080] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the mass of the catalyst DBTDL is replaced with 1.7 mg; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 31000 g / mol, and the intrinsic viscosity was 0.60 dL / g.

[0081] Example 18:

[0082] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the catalyst mass is replaced with 17 mg, while the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 46710 g / mol, and the intrinsic viscosity was 0.84 dL / g.

[0083] Example 19:

[0084] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the antioxidant 330 is replaced with 51 mg by mass; the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 45710 g / mol, and the intrinsic viscosity was 0.84 dL / g.

[0085] Example 20:

[0086] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the mass of the silane coupling agent KH560 is replaced with 0.083 g, while the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 39575 g / mol, and the intrinsic viscosity was 0.66 dL / g.

[0087] Example 21:

[0088] A method for synthesizing a furan-based polyurethane adhesive is as follows: Compared with Example 1, only the mass of the silane coupling agent KH560 is replaced with 0.33g, while the remaining components and steps are the same as in Example 1. After the reaction, the molecular weight of the product was measured to be 41500g / mol, and the intrinsic viscosity was 0.78dL / g.

[0089] Example 22:

[0090] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0091] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 20mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0092] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (6.66g, 30.0mmol) and 12.6mg DBTDL. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0093] S3. Add chain extender HO-FDAM-OH (2.42g, 10.0mmol) and 0.2g silane coupling agent KH560 to the prepolymer and stir to polymerize for 1h.

[0094] S4. After cooling the reaction temperature to 50℃, add 30 mL of LDMF and chain extender FDHA (1.84 g, 10.0 mmol). Continue polymerization for 6 hours, then stop the reaction. Dry and remove solvent to obtain a light yellow solid product, namely furan-based polyurethane adhesive. The molecular weight was measured to be 58450 g / mol, and the intrinsic viscosity was 0.91 dL / g.

[0095] Example 23:

[0096] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0097] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 19mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0098] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (5.55g, 25.0mmol) and 11.3mg DBTDL. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0099] S3. Add chain extender HO-FDAM-OH (1.82g, 7.5mmol) and 0.19g silane coupling agent KH560 to the prepolymer and stir to polymerize for 1h.

[0100] S4. After cooling the reaction temperature to 50℃, add 30 mL of LDMF and chain extender FDHA (1.38 g, 7.5 mmol). Continue polymerization for 6 hours, then stop the reaction. Dry and remove solvent to obtain a light yellow solid product, namely furan-based polyurethane adhesive. The molecular weight was measured to be 47500 g / mol, and the intrinsic viscosity was 0.87 dL / g.

[0101] Example 24:

[0102] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0103] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 14.4mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0104] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (3.33g, 15.0mmol) and 8.6mg DBTDL. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0105] S3. Add chain extender HO-FDAM-OH (0.61g, 2.5mmol) and silane coupling agent KH560 to the prepolymer and stir to polymerize for 1h.

[0106] S4. After cooling the reaction temperature to 50℃, add 30 mL of LDMF and chain extender FDHA (0.46 g, 2.5 mmol). Continue polymerization for 6 hours, then stop the reaction. Dry and remove solvent to obtain a light yellow solid product, namely furan-based polyurethane adhesive. The molecular weight was measured to be 33260 g / mol, and the intrinsic viscosity was 0.62 dL / g.

[0107] Example 25:

[0108] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0109] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 17mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0110] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (4.44g, 20.0mmol) and 10mg DBTDL. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0111] S3. Add chain extender HO-FDAM-OH (2.033g, 8.4mmol) and 0.17g silane coupling agent KH560 to the prepolymer and stir to polymerize for 1h.

[0112] S4. After cooling the reaction temperature to 50℃, add 30 mL of LDMF and chain extender FDHA (0.294 g, 1.6 mmol). Continue polymerization for 6 hours, then stop the reaction. Dry and remove solvent to obtain a light yellow solid product, namely furan-based polyurethane adhesive. The molecular weight was measured to be 43800 g / mol, and the intrinsic viscosity was 0.73 dL / g.

[0113] Example 26:

[0114] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0115] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 16.5mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0116] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (4.44g, 20.0mmol) and 9.9mg DBTDL. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0117] S3. Add chain extender HO-FDAM-OH (0.823g, 3.4mmol) and silane coupling agent KH560 to the prepolymer and stir to polymerize for 1h.

[0118] S4. After cooling the reaction temperature to 50℃, add 30 mL of LDMF and chain extender FDHA (1.233 g, 6.7 mmol). Continue polymerization for 6 hours, then stop the reaction. Dry and remove solvent to obtain a light yellow solid product, namely furan-based polyurethane adhesive. The molecular weight was measured to be 32600 g / mol, and the intrinsic viscosity was 0.71 dL / g.

[0119] Comparative Example 1:

[0120] The difference from Example 25 is that chain extender II (FDHA) is not added.

[0121] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0122] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 17mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0123] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (4.44g, 20.0mmol) and 10mg DBTDL. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0124] S3. Add chain extender HO-FDAM-OH (2.42 g, 10.0 mmol) and 0.17 g silane coupling agent KH560 to the prepolymer. Add 30 mL of LDM to the reaction system, continue polymerization for 6 hours, then stop the reaction. After drying and solvent removal, a light yellow solid product is obtained. The molecular weight is measured to be 39450 g / mol, and the intrinsic viscosity is 0.67 dL / g.

[0125] Comparative Example 2:

[0126] The difference from Example 25 is that chain extender 1 (HO-FDAM-OH) is not added.

[0127] A method for synthesizing a furan-based polyurethane adhesive is as follows:

[0128] S1. Add PTMG-1000 (10.0g, 10.0mmol) and 16.3mg antioxidant 330 to a 250mL dry three-necked flask and vacuum at 120℃ for 2h to remove moisture from the raw materials to obtain the reaction solution.

[0129] S2. Cool the reaction solution to 70°C and backfill with nitrogen gas. Under nitrogen atmosphere, add IPDI (4.44g, 20.0mmol), 9.8mg DBTDL and 5ml LDMF. Stir the reaction at 70°C for 2 hours to obtain the prepolymer.

[0130] S3. Cool the reaction temperature to 50℃, add chain extender FDHA (1.84g, 10.0mmol) and silane coupling agent KH560 to the system, add 30mL LDM, continue polymerization for 6 hours, then stop the reaction. After drying and solvent removal, a light yellow solid product is obtained. The molecular weight is measured to be 59000g / mol, and the intrinsic viscosity is 0.98dL / g.

[0131] The furan-based polyurethane adhesives prepared in the examples and comparative examples were subjected to molecular weight and intrinsic viscosity tests. The number-average molecular weight (Mn) was determined by gel permeation chromatography (GPC); the intrinsic viscosity (ηr) was tested according to GB / T 10247-2008 "Methods for Viscosity Measurement".

[0132] The infrared spectrum, nuclear magnetic resonance spectrum, product molecular weight, and intrinsic viscosity of the polyurethane adhesives obtained in Examples 2-21 are basically consistent with the data of the polyurethane adhesive in Example 1. The molecular weight, intrinsic viscosity, and structure of the polyurethane adhesives obtained in Examples 2-21 all conform to the characteristics of polyurethane.

[0133] The furan-based polyurethane adhesives prepared in Examples 1, 22-26, and Comparative Examples 1-2 were used to prepare polyurethane films. The resulting polyurethane films were then subjected to tensile property tests and single-lap shear strength tests. The specific test methods are as follows:

[0134] (1) Tensile test: A 1 mm thick polyurethane film was placed in a 120°C hot press and hot-pressed at 15 MPa for 3 minutes. The resulting sample was then cut into dumbbell-shaped specimens with a length of 35 mm, a width of 2 mm, and a thickness of 1 mm. Tensile strength and elongation at break were tested using a commercial tensile testing machine (Suns Technology) equipped with a 1000 N sensor at a strain rate of 50 mm / min. Each measurement was repeated at least three times. Young's modulus was calculated from the initial slope of the linear phase of the stress-strain curve.

[0135] (2) Single lap shear strength test: A 0.2 mm thick polyurethane film was pressed on a 120°C hot press. The sample was cut into rectangles (25 mm × 12.5 mm) and placed between two substrates (100 mm × 25 mm × 1.5 mm) to form a 25 mm × 12.5 mm overlap. After securing the substrates with two paperclips, the sample was placed in a constant temperature oven and baked for 10 minutes. The sample was allowed to stand at room temperature for 24 hours before the test. The lap shear strength test was conducted using a universal tensile tester (Suns Technology) equipped with a 5000 N sensor, with a strain rate of 5 mm / min. Each test was repeated at least three times.

[0136] Examples 2-21 varied the vacuuming temperature, vacuuming time, reaction temperature, reaction time, and the amount or type of catalyst, antioxidant, silane coupling agent, and solvent. The resulting furan-based polyurethane adhesives had essentially the same properties as the furan-based polyurethane adhesives obtained in Example 1. The test results of Examples 2-21 will not be shown below.

[0137] Table 1: Molecular weight and intrinsic viscosity of furan-based polyurethane adhesives

[0138]

[0139] Table 1 shows the molecular weight and intrinsic viscosity of furan-based polyurethane adhesives. As shown in Table 1, the molecular weight (Mn) of the furan-based polyurethane adhesives synthesized in Examples 1, 22-26, and Comparative Examples 1-2 is relatively large, ranging from 32,600 to 59,000 g / mol, and the intrinsic viscosity (ηr) is between 0.62 and 0.98 dL / g.

[0140] Table 2: Performance Test Table for Furan-based Polyurethane Adhesives

[0141]

[0142] As shown in Table 2, the furan-based polyurethane adhesive synthesized in the examples exhibits high adhesion strength and mechanical properties, mainly due to the highly rigid structure of the two introduced chain extenders. These extenders react with isocyanate groups to form hard segments of the polyurethane. By adjusting the ratio of the two chain extenders to the polymer diol, the flexibility, rigidity, and adhesion of the material can be balanced, thus synthesizing a polyurethane adhesive with excellent overall performance. The furanyl amide and furanyl hydrazine chain extenders introduce amide and hydrazine groups into the polyurethane structure. The hydrazine groups can form a high-density hydrogen bond network, which is beneficial for improving the tensile strength and toughness of the material. Simultaneously, the resulting polyurethane film also exhibits high hydrolysis resistance. The amide groups and oxygen atoms on the furan ring can interact with hydroxyl groups or polar functional groups on the matrix, which is beneficial for improving the adhesion performance of the polyurethane material.

[0143] The difference between Comparative Example 1 and Example 25 is that furan-based polyurethane materials were synthesized without the addition of chain extender 2 (FDHA). Because FDHA was not introduced, its highly reactive hydrazide groups could not react with isocyanates to form strongly polar urea bonds, preventing the material from forming a physical cross-linked network composed of high-density, high-strength hydrogen bonds. This lack of a crucial network directly led to a significant deterioration in the material's tensile strength and cohesive energy.

[0144] The difference between Comparative Example 2 and Example 25 is that the furan-based polyurethane material was synthesized without the addition of chain extender 1 (HO-FDAM-OH). Due to the absence of amide groups in the molecule, the effective sites for strong interactions between the material and the substrate surface are significantly reduced, directly impairing the interfacial bonding performance of the adhesive and resulting in lower shear resistance. Therefore, the obtained product exhibits insufficient adhesion strength.

[0145] In summary, the furan-based polyurethane adhesive synthesized in this invention has high adhesion strength and mechanical strength, and the synthesis method is simple and easy to operate, making it applicable to fields such as construction, automobile manufacturing, medical, packaging, aerospace, and electronics.

[0146] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for synthesizing a furan-based polyurethane adhesive, characterized in that, The synthesis method of the furan-based polyurethane adhesive includes the following steps: S1. Add the polymer polyol and antioxidant to a dry three-necked flask, and evacuate at 120-140°C for 2-3 hours to obtain the reaction solution; S2. Cool the reaction solution to 70-90℃ and backfill with nitrogen gas. Under nitrogen atmosphere, add isocyanate and catalyst, stir and react for 2-3 hours to obtain prepolymer. S3. Add chain extender 1 and silane coupling agent to the prepolymer and stir to polymerize for 1-2 hours; S4. After cooling the reaction temperature to 40-50℃, add chain extender II, add solvent to the reaction system, adjust the viscosity of the reaction system, continue polymerization for 6-12 hours, stop the reaction, dry and remove solvent to obtain furan-based polyurethane adhesive. The polymer polyol is polytetrahydrofurandiol; the first chain extender is N,N-bis(2-hydroxyethyl)-2,5-furandicarboxamide; the second chain extender is 2,5-furandicarboxyhydrazide; and the isocyanate is isophorone diisocyanate.

2. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The structural formula of the furan-based polyurethane is:

3. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The molar ratio of chain extender one to chain extender two is 1:0.2 to 2.

4. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The ratio of the amount of the polymer polyol to the sum of the amounts of chain extender one and chain extender two is 1:0.5 to 2.

5. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The ratio of the amount of isocyanate to the sum of the amounts of polymer polyol, chain extender one, and chain extender two is 1:

1.

6. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The antioxidant is a hindered phenolic antioxidant, including at least one of antioxidant 1010, antioxidant 1076, antioxidant 1135, antioxidant 264, and antioxidant 330; the mass of the antioxidant is 0.1 to 0.3% of the total mass of the polymer polyol, chain extender one, chain extender two, and isocyanate.

7. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The silane coupling agent is at least one selected from γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane; the mass of the silane coupling agent is 0.5-2% of the total mass of the polymer polyol, chain extender one, chain extender two, and isocyanate.

8. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The catalyst is at least one of dibutyltin dilaurate, stannous oxalate, stannous octanoate, dibutyltin maleate, dibutyltin oxide, and monobutyltin oxide; the mass of the catalyst is 0.01 to 0.1% of the total mass of the polymer polyol, chain extender one, chain extender two, and isocyanate.

9. The method for synthesizing a furan-based polyurethane adhesive according to claim 1, characterized in that, The solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; the solvent is added to adjust the viscosity of the reaction system to 10-30 Pa·s.

10. A furan-based polyurethane adhesive, characterized in that, It is obtained by the synthesis method according to any one of claims 1 to 9.

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