A recyclable adhesive suitable for bonding different substrates, and a preparation method and application thereof

Abstract

The application discloses a recyclable adhesive suitable for bonding different substrates and a preparation method and application thereof, and relates to the technical field of adhesives. The recyclable adhesive comprises the following components in parts by weight: 20-40 parts of a polyamine monomer, 3-8 parts of a diisothiocyanate monomer and 3-8 parts of modified tannic acid. The preparation method comprises the following steps: preparing modified tannic acid; mixing the diisothiocyanate and the polyamine monomer to generate an isothiocyanate group-terminated prepolymer; and mixing the modified tannic acid and the isothiocyanate group-terminated prepolymer, covalently cross-linking through a Michael addition reaction to obtain the recyclable adhesive.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, more particularly to a recyclable adhesive suitable for bonding different substrates and a preparation method and application thereof. BACKGROUND

[0002] Wood adhesives play an increasingly important role in wood processing, furniture manufacturing and construction. The main wood adhesives on the market include urea-formaldehyde (UF), phenol-formaldehyde (PF) and melamine-formaldehyde (MF) adhesives. These adhesives have good performance, but have some problems, such as non-renewable raw materials, release of harmful substances such as formaldehyde, etc. Therefore, people have begun to turn to the development of biomass-based adhesives.

[0003] Biomass-based adhesives use renewable biomass resources such as cellulose, tannin, lignin, soy protein and tannic acid. Among them, tannic acid is considered as a substitute for traditional formaldehyde-based adhesives due to its biocompatibility, biodegradability and film-forming ability. However, the high brittleness and low water resistance of tannic acid limit its application. To solve these problems, researchers have adopted various methods, such as adding plasticizers, crosslinking modification and building branched structures. The use of dendrimers as crosslinking agents can improve the bonding performance and water resistance of tannic acid-based adhesives, but may increase brittleness. Hyperbranched adhesives, especially polyamides, can effectively enhance the toughness of thermosetting resins due to their unique structure and properties. Diisothiocyanate monomers improve the bonding strength due to the introduction of rigid aromatic ring structures.

[0004] At present, there is a lack of a safe and environmentally friendly biomass recyclable adhesive and a preparation method thereof SUMMARY

[0005] The present application aims to overcome the defects or deficiencies in the prior art that the temperature for bonding substrates is high and a large amount of formaldehyde is released, and to provide a recyclable biomass adhesive. The adhesive provided by the present application contains characteristic dynamic reversible thiourea bond units, which endow the adhesive with solvent solubility and recyclability, thereby enhancing the use stability of the material and prolonging the service life.

[0006] Another object of the present application is to provide a preparation method of the recyclable biomass adhesive described above.

[0007] Another object of the present application is to provide a preparation method of the modified tannin recyclable adhesive described above.

[0008] Another object of the present application is to provide the application of the adhesive described above in recyclable biomass adhesives.

[0009] In order to achieve the above-mentioned objects, the present application adopts the following technical solutions:

[0010] A recyclable adhesive suitable for bonding different substrates, comprising the following components by weight:

[0011] 20-40 parts of polyamine monomer, 3-8 parts of diisothiocyanate monomer, and 3-8 parts of modified tannic acid.

[0012] Preferably, the modified tannic acid is prepared by the following method:

[0013] Take 1-10 parts of tannic acid, add 1.2-15 parts of 4-dimethylaminopyridine and 3.6-50 parts of acrylic anhydride, put them into a flask, place the flask in an ultrasonic water bath with a power of 60-80W, and stir at 300-500r / min at 60-90℃ for 12-24h; after the reaction is completed, cool the flask to room temperature, wash the mixture successively with ethyl acetate, 0.5mol / L NaOH, saturated NaHCO3 solution and water, and dry under vacuum to obtain the modified tannic acid.

[0014] Preferably, the polyamine monomers include: polyamide 651 and polyamide 650.

[0015] The method for preparing the above-mentioned recyclable adhesive for bonding different substrates includes the following steps:

[0016] (1) Preparation of modified tannic acid;

[0017] (2) Diisothiocyanate and polyamine monomers are mixed to generate isothiocyanate-terminated prepolymers;

[0018] (3) Mix 3-8 parts of modified tannic acid and 3-8 parts of isothiocyanate-based end-capped prepolymer and covalently crosslink them through Michael addition reaction to obtain a recyclable adhesive.

[0019] Preferably, step (2) specifically includes: taking 20-40 parts of polyamine monomer, placing it in a flask, adding 5-20 parts of N,N dimethylformamide, stirring at room temperature until fully dissolved to obtain a polyamine monomer solution, taking 3-8 parts of diisothiocyanate and dissolving it in 5-20 parts of N,N dimethylformamide to obtain a diisothiocyanate solution, slowly adding the diisothiocyanate solution to the polyamine monomer solution using a constant pressure funnel and stirring at 60-100°C for 6-12 hours to obtain the isothiocyanate-terminated prepolymer.

[0020] Preferably, the covalent crosslinking package in step (3) is:

[0021] Modified tannic acid and isothiocyanate-terminated prepolymer were mixed, and then 1,8-diazabicyclo[5.4.0]undec-7-ene was added to carry out a Michael addition reaction.

[0022] Among them, the C=C double bond of the modified tannic acid and the -NH4 of the thiocyanate-terminated prepolymer undergo a Michael addition reaction.

[0023] The above-mentioned recyclable adhesives suitable for bonding different substrates are applied to the surfaces of different substrates;

[0024] The substrate includes: wood, bamboo, metal, polytetrafluoroethylene, polyvinyl chloride, plexiglass or inorganic glass;

[0025] The timber includes: beech and poplar;

[0026] The metal includes steel, aluminum, or copper.

[0027] The recyclable adhesive is applied to the surface of the substrate and hot-pressed at 60°C-100°C for 600-6000 seconds, and then left at room temperature for 12-24 hours to eliminate internal stress.

[0028] After use, scrape off the recyclable adhesive that is bonded to the substrate, dissolve it in N,N dimethylformamide, and regenerate the adhesive at 60-100°C to continue bonding the substrate.

[0029] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0030] Compared to most adhesives on the market, it can bond at relatively lower temperatures, reducing energy consumption. At the same time, it can be recycled, increasing the practicality of the adhesive. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the mechanism of the modified tannins of this invention.

[0033] Figure 2 This is a strength diagram showing the overlapping of different substrates according to the present invention.

[0034] Figure 3 This is a stress-strain diagram of different substrates being joined together in the steps of this invention.

[0035] Figure 4 Infrared spectra of the modified tannic acid™ and the raw materials used in this invention.

[0036] Figure 5Infrared spectrum of isothiocyanate-terminated prepolymer TD prepared according to the present invention. Detailed Implementation

[0037] 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.

[0038] This invention discloses a high-performance biomass-based recyclable adhesive, the preparation method of which includes:

[0039] (1) Preparation of modified tannic acid: Take 1-10 parts of tannic acid, add 1.2-15 parts of 4-dimethylaminopyridine and 3.6-50 parts of acrylic anhydride, put them into a flask, place the flask in an ultrasonic water bath with a power of 60-80W, and stir at 300-500r / min at 60-90℃ for 12-24h; after the reaction is completed, cool the flask to room temperature, wash the mixture with ethyl acetate, 0.5mol / L NaOH, saturated NaHCO3 solution and water in sequence, and dry under vacuum to obtain the modified tannic acid;

[0040] (2) Take 20-40 parts of polyamine monomer, put them into a flask, add 5-20 parts of N,N dimethylformamide and stir at room temperature until fully dissolved to obtain a polyamine monomer solution. Take 3-8 parts of diisothiocyanate and dissolve it in 5-20 parts of N,N dimethylformamide to obtain a diisothiocyanate solution. Slowly add the diisothiocyanate solution to the polyamine monomer solution using a constant pressure funnel and stir at 60-100℃ for 6-12 hours to obtain the isothiocyanate-terminated prepolymer.

[0041] (3) Mix 3-8 parts of modified tannic acid and 3-8 parts of isothiocyanate-based end-capped prepolymer, and then add DUB catalyst to covalently crosslink through Michael addition reaction to obtain recyclable adhesive.

[0042] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] All quantities mentioned in the following examples are by weight.

[0044] Example 1

[0045] This embodiment provides a high-performance biomass-based recyclable adhesive (hereinafter referred to as adhesive), the preparation process of which is as follows:

[0046] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0047] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0048] Example 2

[0049] This embodiment provides a high-performance biomass-based recyclable adhesive (hereinafter referred to as adhesive), the preparation process of which is as follows:

[0050] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 3 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0051] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0052] Example 3

[0053] This embodiment provides a high-performance biomass-based recyclable adhesive (hereinafter referred to as adhesive), the preparation process of which is as follows:

[0054] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 8 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0055] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0056] Example 4

[0057] This embodiment provides a high-performance biomass-based recyclable adhesive (hereinafter referred to as adhesive), the preparation process of which is as follows:

[0058] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0059] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 3 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0060] Example 5

[0061] This embodiment provides a high-performance biomass-based recyclable adhesive (hereinafter referred to as adhesive), the preparation process of which is as follows:

[0062] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0063] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 8 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0064] Example 6

[0065] This embodiment provides a high-performance biomass-based recyclable adhesive (hereinafter referred to as adhesive), the preparation process of which is as follows:

[0066] (1) Under a nitrogen atmosphere, take 20 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0067] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0068] Example 7

[0069] This embodiment provides a high-performance biomass-based recyclable adhesive (hereinafter referred to as adhesive), the preparation process of which is as follows:

[0070] (1) Under a nitrogen atmosphere, take 40 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0071] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0072] Example 8

[0073] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0074] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0075] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond wood and hot-press at room temperature for 24 h. The adhesive is dissolved and re-bonded to prepare new samples, which can recover some mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0076] Example 9

[0077] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0078] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0079] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 60℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0080] Example 10

[0081] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0082] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0083] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the wood and hot-press at 100℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0084] Example 11

[0085] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0086] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0087] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond bamboo and hot press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0088] Example 12

[0089] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0090] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0091] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond stainless steel and hot press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could recover some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0092] Example 13

[0093] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0094] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0095] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond it to an aluminum substrate and hot press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could recover some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0096] Example 14

[0097] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0098] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0099] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond the adhesive to a copper substrate and hot press at 80℃ for 90 min. The adhesive was dissolved and re-bonded to prepare new samples, which could restore some of the mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0100] Example 15

[0101] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0102] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0103] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond polyvinyl chloride and hot press at 80℃ for 90 min. The adhesive is dissolved and re-bonded to prepare new samples, which can recover some mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0104] Example 16

[0105] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0106] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0107] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond polytetrafluoroethylene and hot press at 80℃ for 90 min. The adhesive is dissolved and re-bonded to prepare new samples, which can recover some mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0108] Example 17

[0109] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0110] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0111] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond it to plexiglass and hot press at 80℃ for 90 min. The adhesive is dissolved and re-bonded to prepare new samples, which can recover some mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0112] Example 18

[0113] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0114] (1) Under a nitrogen atmosphere, take 30 parts of polyamide 651, put it into a flask, add 10 parts of NN dimethylformamide and stir at room temperature until fully dissolved, take 5 parts of diisothiocyanate and dissolve it in 10 parts of NN dimethylformamide, slowly add the dissolved diisothiocyanate dropwise through a constant pressure funnel and stir at 60°C for 6 hours to obtain isothiocyanate-terminated prepolymer;

[0115] (2) Take 5 parts of isothiocyanate-terminated prepolymer, then add 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid. React for 12 h, and remove excess DMF by rotary evaporation of the reaction product to obtain a viscous, high-performance biomass-based recyclable adhesive. Bond inorganic glass and hot press at 80℃ for 90 min. The adhesive is dissolved and re-bonded to prepare new samples, which can recover some mechanical strength. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0116] Comparative Example 1

[0117] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as adhesive), and its preparation process is as follows.

[0118] Under a nitrogen atmosphere, 30 parts of polyamide 650 were placed in a flask, and 10 parts of N,N-dimethylformamide were added and stirred at room temperature until fully dissolved. 5 parts of diisothiocyanate were dissolved in 10 parts of N,N-dimethylformamide. The dissolved diisothiocyanate was slowly added dropwise using a constant pressure funnel and stirred at 60°C for 6 hours. Then, 0.7 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene DUB catalyst and 5 parts of modified tannic acid were added, and the reaction continued for 12 hours. The reaction product was then rotary evaporated to remove excess DMF, yielding a viscous, high-performance biomass-based recyclable adhesive. This adhesive was used to bond wood and hot-pressed at 80°C for 90 minutes. New samples were prepared by dissolving and re-bonding the adhesive, and some mechanical strength was restored. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0119] Comparative Example 2

[0120] This embodiment provides a high-performance biomass-based adhesive (hereinafter referred to as the adhesive), the preparation process of which is as follows:

[0121] Under a nitrogen atmosphere, 30 parts of polyamide 651 were placed in a flask, and 10 parts of N,N-dimethylformamide were added and stirred at room temperature until fully dissolved. 5 parts of diisothiocyanate were dissolved in the 10 parts of N,N-dimethylformamide. The dissolved diisothiocyanate was slowly added dropwise through a constant-pressure funnel and stirred at 60°C for 6 hours. Then, 5 parts of modified tannic acid TM were added, and the reaction continued for 12 hours. The reaction product was rotary evaporated to remove excess DMF, yielding a viscous, high-performance biomass-based recyclable adhesive. This adhesive was used to bond wood and hot-pressed at 80°C for 90 minutes. New samples were prepared by dissolving and re-bonding the adhesive, and some mechanical strength was restored. The bonding strength results before and after adhesive recycling are shown in Table 1.

[0122] Table 1

[0123]

[0124]

[0125] As shown in the table, the prepared adhesive exhibits superior bonding performance to wood and bamboo. It penetrates the pores of the wood and bamboo to form a mechanical interlock. Furthermore, its adhesion to polytetrafluoroethylene (PTFE) is stronger than most commercially available adhesives. This is because the primary amine (-NH2) molecules of the polyamines possess "extra" hydrogen atoms. These hydrogen atoms can form coordinate bonds with the multi-electron structure of PTFE, thus achieving adhesion. In contrast, secondary and tertiary amines, lacking these extra hydrogen atoms, cannot form coordinate bonds with PTFE. The introduction of reversible dynamic bonds significantly improves the adhesive's recyclability, increases experimental applicability, and greatly reduces costs.

[0126] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0127] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a recyclable adhesive suitable for bonding different substrates, characterized in that, Includes the following steps: (1) Take 1-10 parts of tannic acid, add 1.2-15 parts of 4-dimethylaminopyridine and 3.6-50 parts of acrylic anhydride, put them into a flask, place the flask in an ultrasonic water bath with a power of 60-80W, and stir at 300-500 r / min at 60-90℃ for 12-24h; after the reaction is completed, cool the flask to room temperature, wash the mixture with ethyl acetate, 0.5mol / L NaOH, saturated NaHCO3 solution and water in sequence, and dry under vacuum to obtain modified tannic acid; (2) Take 20-40 parts of polyamine monomer, put them in a flask, add 5-20 parts of N,N-dimethylformamide, and stir at room temperature until fully dissolved to obtain a polyamine monomer solution. Take 3-8 parts of diisothiocyanate and dissolve it in 5-20 parts of N,N-dimethylformamide to obtain a diisothiocyanate solution. Slowly add the diisothiocyanate solution to the polyamine monomer solution using a constant pressure funnel and stir at 60-100℃ for 6-12 hours to obtain an isothiocyanate-terminated prepolymer. The polyamine monomer includes polyamide 651 or polyamide 650. (3) Mix 3-8 parts of modified tannic acid and 3-8 parts of isothiocyanate-based end-capped prepolymer and covalently crosslink them through Michael addition reaction to obtain a recyclable adhesive.

2. The method for preparing a recyclable adhesive suitable for bonding different substrates according to claim 1, characterized in that, The covalent crosslinking described in step (3) is as follows: Modified tannic acid and isothiocyanate-terminated prepolymer were mixed, and then 1,8-diazabicyclo[5.4.0]undec-7-ene was added to carry out a Michael addition reaction.

3. The application of the recyclable adhesive prepared by the method described in claim 1 or 2, suitable for bonding different substrates, in bonding different substrate surfaces.

4. The application according to claim 3, characterized in that, The substrate includes: wood, bamboo, metal, polytetrafluoroethylene, polyvinyl chloride, plexiglass or inorganic glass; The wood mentioned includes: beech and poplar; The metal includes steel, aluminum, or copper.

5. The application according to claim 4, characterized in that, The recyclable adhesive is applied to the surface of the substrate and hot-pressed at 60°C-100°C for 600-6000 seconds, and then left at room temperature for 12-24 hours to eliminate internal stress.

6. The application according to claim 5, characterized in that, After use, scrape off the recyclable adhesive that is bonded to the substrate, dissolve it in N,N-dimethylformamide, and regenerate the adhesive at 60-100°C to continue bonding the substrate.

Images