Transparent strong-adhesion self-repairing recyclable adhesive and preparation method thereof

Abstract

The invention discloses a transparent strong-adhesion self-repairing recoverable adhesive and a preparation method thereof. The preparation method comprises the following steps: selecting hydroxyl functionalized cage type polysilsesquioxane, and preparing a plurality of cage type compounds with different terminal hydroxyl groups by utilizing diisocyanate, diethanol amine or trihydroxymethyl methylamine through a monomer coupling method; the polyurethane adhesive is prepared from polytetrahydrofuran, a diisocyanate monomer, thioformyl dihydrazine, a polyhedral oligomeric compound and an initiator through a polymerization addition reaction. And dispensing the transparent adhesive on the surface of the sample, and heating and curing to prepare the self-repairing recoverable polymer protective functional material. The adhesive prepared by the invention has strong interface adhesion strength and broad-spectrum material applicability, can realize self-recovery of the surface and the recovery characteristic of maintaining the strength through a thermal / solvent dual repair strategy, resists high and low temperatures and artificial seawater media, is expected to be applied to long-acting repairable application of ocean engineering bridge equipment, and has wide application prospects. And the engineering maintenance periodicity is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the field of functional adhesive preparation / construction, and in particular relates to a method for preparing a transparent, strong-adhesion, self-repairing, and recyclable adhesive. Background Art

[0002] The surfaces of heavy-duty marine equipment are subject to uncontrollable localized damage in marine environments, often caused by the coupling of multiple factors, including seawater, marine climate, salt spray, and ultraviolet light. This poses a significant challenge to the underwater interface protection of marine engineering equipment, such as submarines, bridges, and drilling platforms. Irreversible damage to protective materials can expose metal / concrete surfaces on some equipment, exposing them to degradation in service performance. Developing surface protection technologies that can maintain strength, self-repair, and provide long-term engineering serviceability (strong interface adhesion and resistance to environmental media) to mechanical damage on the surfaces of heavy-duty marine equipment holds significant scientific significance and potential application value.

[0003] Traditional marine protective materials usually use polyurea materials. Polyurea has attracted widespread attention for its resistance to marine environmental corrosion, impact resistance, and waterproof properties. For example, Chinese invention patent CN115895558A proposes a polyurea adhesive prepared by Michael addition reaction of a primary amino compound and an itaconate to form a secondary amine compound. Although the new adhesive has excellent interfacial adhesion strength, there is no self-repairing property / recyclability that can maintain the strength. Chinese invention patent CN105778844A proposes a polyurea adhesive formed by a diisocyanate and an amino-terminated diamine-type polyamide prepolymer, which has relatively low interfacial adhesion strength and water resistance and solvent resistance, and can be reused many times. Chinese invention patent CN119264793A proposes an aspartic acid ester-type polyurea adhesive with moisture insensitivity, strong adhesion, corrosion resistance, anti-yellowing and other properties. The above patents still face the problems of high interfacial adhesion strength that is difficult to meet actual working conditions, and the mismatch of mechanical properties under self-repairing / multiple use conditions. Therefore, it is necessary to develop a new synthesis technology for self-healing and recyclable adhesives, which can have the characteristics of multiple self-healing and intrinsic strong interfacial adhesion with maintained strength. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a transparent strong-adhesion self-repairing recyclable adhesive and a preparation method thereof which are simple, low-cost and have high transparency.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A method for preparing a transparent, strong-adhesion, self-repairing, recyclable adhesive comprises the following steps:

[0007] S1, dissolving a hydroxyl-functionalized cage-type polysilsesquioxane and hexamethylene diisocyanate in an organic solvent, then adding an excess of hexamethylene diisocyanate dropwise under nitrogen protection, and heating the mixture to cause a polyaddition reaction to obtain an organic-inorganic hybrid polyurethane prepolymer solution;

[0008] S2, adding diethanolamine or trimethylolmethylamine to the organic-inorganic hybrid polyurethane prepolymer solution to react, and then performing rotary evaporation on the obtained product solution to remove the high-boiling point solvent to obtain a light yellow oily substance, which is a multi-branched cage compound;

[0009] S3, dissolving polytetrahydrofuran and a catalyst dibutyltin dilaurate in an organic solvent, then adding an excess of diisocyanate monomer dropwise under a nitrogen atmosphere, and heating the mixture to cause a polyaddition reaction to obtain a polyurethane prepolymer solution;

[0010] S4, adding the multi-branched cage compound and thioformyl dihydrazide to the polyurethane prepolymer solution obtained in step S3 for reaction, then subjecting the obtained product solution to rotary evaporation to remove the high boiling point solvent, and adding a mixed solvent of tetrahydrofuran and ethyl acetate to prepare a coating;

[0011] S5. Apply the coating obtained in step S4 to the surface of the sample and solidify it to obtain a transparent, strong-adhesion, self-repairing, and recyclable adhesive.

[0012] Preferably, in the above-mentioned method for preparing the transparent strong-adhesion self-repairing recyclable adhesive, the molar ratio of the hydroxyl-functionalized cage-type polysilsesquioxane and hexamethylene diisocyanate in step S1 is 1:8-8.5, the heating temperature is 45-65°C, and the reaction time is 4-8 hours.

[0013] Preferably, in the above-mentioned method for preparing the transparent strong-adhesion self-repairing recyclable adhesive, the molar ratio of the organic-inorganic hybrid polyurethane prepolymer and diethanolamine or trimethylolmethylamine described in step S2 is 1:1-1.2, the reaction temperature is room temperature, and the reaction time is 4-8 hours.

[0014] Preferably, in the above-mentioned method for preparing a transparent, strongly adhesive, self-repairable, recyclable adhesive, the molar ratio of polytetrahydrofuran and diisocyanate in step S3 is 1:2-3, the mass fraction of the catalyst dibutyltin dilaurate is 0.5-1.5%, the reaction temperature is 60-80°C, and the reaction time is 2-8 hours; the diisocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, dimer acid diisocyanate and hexamethylene diisocyanate.

[0015] Preferably, in the above-mentioned method for preparing the transparent strong-adhesion self-repairing recyclable adhesive, the total molar fraction of the multi-branched cage compound and thioformyl dihydrazide described in step S4 is 100%, the molar ratio is 5-20:95-80, the reaction temperature is 40-60°C, and the reaction time is 4-24 hours.

[0016] Preferably, in the above-mentioned method for preparing the transparent strong-adhesion self-repairable recyclable adhesive, the curing in step S5 is heat curing.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The sample after drop coating of the present invention has excellent transparency (81.3%) on the surface of engineering materials, good adhesion, and the bonding strength on the surface of inorganic bare glass reaches 14.22MPa, and the bonding strength on the surface of metal 316L substrate reaches 26.43MPa, and has a wide spectrum of substrate applicability (plastic, inorganic, metal); (2) The sample after drop coating of the present invention can achieve self-recovery of surface damage through a dual self-repair strategy of heat / solvent assisted self-repair, and can be chemically recycled through multiple high-polarity solvents. The mechanical properties after multiple recycling can still maintain 73% of the original; (3) The adhesive constructed by the present invention has excellent weather resistance, UV resistance, high and low temperature resistance, acid, alkali and salt medium resistance, and has an interfacial adhesion of at least 7.32MPa after 168h of service verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are various test diagrams for adhesives, among which Figure a is the interface adhesion diagram, Figure b is the digital diagram of the pull-out failure interface, Figure c is the adhesive optical transparency test, and Figure d is the adhesive lap adhesion load-bearing diagram.

[0020] Figure 2 These are optical microscope images of the self-repair of heat-treated scratched surfaces; Figure a is a comparison of the disappearance of original scratches and crack areas on the adhesive surface after the adhesive surface was heat-treated at 110°C for 36 hours; Figure b is a comparison of the recovery of damaged surface areas after self-repair assisted by N,N-dimethylacetamide at 50°C for 30 minutes; Figure C is a schematic diagram of multiple uses of chemical recycling of adhesives; and Figure d is a diagram of the interface adhesion strength after multiple uses of chemical recycling.

[0021] Figure 3 These are the bridge pier immersion test diagrams, where Figure a is a schematic diagram of simulating the immersion of bridge pier components in marine engineering, Figure b is the engineering durability test under ultraviolet and high / low temperature conditions, and Figure c is the engineering durability test under acidic, alkaline and salt water conditions. DETAILED DESCRIPTION

[0022] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0023] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0024] Example 1: Preparation of a transparent, strong-adhesion, self-repairing, recyclable adhesive

[0025] (1) 1 g of hydroxyl-functionalized cage-type polysilsesquioxane (0.58 mmol) was dissolved in 10 ml of N,N-dimethylacetamide. 0.78 g of hexamethylene diisocyanate (4.64 mmol) was added under a nitrogen atmosphere. The reaction mixture was maintained at 45°C for 8 hours.

[0026] (2) Add 0.49 g of diethanolamine (4.64 mmol) or 0.56 g of tris(hydroxymethyl)aminomethane (4.64 mmol) at room temperature and continue the reaction for 4 hours. After the reaction is completed, the organic solvent is removed under reduced pressure, and the resulting product is washed three times with diethyl ether to obtain a light yellow viscous substance, which is a multibranched cage compound.

[0027] (3) 1.30 g of polytetramethyl ether glycol (2.00 mmol) was heated at 120°C for 1 hour to remove residual moisture. After cooling to 80°C, 1.05 g of dicyclohexylmethane diisocyanate (4.00 mmol) dissolved in 30 ml of N,N-dimethylacetamide was added dropwise through a constant pressure dropping funnel and reacted for 3 hours to prepare a prepolymer.

[0028] (4) Subsequently, 95 mol% of thioformyl dihydrazide and 5 mol% of a multibranched cage compound were dissolved in 20 ml of N,N-dimethylacetamide and added to the prepolymer. After reacting at 40°C for 24 hours, the high-boiling point solvent was removed, and a mixed solvent of tetrahydrofuran and ethyl acetate was added to prepare a coating.

[0029] (5) The mixed coating obtained in step (4) is dripped onto a glass substrate and heated to cure to obtain a transparent, strong-adhesion, self-repairing, recyclable adhesive. According to the national standard "GB / T 5210-2006 Adhesion test of paint and varnish by pull-off method", the cured rust-coated anti-corrosion coating is subjected to a coating-substrate bonding strength test. The aluminum ingot is adhered to the surface of the coating sample with HY-914 fast adhesive. After the adhesive is cured for 24 hours, the coating is cut along the edge of the aluminum ingot with a tool. The aluminum ingot is pulled off with an adhesion tester model F506-20D, and the results are as follows. Figure 1 As shown in a, the adhesion force is 26.43 MPa, indicating that the prepared transparent physical and chemical adhesive has excellent adhesion; Figure 1 As shown in b, the damage between the adhesive and the substrate is mainly interfacial damage; the adhesive was prepared on the bare glass surface and the transmittance at 550nm wavelength was quantitatively characterized by UV-Vis test, which was about 83.37% ( Figure 1 c). The adhesive is bonded to two bare glass substrates to form a lap joint structure that can withstand the weight of a 55kg adult ( Figure 1 d), the test proves that the adhesive has strong interfacial adhesion properties.

[0030] Example 2: Preparation of a transparent, strong-adhesion, self-repairing, recyclable adhesive

[0031] (1) 1 g of hydroxyl-functionalized cage-type polysilsesquioxane (0.58 mmol) was dissolved in 10 ml of N,N-dimethylacetamide. 0.78 g of hexamethylene diisocyanate (4.64 mmol) was added under a nitrogen atmosphere. The reaction mixture was maintained at 55°C for 6 hours.

[0032] (2) Add 0.49 g of diethanolamine (4.64 mmol) or 0.56 g of tris(hydroxymethyl)aminomethane (4.64 mmol) at room temperature and continue the reaction for 6 hours. After the reaction is completed, the organic solvent is removed under reduced pressure, and the resulting product is washed three times with diethyl ether to obtain a light yellow viscous substance, which is a multibranched cage compound.

[0033] (3) 1.30 g of polytetramethyl ether glycol (2.00 mmol) was heated at 120°C for 1 hour to remove residual moisture. After cooling to 70°C, 1.11 g of isophorone diisocyanate (5.00 mmol) dissolved in 30 ml of N,N-dimethylacetamide was added dropwise through a constant pressure dropping funnel and reacted for 4 hours to prepare a prepolymer.

[0034] (4) Subsequently, 90 mol% of thioformyl dihydrazide and 10 mol% of a multibranched cage compound were dissolved in 20 ml of N,N-dimethylacetamide and added to the prepolymer. After reacting at 50°C for 12 hours, the high-boiling point solvent was removed, and a mixed solvent of tetrahydrofuran and ethyl acetate was added to prepare a coating.

[0035] (5) The mixed coating obtained in step (4) is dripped onto a glass substrate and heated to cure to obtain a transparent, strong-adhesion, self-repairing, recyclable adhesive. After the adhesive surface is heat-treated at 110°C for 36 hours, the original scratches / cracks on the adhesive surface disappear ( Figure 2 a); After 30 minutes of self-repair assisted by N, N-dimethylacetamide at 50℃, the damaged area on the surface recovered ( Figure 2 b); Figure 2 As shown in Figure c, the multiple utilization of polymer materials is achieved through the high-polarity solvent chemical recovery of adhesive fragments-high temperature annealing process. The adhesive interface adhesion strength of the metal copper substrate surface after multiple uses is only reduced by 26.4%, and the bare glass substrate surface is reduced by 26.7% ( Figure 2 d), indicating that the adhesive not only has strong adhesion but also has reliable self-healing and recyclable properties.

[0036] Example 3: Preparation of a transparent, strong-adhesion, self-repairing, recyclable adhesive

[0037] (1) Dissolve 1 g of hydroxyl-functionalized cage-type polysilsesquioxane (0.58 mmol) in 10 ml of N,N-dimethylacetamide. Add 0.78 g of hexamethylene diisocyanate (4.64 mmol) under a nitrogen atmosphere. Maintain the reaction mixture at 65°C for 4 hours.

[0038] (2) Add 0.49 g of diethanolamine (4.64 mmol) or 0.56 g of tris(hydroxymethyl)aminomethane (4.64 mmol) at room temperature and continue the reaction for 8 hours. After the reaction is completed, remove the organic solvent under reduced pressure, and wash the resulting product three times with diethyl ether to obtain a light yellow viscous substance, which is a multibranched cage compound.

[0039] (3) 1.30 g of polytetramethyl ether glycol (2.00 mmol) was heated at 120°C for 1 hour to remove residual moisture. After cooling to 60°C, 1.13 g of diphenylmethane diisocyanate (4.50 mmol) dissolved in 30 ml of N,N-dimethylacetamide was added dropwise through a constant pressure drop funnel and reacted for 8 hours to prepare a prepolymer.

[0040] (4) Subsequently, 80 mol% of thioformyl dihydrazide and 20 mol% of a multibranched cage compound were dissolved in 20 ml of N,N-dimethylacetamide and added to the prepolymer. After reacting at 60°C for 4 hours, the high-boiling point solvent was removed, and a mixed solvent of tetrahydrofuran and ethyl acetate was added to prepare a coating.

[0041] (5) The mixed coating obtained in step (4) is dripped onto a glass substrate and heated to cure to obtain a transparent, strong-adhesion, self-repairing, recyclable adhesive. Figure 3 As shown in Figure a, the adhesive was applied to the surface of the bridge pier (45# steel) and subjected to simulated artificial seawater immersion tests to simulate the weather resistance of the coating under UV, high and low temperature, acid, alkali and salt media environments. After 168 hours of UV, high and low temperature tests, the adhesion strength was 9.73MPa, 20.68MPa and 12.34MPa, respectively, which decreased by 56.7%, 7.9% and 45.0% ( Figure 3 b). Figure 3 As shown in Figure c, after 168 hours of acid, alkali and salt medium immersion tests, the adhesion forces were 9.38 MPa, 7.32 MPa and 18.89 MPa, respectively, which decreased by 58.2%, 67.4% and 15.9%, respectively, indicating that the adhesive has significant resistance to high and low temperatures and salt water media.

[0042] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a transparent, strong-adhesion, self-repairing, recyclable adhesive, characterized in that: The following steps are involved: S1, dissolving a hydroxyl-functionalized cage-type polysilsesquioxane and hexamethylene diisocyanate in an organic solvent, then adding an excess of hexamethylene diisocyanate dropwise under nitrogen protection, and heating the mixture to cause a polyaddition reaction to obtain an organic-inorganic hybrid polyurethane prepolymer solution; S2, adding diethanolamine or trimethylolmethylamine to the organic-inorganic hybrid polyurethane prepolymer solution to carry out a reaction, and then performing rotary evaporation on the obtained product solution to remove the high-boiling point solvent to obtain a light yellow oily substance, which is a multi-branched cage compound; S3, dissolving polytetrahydrofuran and a catalyst dibutyltin dilaurate in an organic solvent, then adding an excess of diisocyanate monomer dropwise under nitrogen protection, and heating to cause a polyaddition reaction to obtain a polyurethane prepolymer solution; S4, adding the multi-branched cage compound and thioformyl dihydrazide to the polyurethane prepolymer solution obtained in step S3 for reaction, then subjecting the obtained product solution to rotary evaporation to remove the high boiling point solvent, and adding a mixed solvent of tetrahydrofuran and ethyl acetate to prepare a coating; S5. Apply the coating obtained in step S4 to the surface of the sample and solidify it to obtain a transparent, strong-adhesion, self-repairing, and recyclable adhesive.

2. The method for preparing the transparent strong-adhesion self-repairing recyclable adhesive according to claim 1, characterized in that: The molar ratio of the hydroxyl-functionalized cage-type polysilsesquioxane to hexamethylene diisocyanate in step S1 is 1:8-8.5, the heating temperature is 45-65° C., and the reaction time is 4-8 hours.

3. The method for preparing the transparent strong-adhesion self-repairing recyclable adhesive according to claim 1, characterized in that: The molar ratio of the organic-inorganic hybrid polyurethane prepolymer and diethanolamine or trimethylolmethylamine in step S2 is 1:1-1.2, the reaction temperature is room temperature, and the reaction time is 4-8 hours.

4. The method for preparing the transparent strong-adhesion self-repairing recyclable adhesive according to claim 1, characterized in that: The molar ratio of polytetrahydrofuran to diisocyanate in step S3 is 1:2-3, the mass fraction of the catalyst dibutyltin dilaurate is 0.5-1.5%, the reaction temperature is 60-80°C, and the reaction time is 2-8 hours; the diisocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, dimer acid diisocyanate and hexamethylene diisocyanate.

5. The method for preparing the transparent strong-adhesion self-repairing recyclable adhesive according to claim 1, characterized in that: The total molar fraction of the multi-branched cage compound and thiocarboxamide dihydrazide in step S4 is 100%, the molar ratio is 5-20:95-80, the reaction temperature is 40-60° C., and the reaction time is 4-24 hours.

6. The method for preparing the transparent strong-adhesion self-repairing recyclable adhesive according to claim 1, characterized in that: The curing in step S5 is heat curing.

7. A transparent strong adhesion self-repairing recyclable adhesive, characterized in that Prepared by the method according to any one of claims 1 to 6.

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