Targeted self-repairing polyurethane sealant and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane adhesives, and discloses a targeted self-repairing polyurethane sealant, which comprises a component A and a component B. The component A is a modified polyurethane prepolymer, and the raw materials comprise polyisocyanate, bio-based polyol, modified nano ferroferric oxide and an aprotic solvent; the component B is prepared from a modified chain extender, inorganic filler, a toughening agent, a bonding accelerant and a defoaming agent; the modified chain extender is prepared from the following raw materials: dialkyl dithiodiacetaldehyde, an aprotic solvent, dopamine and glacial acetic acid. And'on-demand 'and'accurate' triggering of the self-repairing process is realized. The stability, the viscosity, the difficulty in cracking and the aging resistance of the sealant at a high temperature are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane adhesives, in particular to a targeted self-repairing polyurethane sealant and a preparation method thereof. BACKGROUND

[0002] Polyurethane sealant is a high-performance, multi-purpose elastic sealing material, known for its excellent wear resistance, elasticity and strength. It has a wide range of applications in many fields such as construction, automobile, industry, etc. Self-repairing polyurethane material is a kind of polyurethane material that can restore its original structure and function autonomously, partially or completely without external intervention or external stimulus (such as heating, light) after being damaged (such as scratches, cracks, puncture).

[0003] Chinese patent document CN117736393A discloses a self-repairing bio-based polyurethane, mainly composed of polyisocyanate, bio-based polyol, dihydrazine compound, imidazole compound, solvent and deionized water, and the raw materials are proportioned as follows: 30-60 parts: 40-70 parts: 0.5-5 parts: 0.2-2 parts: 10-20 parts: 10-50 parts.

[0004] For example, Chinese patent document CN119060684B discloses a bio-based two-component polyurethane adhesive, which includes A component and B component with a mass ratio of 0.8-1.2:0.8-1.2, and the raw materials of A component include 3-5 parts of castor oil, 3-5 parts of epoxy soybean oil polyol, 10-15 parts of isocyanate, and 1-2 parts of carboxyl-terminated polyamide-amine; the raw materials of B component include 1-2 parts of tannic acid, 2-4 parts of lignin, 1-2 parts of dimethylglyoxime, 5-8 parts of castor oil alcohol, 3-5 parts of isocyanate, 1-2 parts of epoxy soybean oil, 1-2 parts of fly ash, and 1-2 parts of nano titanium dioxide.

[0005] In the prior art, polyurethane self-repairing is achieved through intrinsic self-repairing, i.e. relying on the chemical properties of the material. This method introduces dynamic reversible chemical bonds (such as Diels-Alder bond, disulfide bond, dynamic urethane bond, oxime bond, etc.) into the polyurethane molecular chain. When the material is damaged, these dynamic bonds break at the damage site and need to be reconnected by applying external stimulus (such as heating, light). The existing technology cannot achieve precise targeted self-repairing. SUMMARY

[0006] To solve the technical problem of how to achieve precise targeted self-repairing, the present application provides a targeted self-repairing polyurethane sealant, which includes A component and B component, characterized in that the A component is a modified polyurethane prepolymer, and the raw materials include polyisocyanate, bio-based polyol, nano-ferroferric oxide, and aprotic solvent; the B component includes a chain extender.

[0007] In order to promote the self-repairing effect, dopamine modified nano-Fe3O4 is used to avoid uniform dispersion of Fe3O4 and sedimentation, which is beneficial to realize precise and controllable local self-repairing in space.

[0008] In order to improve the bonding performance, the B component includes a modified chain extender, and the raw materials include dithiodialkyl bisacetaldehyde, an aprotic solvent, dopamine and glacial acetic acid, and multiple dynamic reversible covalent bonds such as dynamic oxime bond (C=N-O) and disulfide bond (S-S) are introduced to improve the self-repairing effect.

[0009] Preferably, the weight ratio of the A component and the B component is 100:10-20.

[0010] Preferably, the weight ratio of the raw materials in the A component is as follows: modified polyurethane prepolymer, raw materials including 150-200 parts of polyisocyanate, 80-100 parts of bio-based polyol, 1-3 parts of modified nano-Fe3O4 and 10-20 parts of aprotic solvent.

[0011] Preferably, the weight ratio of the raw materials in the modified chain extender of the B component is as follows: 20-30 parts of dithiodialkyl bisacetaldehyde, 100 parts of aprotic solvent, 40-50 parts of dopamine and 1-2 parts of glacial acetic acid.

[0012] Preferably, the B component further includes auxiliary additives: 15-20 parts of inorganic filler, 3-10 parts of toughening agent, 1-3 parts of adhesion promoter and 0.5-1 part of defoaming agent.

[0013] A preparation method of a targeted self-repairing polyurethane sealant, comprising the following steps:

[0014] Step 1, preparation of the A component: bio-based polyol is heated to remove water, polyisocyanate is added, continuous stirring is performed, then an aprotic solvent and dopamine modified nano-Fe3O4 particles are added and continuous stirring is performed to obtain a modified polyurethane prepolymer, which is the A component;

[0015] Step 2, preparation of the B component: dithiodialkyl bisacetaldehyde and an aprotic solvent are slowly added to dopamine and glacial acetic acid under nitrogen condition, the reaction system is heated and continuous stirring is performed to obtain a bio-based chain extender with dynamic oxime bond and disulfide bond, which is the B component;

[0016] Step 3, the A component and the B component are uniformly mixed at room temperature, then inorganic filler, toughening agent, adhesion promoter and defoaming agent are added to obtain the targeted self-repairing polyurethane sealant.

[0017] Preferably, the dopamine modified nano-Fe3O4 is prepared as follows: Fe 2+ / Fe 3+The nano Fe3O4 particles are generated by adding a base to a salt solution, pre-dried, dispersed in an aprotic solvent by ultrasonic, stirred under nitrogen protection, adding ammonia propyl triethoxysilane drop by drop into the dispersion, and heated to reflux to obtain amino-functionalized nano Fe3O4; then the system is heated, dopamine and glacial acetic acid are slowly added under nitrogen protection, and the stirring is continued to obtain dopamine-modified nano Fe3O4.

[0018] The present application has the following beneficial effects:

[0019] 1、Based on the unique interface design, the nanoparticles are prone to agglomerate into larger particles due to high surface energy, thereby losing the nanometer effect, and even becoming stress concentration points to cause the material performance to decrease. The catechol group of dopamine can be firmly anchored on the surface of the nano Fe3O4 to form an organic coating layer, effectively preventing agglomeration and ensuring uniform dispersion in the matrix, so that the nano Fe3O4 particles are stably and uniformly dispersed in the matrix, and the composite material has excellent magnetocaloric effect. The nano Fe3O4 is a magnetic material. When it is placed in a high-frequency alternating magnetic field, its magnetic moment will quickly flip with the high-speed change of the magnetic field direction, generating friction heat, thereby efficiently converting magnetic energy into heat energy. Under the action of an external alternating magnetic field, the dispersed magnetic particles can convert magnetic energy into heat energy, realizing precise and controllable local heating (targeted heating). The heat can further activate the dynamic oxime bond and disulfide bond in the matrix, significantly accelerating the breaking and recombination kinetics, thereby guiding and promoting the site-specific and preferential self-repair of the material at the damage site (targeted self-repair), and realizing the "on-demand" and "precise" triggering of the self-repair process. The nano Fe3O4 particles can strongly interact with the polyurethane molecular chain, effectively transfer and disperse stress, play a role in strengthening and toughening, improve the tensile strength, modulus and tear resistance of the sealant, and the uniformly distributed rigid nanoparticles can also act as physical crosslinking points to hinder the sliding of molecular chains and the expansion of microcracks, thereby improving the durability of the material and the stability, adhesion, resistance to cracking and aging resistance of the sealant at high temperatures.

[0020] 2、The nano Fe3O4 particles are synthesized by a chemical precipitation method, and the catechol group of dopamine is used to chemically graft and modify the surface of the nano Fe3O4 particles. This functional treatment not only solves the problem of easy agglomeration of nanoparticles in the polymer matrix, but more importantly, the terminal hydroxyl group (-OH) of the grafted dopamine molecules can act as an active reaction site and chemically react with the polyurethane prepolymer during the synthesis of polyurethane, thereby chemically bonding the nano Fe3O4 in situ, firmly and uniformly into the three-dimensional network of polyurethane.

[0021] 3. This invention uses bio-based dopamine as a raw material to improve the nano-ferric oxide in component A and the chain extender in component B. This not only improves the uniformity of nano-ferric oxide in the prepolymer and enhances the accuracy of self-repair, but also successfully constructs a single-component polyurethane sealant with both bio-based origin and high self-repair capability by introducing multiple dynamic reversible covalent bonds such as dynamic oxime bonds (C=NO) and disulfide bonds (SS) into its molecular structure. This dynamic network structure can undergo reversible breakage and recombination under specific external stimuli, thereby realizing the material's intrinsic self-repair. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method:

[0023] A targeted self-healing polyurethane sealant includes component A and component B. Component A is a modified polyurethane prepolymer, and its raw materials include polyisocyanate, bio-based polyol, modified nano-ferric oxide, and aprotic solvent. Component B includes a modified chain extender, inorganic filler, toughening agent, adhesion promoter, and defoamer. The modified chain extender raw materials include dithiodialkyl diacetaldehyde, aprotic solvent, dopamine, and glacial acetic acid.

[0024] The raw materials are as follows:

[0025] 1. Polyisocyanates: at least one of hexamethylene diisocyanate (HDI), bio-based 1,5-pentanediisocyanate (PDI), isoflurone diisocyanate (IPDI), etc.;

[0026] 2. Bio-based polyols: at least one of castor oil polyols, soybean oil polyols, palm oil polyols, etc.;

[0027] 3. Aprotic solvents: at least one of N,N-dimethylformamide, dimethyl sulfoxide, hexaoxide, etc.

[0028] 4. Adhesion promoter: at least one of oligomeric siloxanes, aminosiloxanes, vinyl oligomeric siloxanes, etc.;

[0029] 5. Inorganic filler: at least one of the following: gaseous silica, nano-calcium carbonate, kaolin, etc.

[0030] 6. Defoamer: Organosilicon defoamer;

[0031] 7. Toughening agent: at least one of dioctyl phthalate, tricresyl phosphate, dibutyl phthalate, etc.;

[0032] Example 1

[0033] A method for preparing a targeted self-healing polyurethane sealant includes the following steps:

[0034] Step 1, Preparation of Component A: Weigh 80 parts of bio-based polyol and heat it at 120℃ to remove water for 2 hours. Then lower the temperature to 80℃ and add 150 parts of polyisocyanate under nitrogen protection. Stir continuously for 1 hour. Then lower the temperature to 60℃ and add 10 parts of aprotic solvent and 1 part of nano-iron oxide particles. Stir continuously for 1 hour to obtain the modified polyurethane prepolymer, which is Component A.

[0035] Step 2, Preparation of Component B: Weigh 20 parts of dithiodialkyl diacetaldehyde and 100 parts of aprotic solvent into a three-necked flask. Under nitrogen conditions, slowly add 40 parts of dopamine and 1 part of glacial acetic acid. Heat the reaction system to 110°C and keep stirring for 10 hours to obtain a bio-based chain extender with dynamic oxime bonds and disulfide bonds, which is Component B.

[0036] Step 3: Mix component A and component B at a weight ratio of 100:10 at room temperature until homogeneous. Then add 15 parts inorganic filler, 3 parts toughening agent, 1 part adhesion promoter, and 0.5 parts defoamer to obtain the targeted self-healing polyurethane sealant.

[0037] Example 2

[0038] A method for preparing a targeted self-healing polyurethane sealant includes the following steps:

[0039] Step 1: Preparation of dopamine-modified nano-Fe3O4: Nano-Fe3O4 particles were prepared using a co-precipitation method. The co-precipitation method mainly involves the precipitation of Fe3O4 particles. 2+ / Fe 3+ An alkaline environment was provided by adding alkali to the salt solution, ultimately generating nano-Fe3O4 particles. 15 parts of nano-Fe3O4 particles were weighed and pre-dried in an oven at 120°C for 1 hour. They were then ultrasonically dispersed in 100 parts of an aprotic solvent. Under nitrogen protection and mechanical stirring, 4 parts of aminopropyltriethoxysilane were added dropwise to the dispersion, and the mixture was heated to 80°C and refluxed for 24 hours to obtain aminated nano-Fe3O4. The system was then heated to 110°C, and 10 parts of dopamine and 2 parts of glacial acetic acid were slowly added under nitrogen protection, with continuous stirring for 12 hours to obtain dopamine-modified nano-Fe3O4.

[0040] Step 2, Preparation of Component A: Weigh 80 parts of bio-based polyol and heat it at 120℃ to remove water for 2 hours. Then lower the temperature to 80℃ and add 150 parts of polyisocyanate under nitrogen protection. Stir continuously for 1 hour. Then lower the temperature to 60℃ and add 10 parts of aprotic solvent and 1 part of dopamine-modified nano-iron oxide particles. Stir continuously for 1 hour to obtain modified polyurethane prepolymer, which is Component A.

[0041] Step 3, Preparation of Component B: Weigh 20 parts of disulfide dialkyl diacetaldehyde and 100 parts of aprotic solvent into a three-necked flask. Under nitrogen conditions, slowly add 40 parts of dopamine and 1 part of glacial acetic acid. Heat the reaction system to 110°C and keep stirring for 10 hours to obtain a bio-based chain extender with dynamic oxime bonds and disulfide bonds, which is Component B.

[0042] Step 4: Mix component A and component B at a weight ratio of 100:10 at room temperature until homogeneous. Then add 15 parts inorganic filler, 3 parts toughening agent, 1 part adhesion promoter, and 0.5 parts defoamer to obtain the targeted self-healing polyurethane sealant.

[0043] Example 3

[0044] A method for preparing a targeted self-healing polyurethane sealant includes the following steps:

[0045] Step 1: Preparation of dopamine-modified nano-Fe3O4: Nano-Fe3O4 particles were prepared using a co-precipitation method. The co-precipitation method mainly involves the precipitation of Fe3O4 particles. 2+ / Fe 3+ An alkaline environment was provided by adding alkali to the salt solution, ultimately generating nano-Fe3O4 particles. Twenty parts of nano-Fe3O4 particles were weighed and pre-dried in an oven at 120°C for 1 hour. They were then ultrasonically dispersed in 100 parts of an aprotic solvent. Under nitrogen protection and mechanical stirring, 5 parts of aminopropyltriethoxysilane were added dropwise to the dispersion, and the mixture was heated to 80°C and refluxed for 24 hours to obtain aminated nano-Fe3O4. The system was then heated to 110°C, and 15 parts of dopamine and 2 parts of glacial acetic acid were slowly added under nitrogen protection, with continuous stirring for 12 hours to obtain dopamine-modified nano-Fe3O4.

[0046] Step 2, Preparation of Component A: Weigh 100 parts of bio-based polyol and heat it at 120℃ to remove water for 2 hours. Then lower the temperature to 80℃ and add 200 parts of polyisocyanate under nitrogen protection. Stir continuously for 1 hour. Then lower the temperature to 60℃ and add 20 parts of aprotic solvent and 3 parts of dopamine-modified nano-iron oxide particles. Stir continuously for 1 hour to obtain modified polyurethane prepolymer, which is Component A.

[0047] Step 3, Preparation of Component B: Weigh 30 parts of disulfide dialkyl diacetaldehyde and 100 parts of aprotic solvent into a three-necked flask. Under nitrogen conditions, slowly add 50 parts of dopamine and 2 parts of glacial acetic acid. Heat the reaction system to 110°C and keep stirring for 10 hours to obtain a bio-based chain extender with dynamic oxime bonds and disulfide bonds, which is Component B.

[0048] Step 4: Mix component A and component B at a weight ratio of 100:20 at room temperature until homogeneous. Then add 20 parts of inorganic filler, 10 parts of toughening agent, 3 parts of adhesion promoter, and 1 part of defoamer to obtain the targeted self-healing polyurethane sealant.

[0049] Comparative Example 1

[0050] Step 1, Preparation of Component A: Weigh 80 parts of bio-based polyol and heat it at 120℃ to remove water for 2 hours. Then lower the temperature to 80℃ and add 150 parts of polyisocyanate under nitrogen protection. Stir continuously for 1 hour. Then lower the temperature to 60℃ and add 10 parts of aprotic solvent. Stir continuously for 1 hour to obtain polyurethane prepolymer, which is Component A.

[0051] Step 2, Preparation of Component B: Weigh 20 parts of dithiodialkyl diacetaldehyde and 100 parts of aprotic solvent into a three-necked flask, slowly add 1 part of glacial acetic acid under nitrogen, heat the reaction system to 110°C and keep stirring continuously for 10 hours to obtain the chain extender, which is Component B.

[0052] Step 3: Mix component A and component B at a weight ratio of 100:10-20 at room temperature until homogeneous. Then add 15 parts inorganic filler, 3 parts toughening agent, 1 part adhesion promoter, and 0.5 parts defoamer to obtain polyurethane sealant.

[0053] Comparative Example 2

[0054] Step 1, Preparation of Component A: Weigh 80 parts of bio-based polyol and heat it at 120℃ to remove water for 2 hours. Then lower the temperature to 80℃ and add 150 parts of polyisocyanate under nitrogen protection. Stir continuously for 1 hour. Then lower the temperature to 60℃, add 1 part of dopamine and 10 parts of aprotic solvent and stir continuously for 1 hour to obtain the modified polyurethane prepolymer, which is Component A.

[0055] Step 2, Preparation of Component B: Weigh 20 parts of dithiodialkyl diacetaldehyde and 100 parts of aprotic solvent into a three-necked flask, slowly add 1 part of glacial acetic acid under nitrogen, heat the reaction system to 110°C and keep stirring continuously for 10 hours to obtain the chain extender, which is Component B.

[0056] Step 3: Mix component A and component B at a weight ratio of 100:10-20 at room temperature until homogeneous. Then add 15 parts inorganic filler, 3 parts toughening agent, 1 part adhesion promoter, and 0.5 parts defoamer to obtain polyurethane sealant.

[0057] Table 1. Test Results

[0058]

[0059] In Example 1, component A was a polyurethane prepolymer modified with nano-ferric oxide. Examples 2 and 3 involved modifying the polyurethane prepolymer with dopamine-modified nano-ferric oxide. Comparative Example 1 did not use dopamine or nano-ferric oxide. Comparative Example 2 used a polyurethane prepolymer modified with dopamine but not with nano-ferric oxide. According to the specific parameters in Table 1, the sealant modified with nano-ferric oxide significantly shortened the repair time compared to Comparative Examples 1 and 2, while also improving its mechanical properties and repair rate. Furthermore, the sealant modified with dopamine-modified nano-ferric oxide further shortened the repair time. The higher heat generated at the fracture point by nano-ferric oxide allows for precise self-repair, thus reducing the repair time.

[0060] Under magnetic induction heating at 70℃, polyurethane sealants with added iron(III) oxide (Fe3O4) exhibit significantly shorter self-healing times compared to the unadded group, while also demonstrating higher tensile strength and elongation at break. This performance improvement is attributed to the surface modification of Fe3O4 by dopamine, which effectively prevents particle agglomeration, ensuring uniform dispersion within the polymer matrix. This allows for more efficient conversion of magnetic field energy into heat energy, while also enhancing the material structure and repair efficiency. This invention achieves "on-demand" and "precise" triggering of the self-healing process, improving the sealant's stability, adhesion, crack resistance, and aging resistance at high temperatures.

[0061] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A targeted self-healing polyurethane sealant, comprising component A and component B, characterized in that, Component A is a modified polyurethane prepolymer, and its raw materials include polyisocyanate, bio-based polyol, nano-iron oxide, and aprotic solvent; Component B includes a chain extender.

2. The targeted self-healing polyurethane sealant according to claim 1, characterized in that: The nano-ferric oxide is made by modifying nano-ferric oxide with dopamine.

3. The targeted self-healing polyurethane sealant according to claim 2, characterized in that: Component B includes a modified chain extender, and the raw materials include dithiodialkyl diacetaldehyde, an aprotic solvent, dopamine, and glacial acetic acid.

4. The targeted self-healing polyurethane sealant according to claim 3, characterized in that: The weight ratio of components A and B is 100 parts: 10-20 parts.

5. The targeted self-healing polyurethane sealant according to claim 4, characterized in that: The raw material weight ratio of component A is as follows: modified polyurethane prepolymer, including 150-200 parts of polyisocyanate, 80-100 parts of bio-based polyol, 1-3 parts of modified nano-iron oxide, and 10-20 parts of aprotic solvent.

6. The targeted self-healing polyurethane sealant according to claim 5, characterized in that: The raw material weight ratio of component B modified chain extender is: 20-30 parts dithiodialkyl diacetaldehyde, 100 parts aprotic solvent, 40-50 parts dopamine and 1-2 parts glacial acetic acid.

7. The targeted self-healing polyurethane sealant according to claim 6, characterized in that: Component B also includes auxiliary agents: 15-20 parts; inorganic fillers: 3-10 parts; toughening agents: 1-3 parts; adhesion promoters: 0.5-1 parts; and defoamers.

8. The method for preparing the targeted self-healing polyurethane sealant according to claim 7, characterized in that, Includes the following steps: Step 1, Preparation of Component A: The bio-based polyol is heated to remove water, polyisocyanate is added and stirred continuously, and then aprotic solvent and dopamine-modified nano-iron oxide particles are added and stirred continuously to obtain modified polyurethane prepolymer, which is Component A. Step 2, Preparation of Component B: Dopamine and glacial acetic acid are slowly added to disulfide dialkyl diacetaldehyde and aprotic solvent under nitrogen atmosphere. The reaction system is heated and continuously stirred to obtain a bio-based chain extender with dynamic oxime bonds and disulfide bonds, which is Component B. Step 3: Mix components A and B evenly at room temperature, then add inorganic fillers, toughening agents, adhesion promoters, and defoamers to obtain targeted self-healing polyurethane sealant.

9. A method for preparing the targeted self-healing polyurethane sealant according to claim 8, characterized in that, Preparation of dopamine-modified nano-ferric oxide: in Fe 2+ / Fe 3+ A base was added to a salt solution to generate nano-Fe3O4 particles. The nano-Fe3O4 particles were pre-dried and ultrasonically dispersed in an aprotic solvent. Under nitrogen protection, the mixture was stirred, and aminopropyltriethoxysilane was added dropwise to the dispersion. The mixture was then heated and refluxed to obtain aminated nano-Fe3O4. The system was then heated, and dopamine and glacial acetic acid were slowly added under nitrogen protection while stirring continuously to obtain dopamine-modified nano-Fe3O4.

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