Waterborne polyurethane as well as preparation method and application thereof

Abstract

The invention relates to waterborne polyurethane as well as a preparation method and application thereof. The waterborne polyurethane is prepared from the following raw materials: diisocyanate, polyol, a chain extender, gallic acid, a salt-forming agent and a metal organic framework, the metal organic framework is composed of a metal center and an organic ligand; the metal center comprises copper and / or zinc; the organic ligand comprises an organic matter containing carbonyl and hydroxyl. The gallic acid and the metal organic framework are introduced into the preparation raw materials of the waterborne polyurethane to synergistically improve the mechanical strength and the self-healing performance of the material, and meanwhile, the waterborne polyurethane is endowed with antibacterial ability, so that the waterborne polyurethane can meet the application requirements of more fields.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a waterborne polyurethane and a preparation method and application thereof. Background Art

[0002] Polyurethanes with different molecular structures are widely used in various fields of daily life, including coatings, composite materials, adhesives, biomedical materials, and flexible and rigid foams. However, with environmental problems becoming increasingly serious, traditional solvent-based polyurethanes usually contain a large amount of organic solvents and residual isocyanate monomers, which are harmful to the environment and human body and do not conform to the concept of green material development. In contrast, waterborne polyurethanes use water as a dispersion medium, reducing or eliminating the use of organic solvents, and have good flexibility, elasticity and wear resistance, can withstand large mechanical stress and deformation, have a certain tolerance to a variety of chemicals (such as oils, acids, alkalis, etc.), and are suitable for various harsh environments. Therefore, they are more and more widely used in various industrial fields. However, in actual applications, waterborne polyurethane coatings are easily affected by the external environment, and microcracks and other phenomena occur during long-term use, which will lead to a decrease in the protective performance of the coating and even cause corrosion of the substrate under the coating.

[0003] In order to solve the above problems, the prior art proposes a waterborne polyurethane coating with self-healing ability, which mainly modifies the waterborne polyurethane by the following two methods: one is a physical modification method of directly adding a self-healing agent, a photosensitive dye, a photoinitiator or a microcapsule, namely, external healing modification; the other is a direct chemical modification of the waterborne polyurethane system, such as introducing a dynamic bond into the waterborne polyurethane system, namely, internal healing modification. Compared with external healing modification, internal healing modification has the advantages of simple preparation process, no need for a repair agent, and repeatable healing, so it is widely used. However, internal healing modification usually requires the molecular chain to have good dynamics, so the mechanical properties of the obtained coating will be significantly reduced, and it is impossible to take into account both high self-healing efficiency and good mechanical properties.

[0004] On the other hand, due to the characteristics of polyurethane itself, its coating has a certain promoting effect on the growth of microorganisms, which may cause bacterial growth, which is not conducive to its application in the biological or food fields, and the existing self-healing waterborne polyurethane coatings have not solved this problem. At the same time, it has been found in practice that if general antimicrobial agents are directly added to existing self-healing waterborne polyurethane coatings, it will be difficult for the antimicrobial agents to combine evenly and stably with the coating, thus failing to achieve a good application effect.

[0005] Therefore, how to develop a polyurethane material with excellent self-healing properties, high mechanical strength and good antibacterial effect has become a problem that needs to be solved urgently. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a waterborne polyurethane and a preparation method and application thereof. By introducing gallic acid and metal organic framework (MOFs) materials into the structure of the waterborne polyurethane, the waterborne polyurethane is endowed with self-healing and antibacterial capabilities, while improving the mechanical properties of the waterborne polyurethane, thereby solving the problems of poor mechanical properties, high cost, inability to self-heal, and single function of waterborne polyurethane materials in the prior art.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a waterborne polyurethane, wherein the raw materials for preparing the waterborne polyurethane include the following components: diisocyanate, polyol, chain extender, gallic acid, salt-forming agent and metal organic framework;

[0009] The metal organic framework is composed of a metal center and an organic ligand;

[0010] The metal center includes copper and / or zinc;

[0011] The organic ligand includes organic substances containing carbonyl and hydroxyl groups.

[0012] The waterborne polyurethane preparation raw materials provided by the present invention include gallic acid, which has a rigid structure that improves the thermal stability and mechanical properties of polyurethane, and can show good repair performance after a certain treatment through the thermal response of the dynamic covalent bond phenol-carbamate bond, giving the waterborne polyurethane self-healing ability, and the bio-based material is more environmentally friendly and safe. For the MOFs used in the present invention, it is centered on copper and zinc, provides certain antibacterial properties, and forms coordination bonds with hydroxyl groups at the same time, and improves the compatibility of components by generating non-covalent interactions, which is conducive to the polymerization reaction. The MOFs use organic matter containing carbonyl and hydroxyl groups as ligands, can react with isocyanate components to form covalent bonds, and are embedded in polyurethane molecular segments, so that it can maintain long-term effectiveness; the part of the metal organic framework that is not connected to the segment can be well dispersed in the waterborne polyurethane, and hydrogen bonds are generated with the waterborne polyurethane molecular chain, and have a synergistic effect with the dynamic covalent bond, and jointly promote the self-healing performance of the material. Therefore, the present invention combines the metal organic framework through covalent and non-covalent effects, integrates it into the waterborne polyurethane (WPU), combines the advantages of both, and improves the performance of the composite material. The rigid structure of MOFs improves the strength and hardness of WPU while maintaining its flexibility and elasticity. The addition of MOFs also improves the heat resistance of WPU, making it stable at higher temperatures.

[0013] Preferably, the raw materials for preparing the waterborne polyurethane include the following components, measured in parts by weight: 25-35 parts of diisocyanate (for example, 26 parts, 28 parts, 30 parts, 32 parts or 34 parts, etc.), 40-60 parts of polyol (for example, 42 parts, 45 parts, 48 ​​parts, 50 parts, 52 parts, 55 parts or 58 parts, etc.), 4-12 parts of chain extender (for example, 5 parts, 7 parts, 9 parts or 11 parts, etc.), 0. 2-0.8 parts (for example, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts or 0.7 parts, etc.), 3-5 parts of salt-forming agent (for example, 3.2 parts, 3.5 parts, 3.8 parts, 4 parts, 4.2 parts, 4.5 parts or 4.8 parts, etc.), 0.1-3 parts of metal organic framework (for example, 0.2 parts, 0.5 parts, 0.8 parts, 1 parts, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts or 2.5 parts, etc.).

[0014] In the present invention, a more excellent application effect can be achieved by using a specific content of gallic acid and metal organic framework. When the amount of gallic acid used is too large, the self-healing performance will deteriorate due to the large rigidity of the system at this time; when the amount of gallic acid used is too small, the mechanical strength of the obtained waterborne polyurethane is reduced and the self-healing ability is insufficient. When the MOF content is too small, the interaction between MOF and the WPU matrix is ​​weak, which is not enough to provide significant physical cross-linking points and cannot fully form effective interfacial bonding, thereby limiting the significant improvement of the hardness and modulus of the polyurethane, and limiting the role of MOF in enhancing mechanical properties. When the MOF content is too large, too many MOF particles tend to agglomerate in the polyurethane matrix to form large particles or aggregates. This aggregation phenomenon will cause stress concentration in the material, thereby reducing the mechanical properties of WPU.

[0015] Preferably, the diisocyanate includes any one of hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate or toluene diisocyanate, or a combination of at least two thereof.

[0016] Preferably, the polyol includes any one of polytetramethylene glycol, polyoxypropylene glycol, polyethylene glycol or polyhexylene adipate glycol, or a combination of at least two thereof.

[0017] Preferably, the weight average molecular weight of the polyol is 500-4000 g / mol, for example, 800 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol or 3500 g / mol.

[0018] Preferably, the chain extender includes a hydrophilic chain extender and a small molecule chain extender.

[0019] Preferably, the mass ratio of the hydrophilic chain extender to the small molecule chain extender is (0.5-10):1, wherein the specific value of (0.5-10) can be, for example, 1, 2, 3, 4, 5, 6 or 8.

[0020] Preferably, the hydrophilic chain extender includes any one of 2,2-bis(hydroxymethyl)propionic acid (DMPA), 2,2-dihydroxymethylbutyric acid or polyoxyethylene ether (hydrophilic chain extender N120) or a combination of at least two thereof.

[0021] Preferably, the small molecule chain extender includes 1,4-butanediol and / or 1,6-hexanediol.

[0022] Preferably, the salt-forming agent includes any one of sodium hydroxide, triethylamine or hydrochloric acid.

[0023] Preferably, the raw materials for preparing the waterborne polyurethane further include 0.05-0.15 parts of a catalyst, for example, 0.06 parts, 0.08 parts, 0.1 parts, 0.12 parts or 0.14 parts, etc., by weight.

[0024] Preferably, the catalyst includes any one of an organic tin catalyst, a zinc-based catalyst, an organic antimony catalyst, and a bismuth-based catalyst, or a combination of at least two of them.

[0025] Preferably, the catalyst comprises stannous octoate and / or dibutyltin dilaurate.

[0026] Preferably, the organic ligand includes any one of terephthalic acid, trimellitic acid, 2,6-naphthalene dicarboxylic acid or 1,3,5-benzene trimellitic acid, or a combination of at least two thereof.

[0027] Preferably, the metal organic framework comprises any one of Cu-MOF-74, Zn-MOF-5, MOF-119 or Cu-BTC, or a combination of at least two thereof.

[0028] The metal organic framework used in the present invention can be prepared by methods in the prior art.

[0029] Exemplarily, the Cu-MOF-74 is prepared by a simple hydrothermal synthesis method, and the synthesis method is as follows:

[0030] (1) A mixture of terephthalic acid and copper (II) nitrate trihydrate in a mass ratio of 1:(2-10) (e.g., 1:3, 1:4, 1:5, 1:6 or 1:8, etc.) is added to a mixed solution of N,N-dimethylformamide and methanol in a volume ratio of (5-15):1 (e.g., 1:6, 1:8, 1:10, 1:12 or 1:14, etc.), wherein the concentration of terephthalic acid in the mixed solution is 5-10 mg / mL (e.g., 5.5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL or 9 mg / mL, etc.). The suspension is then stirred at room temperature to obtain a dark green homogeneous solution;

[0031] (2) The solution is placed in a high-pressure hydrothermal autoclave. The autoclave is then sealed and hydrothermaled in a forced air drying oven at 100-150°C (e.g., 105°C, 110°C, 120°C, 130°C, or 140°C, etc.) for 12-48h (e.g., 16h, 20h, 24h, 28h, 32h, 36h, or 40h, etc.). Thereafter, the hydrothermal reactor is naturally cooled to room temperature;

[0032] (3) First wash with N,N-dimethylformamide three times, then replace with methanol, and dry at 80-120°C (for example, 85°C, 90°C, 95°C, 100°C or 110°C, etc.) for 6-24h (for example, 8h, 10h, 12h, 16h or 20h, etc.) to obtain blue solid powder Cu-MOF-74.

[0033] Preferably, the raw materials for preparing the waterborne polyurethane further include 5-15 parts of solvent, for example, 6 parts, 7 parts, 8 parts, 10 parts or 12 parts, etc., by weight.

[0034] Preferably, the solvent includes any one of acetone, butanone, N,N-dimethylacetamide or N,N-dimethylformamide, or a combination of at least two thereof.

[0035] In a second aspect, the present invention provides a method for preparing the waterborne polyurethane as described in the first aspect, the preparation method comprising the following steps:

[0036] The waterborne polyurethane is obtained by reacting diisocyanate, polyol, chain extender, gallic acid, salt-forming agent, metal organic framework and optional catalyst.

[0037] Preferably, the preparation method comprises the following steps:

[0038] (1) premixing diisocyanate and polyol, adding a hydrophilic chain extender, a catalyst and an optional solvent to obtain a first mixture solution;

[0039] (2) cooling the first mixture solution obtained in step (1), adding a small molecule chain extender, gallic acid and a metal organic framework and mixing them to obtain a second mixture solution;

[0040] (3) cooling the second mixture solution obtained in step (1), adding a salt-forming agent to continue the reaction, and adding water to quench the mixture to obtain the waterborne polyurethane.

[0041] Preferably, the polyol is premixed after being dried.

[0042] Preferably, the drying is performed under vacuum conditions.

[0043] Preferably, the drying time is 6-24 hours, for example, it can be 8 hours, 10 hours, 12 hours, 14 hours, 16 hours or 20 hours.

[0044] Preferably, in step (1), the premixing is carried out in the presence of a protective gas.

[0045] Preferably, the protective gas includes any one of nitrogen, argon or helium, or a combination of at least two of them.

[0046] Preferably, the premix temperature is 70-80°C, for example, 71°C, 73°C, 75°C, 77°C or 79°C.

[0047] Preferably, the premixing time is 1-2.5 h, for example, 1.2 h, 1.5 h, 1.8 h, 2 h or 2.2 h.

[0048] Preferably, the stirring speed of the premix is ​​600-800 r / min, for example, 620 r / min, 650 r / min, 680 r / min, 700 r / min, 720 r / min, 750 r / min or 780 r / min.

[0049] Preferably, in step (2), the cooling temperature is 60-70°C, for example, 61°C, 63°C, 65°C, 67°C or 69°C.

[0050] Preferably, in step (2), the stirring speed for mixing is 600-800 r / min, for example, it can be 620 r / min, 650 r / min, 680 r / min, 700 r / min, 720 r / min, 750 r / min or 780 r / min, etc.

[0051] Preferably, in step (2), the mixing time is 3-5 h, for example, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h or 4.8 h.

[0052] Preferably, in step (3), the cooling temperature is 30-50°C, for example, 32°C, 35°C, 38°C, 40°C, 41°C, 43°C, 45°C, 47°C or 49°C.

[0053] Preferably, in step (3), the time for continuing the reaction is 30-60 min, for example, 35 min, 40 min, 45 min, 50 min or 55 min.

[0054] Preferably, stirring is continued after quenching with water.

[0055] Preferably, the rotation speed of the continued stirring is 1500-1900 r / min, for example, it can be 1550 r / min, 1600 r / min, 1650 r / min, 1700 r / min, 1750 r / min, 1800 r / min or 1850 r / min.

[0056] Preferably, the stirring time is 20-40 min, for example, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min or 38 min.

[0057] Preferably, after continuing stirring, the mixture is allowed to stand for 20-45 min (for example, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 38 min, 40 min or 42 min, etc.) to remove the solvent to obtain the waterborne polyurethane.

[0058] The waterborne polyurethane prepared by the present invention can be cast on a polytetrafluoroethylene plate to prepare a WPU film.

[0059] In a third aspect, the present invention provides a use of the waterborne polyurethane as described in the first aspect in coatings, adhesives, biomedical materials, flexible foams or rigid foams.

[0060] Compared with the prior art, the present invention has at least the following beneficial effects:

[0061] The waterborne polyurethane provided by the present invention exhibits good repair performance by introducing gallic acid to form a dynamic covalent phenol-urethane bond; through the covalent action and non-covalent action of the metal organic framework and the polyurethane molecular chain, on the one hand, synergistic enhancement is formed with the dynamic covalent bond to jointly promote the self-healing performance of the material, while improving its mechanical properties and tensile strength; on the other hand, good antibacterial function is given to the material, and finally the waterborne polyurethane with self-healing and antibacterial functions is obtained, which meets the application needs in multiple fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1The tensile properties of the waterborne polyurethanes obtained in Examples 1-4 and Comparative Example 1;

[0063] Figure 2 The tensile properties of the waterborne polyurethane obtained in Example 1 after self-healing;

[0064] Figure 3 The tensile properties of the waterborne polyurethane obtained in Example 2 after self-healing;

[0065] Figure 4 The tensile properties of the waterborne polyurethane obtained in Example 3 after self-healing;

[0066] Figure 5 The tensile properties of the waterborne polyurethane obtained in Example 4 after self-healing;

[0067] Figure 6 This is a diagram showing the antibacterial effect of the waterborne polyurethane obtained in Examples 1-4 on Staphylococcus aureus;

[0068] Figure 7 This is a diagram showing the antibacterial effect of the waterborne polyurethane obtained in Examples 1-4 on Escherichia coli. DETAILED DESCRIPTION

[0069] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0070] The polyol used in the following examples is polytetrahydrofuran diol (Shanghai MacLean Biochemical Technology Co., Ltd., PTMG-1000), MOF is Cu-MOF-74 obtained in Preparation Example 1, and other materials are commercially available products.

[0071] Preparation Example 1

[0072] A metal organic framework Cu-MOF-74, wherein the metal organic framework is prepared by the following method:

[0073] (1) A mixture of 0.5 g of terephthalic acid and 2.5 g of copper (II) nitrate trihydrate was added to a mixed solution of 54 mL of N,N-dimethylformamide and 6 mL of methanol. The suspension was then stirred at room temperature for 20 min to obtain a dark green homogeneous solution;

[0074] (2) The solution was placed in a 100 mL high pressure hydrothermal autoclave. The autoclave was then sealed and hydrothermaled at 120°C for 24 h in a forced air drying oven. Thereafter, the hydrothermal reactor was naturally cooled to room temperature.

[0075] (3) The product was first washed with N,N-dimethylformamide for three times, then replaced with methanol, and dried at 100 °C for 12 h to obtain a blue solid powder of Cu-MOF-74.

[0076] Example 1

[0077] A waterborne polyurethane is prepared by the following method:

[0078] (1) polytetrahydrofuran diol (PTMG-1000) was dried in a vacuum drying oven at 70°C for 24h; 2.7g of isophorone diisocyanate (IPDI) and 5.4g of the dried polytetrahydrofuran diol were added to a three-necked flask, nitrogen was introduced into the flask, the temperature was raised to 80°C, magnetic stirring was performed at a stirring speed of 600r / min, and the reaction was carried out for 1h;

[0079] 0.48 g of 2,2-bis(hydroxymethyl)propionic acid (DMPA) dissolved in N,N-dimethylacetamide (DMA) and two drops of stannous octoate were added to the dispersion, 9 mL of acetone was added to reduce the viscosity of the solution, and the mixture was stirred at a speed of 600 r / min for 2 h to obtain a first mixture solution;

[0080] (2) cooling the obtained first mixture solution to 65° C., adding 0.03 g of gallic acid (GA), 0.16 g of 1,4-butanediol (BDO) and 0.045 g of Cu-MOF-74, stirring, keeping the stirring speed constant, stirring for 4 h, to obtain a second mixture solution;

[0081] (3) The obtained second mixture solution was cooled to 50° C., 497 μL of triethylamine (TEA) was added and the mixture was stirred continuously at a constant stirring speed for 30 min. After the reaction was completed, the mixture was cooled to room temperature, 25 mL of water was added, and the mixture was stirred at a high speed of 1500 r / min for 30 min. After the reaction was completed, the mixture was left to stand for 15 min. The residual organic solvent was removed by rotary evaporation at 50° C. and 70 r / min to obtain an aqueous polyurethane solution, which was cast on a polytetrafluoroethylene plate and placed at room temperature for 48 h. The solution was then transferred to an oven at 60° C. and dried for 48 h to obtain the aqueous polyurethane solution.

[0082] Example 2

[0083] A waterborne polyurethane, the waterborne polyurethane differs from Example 1 only in that the amount of Cu-MOF-74 is 1%, i.e., 0.09 g of Cu-MOF-74 is added in step (2), and the amounts of other materials and the preparation steps are the same as those in Example 1.

[0084] Example 3

[0085] A waterborne polyurethane, the waterborne polyurethane differs from Example 1 only in that the amount of Cu-MOF-74 is 2%, i.e., 0.18 g of Cu-MOF-74 is added in step (2), and the amounts of other materials and the preparation steps are the same as those in Example 1.

[0086] Example 4

[0087] A waterborne polyurethane, the waterborne polyurethane differs from Example 1 only in that the amount of Cu-MOF-74 is 3%, i.e., 0.27 g of Cu-MOF-74 is added in step (2), and the amounts of other materials and the preparation steps are the same as those in Example 1.

[0088] Example 5

[0089] A waterborne polyurethane, the waterborne polyurethane differs from Example 1 only in that the amount of Cu-MOF-74 is 6%, i.e., 0.54 g of Cu-MOF-74 is added in step (2), and the amounts of other materials and the preparation steps are the same as those in Example 1.

[0090] Comparative Example 1

[0091] A waterborne polyurethane, the waterborne polyurethane differs from Example 1 only in that the amount of Cu-MOF-74 is 0%, that is, Cu-MOF-74 is not added in step (2), and the amounts of other materials and the preparation steps are the same as those in Example 1.

[0092] Comparative Example 2

[0093] A waterborne polyurethane, the waterborne polyurethane differs from Example 1 only in that Cu-MOF-74 is replaced by ZIF-8 of equal mass, and other material amounts and preparation steps are the same as those in Example 1.

[0094] The above waterborne polyurethane was tested as follows:

[0095] (1) Tensile properties:

[0096] According to QB / T2415-1998 test, the samples were cut into dumbbell (2mm×10mm) type specimens through a mold, and tested at an ambient temperature of 25°C and a relative humidity of 65-85%. The tensile strength was measured by a double-column table test system to determine the mechanical properties of the polyurethane film. The stretching rate was 50mm / min, and the measurement result was the average of 3 experiments.

[0097] (2) Hydrophilic properties:

[0098] The affinity of the composite film was determined by the size of the contact angle. The test was conducted at an ambient temperature of 25°C, and the average value of three experiments was taken as the final result.

[0099] (3) Self-healing performance:

[0100] First, a dumbbell-shaped specimen of a specific size was prepared from the dry polyurethane film using a cutter, and then the polyurethane film specimen was cut using a clean razor blade. Then, a certain force was used to bring the fracture surfaces of the two half films into close contact, and then they were transferred to a 60°C constant temperature oven and kept warm for 24 hours. In order to further study the self-healing properties of the modified WPU, its strain recovery was quantitatively evaluated using a universal tensile test. The self-healing efficiency (η) of the studied specimens heated at different temperatures for different times was defined as:

[0101]

[0102] σ(heal) and σ(original) are the tensile strain and tensile strength of the repaired and original specimens, respectively.

[0103] The test results are summarized in Table 1.

[0104] Table 1

[0105] Elongation at break (%) Tensile strength(MPa) Water contact angle (°) Repair efficiency (%) Example 1 867.9 11.9 79.6 84 Example 2 850.6 16.7 85.1 85.4 Example 3 669.1 22.5 91.5 88.4 Example 4 620.4 28 95.6 90 Example 5 882.9 10.8 72.9 83.2 Comparative Example 1 887.7 7.4 68.5 83.7 Comparative Example 2 896.3 8.5 67.9 80.3

[0106] Combined with Table 1 Figure 1 , Figure 2 It can be seen that the waterborne polyurethane provided by the present invention has excellent mechanical properties and self-healing effects by introducing gallic acid and metal organic framework, with a tensile strength of ≥10.8MPa and a repair efficiency of ≥83.2%.

[0107] By comparing Example 1 with Example 5, it can be seen that when an excessive amount of metal organic frame is added, the MOF material agglomerates in the polyurethane matrix due to its own aggregation effect to form large particles or aggregates. This aggregation phenomenon can cause stress concentration in the material, the interfacial bonding with the polyurethane matrix may deteriorate, and the interfacial interaction is weakened, resulting in a decrease in stress transfer efficiency, thereby reducing the mechanical properties of WPU. And MOF itself is rigid, and when its content increases too much, it will cause the flexibility of the WPU material to decrease, making it show higher brittleness and affecting the self-healing properties of the sample. The present invention further improves the mechanical properties and self-healing properties of the material by further regulating the content of MOF.

[0108] By comparing Examples 1-5 with Comparative Example 1, it can be seen that the present invention improves the hydrophilicity of waterborne polyurethane by adding a metal organic framework, and its repair efficiency after heating is higher. At the same time, the tensile strength is significantly enhanced, and the mechanical strength of the material is improved.

[0109] By comparing Example 1 with Comparative Example 2, it can be seen that the specific type of MOF material added in the present invention can better improve the mechanical properties and self-healing properties of waterborne polyurethane. This is mainly because the MOF defined in the present invention has better polarity, stronger interfacial interaction (polar functional groups such as hydroxyl and carbonyl groups are contained in the organic ligands), and uniform dispersion ability in the material, which can more effectively enhance the mechanical properties of WPU. Other MOF materials, such as ZIF-8, have poor physical crosslinking effects and their structures are relatively rigid. Excessive addition will increase the brittleness of the material, reduce the specific gravity of the soft link, and reduce the self-healing properties of the material.

[0110] (4) Antibacterial properties

[0111] The antibacterial performance of the sample was characterized by the inhibition zone test. The specific operation is as follows:

[0112] Bacterial inoculation: Prepare the cultured bacterial strain into a suitable concentration suspension (usually adjusted to 0.5 concentration according to the McFarland standard, i.e. about 1×10^ 8 CFU / mL). Use a sterile cotton swab to evenly spread the bacterial suspension on the surface of the agar medium to ensure that the bacteria are evenly distributed on the entire agar surface.

[0113] Sample processing: Cut the sample into discs with a diameter of 1 cm, sterilize them under ultraviolet light for 24 hours, and then place them on the surface of the agar culture medium.

[0114] Cultivation: Place the culture dish inoculated with bacteria and samples in an incubator at 37°C and incubate for 18-24 hours to allow the bacteria to fully grow on the culture medium.

[0115] The test results are as follows Figure 6 , Figure 7 As shown, the size of the inhibition zone is related to the degree of inhibition, and the larger the radius, the better the antibacterial performance. The waterborne polyurethane provided by the present invention has excellent antibacterial performance, which is due to the MOF material used gradually releasing metal ions in an aqueous environment. Metal ions can bind to proteins on the cell membrane of bacteria, thereby destroying the enzyme activity and protein function of bacteria, interacting, destroying the integrity of the cell membrane, causing leakage of cell contents and ultimately killing bacteria. Metal ions can effectively inhibit the growth and reproduction of bacteria with this mechanism in bacterial cells. The surface of the MOF material has abundant active sites, which can interact with the phospholipid bilayer in the bacterial cell membrane, leading to the destruction of the cell membrane and cell death. The MOF material can catalyze the generation of reactive oxygen (such as hydroxyl radicals, hydrogen peroxide, etc.) under illumination or other conditions. These reactive oxygen can oxidize the cell membrane, protein and DNA of bacteria, leading to bacterial death.

[0116] In summary, the present invention introduces gallic acid and metal organic framework into the preparation raw materials of polyurethane to obtain water-based polyurethane with excellent mechanical properties, self-healing and antibacterial functions, so that it can meet the performance requirements of multiple fields and expand the application field of polyurethane.

[0117] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A waterborne polyurethane, characterized in that: The raw materials for preparing the waterborne polyurethane include the following components: diisocyanate, polyol, chain extender, gallic acid, salt-forming agent and metal organic framework; The metal organic framework is composed of a metal center and an organic ligand; The metal center includes copper and / or zinc; The organic ligand includes organic substances containing carbonyl and hydroxyl groups.

2. The aqueous polyurethane according to claim 1, characterized in that The raw materials for preparing the waterborne polyurethane include the following components in parts by weight: 25-35 parts of diisocyanate, 40-60 parts of polyol, 4-12 parts of chain extender, 0.2-0.8 parts of gallic acid, 3-5 parts of salt-forming agent, and 0.1-3 parts of metal organic framework.

3. The aqueous polyurethane according to claim 1 or 2, characterized in that: The diisocyanate includes any one of hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate or toluene diisocyanate, or a combination of at least two thereof; Preferably, the polyol comprises any one of polytetramethylene glycol, polyoxypropylene glycol, polyethylene glycol or polyhexanediol adipate, or a combination of at least two thereof; Preferably, the weight average molecular weight of the polyol is 500-4000 g / mol.

4. The aqueous polyurethane according to any one of claims 1 to 3, characterized in that The chain extender includes a hydrophilic chain extender and a small molecule chain extender; Preferably, the mass ratio of the hydrophilic chain extender to the small molecule chain extender is (0.5-10):1; Preferably, the hydrophilic chain extender includes any one of 2,2-bis(hydroxymethyl)propionic acid, 2,2-dihydroxymethylbutyric acid or polyoxyethylene ether or a combination of at least two thereof; Preferably, the small molecule chain extender includes 1,4-butanediol and / or 1,6-hexanediol.

5. The waterborne polyurethane according to any one of claims 1 to 4, characterized in that: The salt-forming agent includes any one of sodium hydroxide, triethylamine or hydrochloric acid; Preferably, the raw materials for preparing the waterborne polyurethane further include 0.05-0.15 parts of a catalyst, by weight; Preferably, the catalyst includes any one of an organic tin catalyst, a zinc-based catalyst, an organic antimony catalyst, and a bismuth-based catalyst, or a combination of at least two of them.

6. The aqueous polyurethane according to any one of claims 1 to 5, characterized in that: The organic ligand includes any one of terephthalic acid, 2,6-naphthalene dicarboxylic acid or 1,3,5-benzene trimeric acid or a combination of at least two thereof; Preferably, the metal organic framework comprises any one of Cu-MOF-74, Zn-MOF-5, MOF-119 or Cu-BTC, or a combination of at least two thereof.

7. A method for preparing the waterborne polyurethane according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: The waterborne polyurethane is obtained by reacting diisocyanate, polyol, chain extender, gallic acid, salt-forming agent, metal organic framework and an optional catalyst.

8. The preparation method according to claim 7, characterized in that: The preparation method comprises the following steps: (1) premixing diisocyanate and polyol, adding a hydrophilic chain extender, a catalyst and an optional solvent to obtain a first mixture solution; (2) cooling the first mixture solution obtained in step (1), adding a small molecule chain extender, gallic acid and a metal organic framework and mixing them to obtain a second mixture solution; (3) cooling the second mixture solution obtained in step (1), adding a salt-forming agent to continue the reaction, and adding water to quench the mixture to obtain the waterborne polyurethane.

9. The preparation method according to claim 8, characterized in that: In step (1), the premixing is carried out in the presence of a protective gas; Preferably, the protective gas comprises any one of nitrogen, argon or helium, or a combination of at least two thereof; Preferably, the premix temperature is 70-80°C; Preferably, the premixing time is 1-2.5h; Preferably, the stirring speed of the premix is ​​600-800 r / min; Preferably, in step (2), the cooling temperature is 60-70°C; Preferably, in step (2), the stirring speed of the mixing is 600-800 r / min; Preferably, in step (2), the mixing time is 3-5 hours; Preferably, in step (3), the cooling temperature is 30-50°C; Preferably, in step (3), the reaction time is 30-60 min; Preferably, stirring is continued after quenching with water; Preferably, the rotation speed of the continued stirring is 1500-1900 r / min; Preferably, the stirring time is 20-40 minutes; Preferably, the mixture is allowed to stand for 20-45 minutes after continued stirring to remove the solvent to obtain the waterborne polyurethane.

10. Use of the waterborne polyurethane according to any one of claims 1 to 6 in coatings, adhesives, biomedical materials, flexible foams or rigid foams.

Images