Vegetable oil-based room-temperature water-induced self-healing polyurethane elastomer and preparation method thereof

Abstract

The invention discloses a vegetable oil-based room-temperature water-induced self-healing polyurethane elastomer and a preparation method thereof. The elastomer is prepared by taking polytetramethylene ether glycol and tung oil glycol as soft segments, isophorone diisocyanate as a hard segment, dimethylolpropionic acid as a hydrophilic chain extender and 3-aminophenylboronic acid as an end-capping reagent. Polytetramethylene ether glycol and tung oil glycol are used as soft segments, isophorone diisocyanate is used as a hard segment, dimethylolpropionic acid is used as a hydrophilic chain extender, 3-aminophenylboronic acid is used for blocking, then triethylamine is used for neutralization, and a waterborne polyurethane material with high-density crosslinking sites is synthesized. The material has good mechanical properties and fracture toughness, the tensile strength of the polyurethane film can reach 6.94 MPa, the elongation at break can reach 790.1%, and the film has good rebound resilience.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a plant oil-based room temperature water-induced self-healing polyurethane elastomer and a preparation method thereof. Background Art

[0002] Waterborne polyurethane is a type of polyurethane material that uses water as a solvent or dispersion medium. Compared with traditional solvent-based polyurethane, waterborne polyurethane has received widespread attention due to its environmental friendliness and safety. Traditional solvent-based polyurethane often uses volatile organic compounds (VOCs) as solvents. These organic compounds are released into the environment during use and drying, causing air pollution and may have adverse effects on human health. Therefore, the development of waterborne polyurethane materials to reduce VOC emissions and improve environmental performance has become an important topic in materials science and industrial technology.

[0003] The main components of waterborne polyurethane include polyether or polyester diol, isocyanate and water. Through a specific synthesis process, these components form a stable emulsion in the water phase, so that the polyurethane can exist in the water phase. During the preparation of waterborne polyurethane, isocyanate reacts with polyether or polyester diol containing hydrophilic groups to form a polyurethane with water-dispersibility. Due to the presence of the water phase, waterborne polyurethane has better environmental adaptability, lower odor and higher safety, which makes it widely used in coatings, adhesives, textile finishing, automotive interiors and other fields.

[0004] In recent years, waterborne polyurethane has gradually become a mainstream product in the market under the background of increasingly stringent environmental regulations. Traditional solvent-based polyurethane has been gradually restricted or eliminated by many countries and regions due to its high VOC emissions and potential harm to the environment. Waterborne polyurethane has become the choice of new materials in many industrial fields due to its significant environmental advantages. For example, in architectural coatings, waterborne polyurethane can not only effectively reduce VOC emissions, but also provide excellent weather resistance, adhesion and mechanical properties. In the automotive industry, waterborne polyurethane is widely used in body coatings and interior materials, providing a more environmentally friendly solution for automobiles.

[0005] The research and development of waterborne polyurethanes still faces some challenges. First, the performance of waterborne polyurethanes needs to be comparable to that of traditional solvent-based polyurethanes, including hardness, abrasion resistance, chemical resistance, and gloss. Second, the production process of waterborne polyurethanes needs to overcome the stability problem of the polymerization reaction in the water phase to ensure the quality and stability of the final product. In addition, cost control of waterborne polyurethanes is also a key issue. The R&D team needs to continuously optimize the formula and production process to achieve the best balance between economy and performance.

[0006] In short, as an environmentally friendly and efficient new material, waterborne polyurethane has broad research and application prospects. With the advancement of technology and the improvement of environmental protection requirements, waterborne polyurethane will show its unique advantages and value in more fields. In order to meet market demand and improve the performance of waterborne polyurethane, the research and development of various innovative technologies and new materials has become an important development direction.

[0007] Plant oils provide a wide range of chemical structures and various reaction sites (epoxy groups, unsaturated groups, and ester groups), which can be chemically modified into various customized polyols to promote their application in polyurethanes. In previous studies on bio-based polyurethanes, polyurethane addition polymerization was mostly carried out using hydroxyl-rich plant oils (such as castor oil) or direct modification of other oils (such as epoxy-ring opening, thiol-olefin click chemistry). The modification strategies were very limited, and the functionality was not studied in depth. In addition, the mechanical properties or thermal properties of some bio-based polyurethanes are weak and do not have practical application value.

[0008] The Chinese patent application document with publication number CN115947922A reacts diisocyanate with deoxythymidine, and then adds polyether polyol, 2,2-dihydroxymethyl propionic acid and solvent. Among them, by introducing structures such as deoxythymidine, the prepared waterborne polyurethane elastomer has self-repairing ability. However, there may be situations where the mechanical properties are not outstanding enough, water resistance or other properties are poor. For example, its stability in certain specific environments may be relatively weak, or its performance in strength, hardness, etc. may not be particularly excellent.

[0009] At present, the preparation methods and performance research of plant oil-derived self-healing elastomers at home and abroad are still immature, and there is little functional development. There is even less functional research on plant oil-based room temperature self-healing waterborne polyurethanes. Summary of the invention

[0010] The technical problem to be solved by the present invention is how to improve the mechanical properties of bio-based polyurethane.

[0011] The present invention solves the above technical problems through the following technical means:

[0012] A plant oil-based room temperature water-induced self-healing polyurethane elastomer is prepared with polytetramethylene ether glycol and tung oil glycol as soft segments, isophorone diisocyanate as hard segments, dimethylol propionic acid as a hydrophilic chain extender, and 3-aminophenylboronic acid as a capping agent;

[0013] Wherein, the structural formula of the tung oil glycol is

[0014] Preferably, the number average molecular weight of the polytetramethylene ether glycol is 2000 g / mol.

[0015] Preferably, the molar ratio of the polytetramethylene ether glycol to tung oil glycol is 1:1.

[0016] Preferably, the molar ratio of the soft segment to the hard segment is 15-19:32.

[0017] Preferably, the molar ratio of isophorone diisocyanate to dimethylolpropionic acid is 32:10.

[0018] Preferably, the ratio of the total mole number of the polytetramethylene ether glycol and the tung oil glycol to the mole number of 3-aminophenylboronic acid is 15-19:2-10.

[0019] Preferably, the molar ratio of the polytetramethylene ether glycol, tung oil glycol and 3-aminophenylboronic acid is 7.5-9.5:7.5-9.5:2-10.

[0020] Preferably, the molar ratio of polytetramethylene ether glycol, tung oil glycol and 3-aminophenylboronic acid is 8.5:8.5:6.

[0021] Preferably, the molar ratio of the polytetramethylene ether glycol, tung oil glycol, isophorone diisocyanate, dimethylol propionic acid and 3-aminophenylboronic acid is 7.5-9.5:7.5-9.5:32:10:2-10.

[0022] Preferably, the molar ratio of the polytetramethylene ether glycol, tung oil glycol, isophorone diisocyanate, dimethylol propionic acid and 3-aminophenylboronic acid is 8.5:8.5:32:10:6.

[0023] Preferably, during the preparation process, dibutyltin dilaurate is used as a catalyst.

[0024] The present invention also proposes a method for preparing the plant oil-based room temperature water-induced self-healing polyurethane elastomer, comprising the following steps: mixing polytetramethylene ether glycol and tung oil glycol, stirring at a constant temperature under a nitrogen atmosphere, adding isophorone diisocyanate and dibutyltin dilaurate to react, adding dimethylolpropionic acid and dibutyltin dilaurate to react, adding 3-aminophenylboric acid solution after the reaction of dimethylolpropionic acid is completed, adding dibutyltin dilaurate to react, adding triethylamine neutralization solution after the reaction is completed, adding water to stir and emulsify, rotary evaporation to obtain an aqueous polyurethane solution, and removing water to obtain the plant oil-based room temperature water-induced self-healing polyurethane elastomer.

[0025] Preferably, the temperature of the constant temperature stirring is 75°C.

[0026] Preferably, the reaction temperature is 75° C. and the reaction time is 3 h.

[0027] In the present invention, the diol suspension chain formed by the aminolysis of tung oil can be self-crosslinked under certain temperature conditions. The tung oil diol is introduced into the soft segment. The high temperature can make the conjugated double bonds of the side chain self-crosslinked to contribute covalent crosslinking sites, and 3-aminophenylboronic acid can react with isocyanate to participate in the crosslinking reaction of the polymer to form a crosslinking network. The two crosslinking systems are combined to optimize the mechanical properties of the elastomer. Since 3-aminophenylboronic acid opens the ring and dehydrates and closes the ring when it encounters water, the elastomer can self-heal under the induction of water at room temperature. At room temperature, 100% self-healing can be achieved. The benzene ring provides steric hindrance of the hard segment, so that the soft and hard segments interact with each other, and the excellent mechanical properties and fracture strain of the elastomer are balanced. Due to the long chain characteristics of the tung oil monomer, the waterborne polyurethane film has good reprocessability.

[0028] The advantages of the present invention are:

[0029] (1) A waterborne polyurethane material with high density of cross-linking sites was synthesized using polytetramethylene ether glycol and tung oil glycol as soft segments, isophorone diisocyanate as hard segment, dimethylol propionic acid as hydrophilic chain extender, 3-aminophenylboronic acid as end capping, and then triethylamine as neutralization. The material has good mechanical properties and fracture toughness. The tensile strength of the polyurethane film can reach 6.94 MPa, the elongation at break can reach 790.1%, and the film has good resilience.

[0030] (2) The self-crosslinking units (conjugated double bonds) contained in tung oil in natural woody oils are combined with water-based polyurethane and capped with 3-aminophenylboronic acid to design and synthesize a bio-based water-based polyurethane that combines toughness and self-healing properties.

[0031] (3) The waterborne polyurethane of the present invention has excellent room temperature water-induced self-healing properties and excellent reprocessability.

[0032] (4) At a high cross-linking density, the soft and hard segments interact with each other to form mobile segments. The polymer cross-linking network can be opened at a certain temperature, thus giving the plant oil-based room temperature water-induced self-healing elastomer the unique advantage of reproducible processing. After repeated recycling, its chemical structure does not change and its mechanical properties are stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the hydrogen NMR spectrum of the plant oil-based diol in Example 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the preparation route of the plant oil-based room temperature water-induced self-healing polyurethane elastomer in Example 2 of the present invention;

[0035] Figure 3 This is the infrared spectrum of the plant oil-based room temperature water-induced self-healing polyurethane elastomer in Example 2 of the present invention;

[0036] Figure 4 The mechanical pictures of the plant oil-based room temperature water-induced self-healing polyurethane elastomer in Examples 2-4 of the present invention;

[0037] Figure 5 This is a self-healing micrograph of the plant oil-based room temperature water-induced self-healing polyurethane elastomer prepared in Example 3 of the present invention;

[0038] Figure 6 This is a healing mechanics picture of the plant oil-based room temperature water-induced self-healing polyurethane elastomer prepared in Example 3 of the present invention;

[0039] Figure 7 This is a reprocessable photo of the plant oil-based room temperature water-induced self-healing polyurethane elastomer prepared in Example 3 of the present invention;

[0040] Figure 8 The mechanical properties of the room temperature water-induced self-healing polyurethane elastomer prepared in Example 3 of the present invention after three recycling;

[0041] Fig. 9 The mechanical properties of the room temperature water-induced self-healing polyurethane elastomer prepared in Examples 2, 3, and 4 of the present invention after healing for 24 hours;

[0042] Fig.10 This is a diagram of the mechanical properties of the room temperature water-induced self-healing polyurethane elastomer prepared in Examples 2, 3, and 4 of the present invention after being recycled three times. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0045] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0046] Example 1

[0047] Preparation of plant oil-based diol tung oil diol: According to molar parts, 100 parts of tung oil are placed in a single-necked flask, placed in an oil bath at 95°C to remove water, nitrogen is introduced into the single-necked flask, and then the temperature is lowered to 60°C. A rotor is placed in the single-necked flask for continuous stirring, 300 parts of diethanolamine and 3 parts of sodium methoxide are added, and the temperature is lowered to room temperature after 7 hours of reaction. The liquid is transferred to a beaker and 350 mL of dichloromethane (DCM) is added for dilution. Then it is washed with saturated sodium chloride solution 5 times until the solution is clear. Then anhydrous magnesium sulfate is added, the solution is dehydrated for 10 hours, and then placed in a vacuum rotary evaporator to remove dichloromethane (DCM) to obtain a viscous yellow tung oil monomer, i.e., tung oil diol, whose structural formula is

[0048] Figure 1 The H NMR spectrum of the conversion process of tung oil (TO) to tung oil diol (TOD) is shown. Compared with TO, the proton peaks of TOD at δ5.20 (-CH-), δ4.12 and δ4.29 (-CH2-) completely disappeared, and new peaks appeared at δ3.51 and δ3.72, which correspond to the methylene groups on both sides of the N atom. The complete disappearance of the (-CH-) proton peak in triglyceride means that it fully participates in the reaction, and the appearance of the new peak confirms the successful preparation of TOD.

[0049] Example 2

[0050] A plant oil-based room temperature water-induced self-healing polyurethane elastomer is synthesized, and the schematic diagram of the route is as follows Figure 2 As shown, the specific steps include:

[0051] According to mole ratio, 9.5 parts of polytetramethylene ether glycol (number average molecular weight of 2000g / mol) were poured into a three-necked flask and placed in an oven for 12 hours to remove water. Then 9.5 parts of tung oil glycol prepared in Example 1 were put into a three-necked flask, kept at a constant temperature of 75°C, mechanically stirred under a nitrogen atmosphere, 32 parts of isophorone diisocyanate were weighed and added dropwise to the reaction at constant pressure, 0.005 parts of dibutyltin dilaurate were added as catalyst, and the reaction was carried out at 75°C for 3 hours. After the diol reaction was completed, 10 parts of dimethylol propionic acid were added dropwise to the reaction as a hydrophilic chain extender at constant pressure, 0.005 parts of dibutyltin dilaurate were added as catalyst, and the reaction was carried out at 75°C for 3 hours. After the reaction of dimethylolpropionic acid is completed, 2 parts of 3-aminophenylboronic acid are dissolved in tetrahydrofuran solvent with five times the weight of 3-aminophenylboronic acid, and then dripped into the reaction at constant pressure, 0.005 parts of dibutyltin dilaurate are added as a catalyst, and the reaction is carried out at 75°C for 3 hours. After the reaction is completely completed, 10 parts of triethylamine are added, and the solution is neutralized by stirring at 30°C for 30 minutes. After cooling, 180 parts of deionized water are added into the three-necked flask, and then the speed is turned to 2000 rpm to vigorously stir the emulsion. After emulsification at 30°C for one hour, the emulsion obtained is rotary evaporated to remove tetrahydrofuran to obtain an aqueous polyurethane solution, and the plant oil-based room temperature water-induced self-healing polyurethane elastomer (BWPU) is obtained after natural air drying to evaporate the water.

[0052] During the entire reaction process, each time the next step of feeding is carried out, it is necessary to ensure that the previous step can react completely. Therefore, Fourier transform infrared spectroscopy is required (see Figure 3 ), ensuring that the hydroxyl groups in the diol can react completely during the reaction, and at the end of the reaction, ensuring that the isocyanate group and the hydroxyl group can react completely, and multiple characteristic peaks in the carbamate are obvious. Among them, the step of adding isophorone diisocyanate is prepolymerization, the step of adding dimethylol propionic acid is chain extension, and the step of adding 3-aminophenylboronic acid is end-capping. Figure 3 It can be seen that the NCO peak at 2260 gradually disappears as the reaction proceeds. The NH peak at 3295 appears. This indicates that the reaction is progressing and completed. The ultimate stress of the elastomer obtained after the water is evaporated is 6.94MPa through tensile testing. Figure 4 shown.

[0053] Example 3

[0054] A plant oil-based room temperature water-induced self-healing polyurethane elastomer is synthesized, which is different from Example 2 only in that 8.5 parts of polytetramethylene ether glycol, 8.5 parts of tung oil glycol, and 6 parts of 3-aminophenylboronic acid are used, and the remaining steps are the same as Example 2.

[0055] The ultimate stress of the obtained elastomer is 5.07MPa through tensile test. Figure 4 shown.

[0056] Example 4

[0057] A plant oil-based room temperature water-induced self-healing polyurethane elastomer is synthesized, which is different from Example 2 only in that: 7.5 parts of polytetramethylene ether glycol, 7.5 parts of tung oil glycol, and 10 parts of 3-aminophenylboronic acid are used, and the remaining steps are the same as Example 2.

[0058] The ultimate stress of the obtained elastomer is 3.31MPa through tensile test. Figure 4 shown.

[0059] The Fourier transform infrared spectra during the reaction of Example 3 and Example 4 are similar to those of Example 2, that is, the NCO peak at 2260 gradually disappears as the reaction proceeds, while the NH peak at 3295 appears, which indicates that the reaction proceeds and is completed.

[0060] Data Analysis:

[0061] The elastomer samples obtained in Examples 2-4 were hot pressed into uniform sheets with a thickness of 0.2 mm. Then they were cut into dumbbell-shaped sheets with a width of 2.05 mm and a thickness of 0.2 mm using a standard cutter. They were stretched at room temperature at a speed of 50 mm / min. A UTM2502 universal testing machine (Shenzhen Sansi Zongheng Technology Co., Ltd.) equipped with a 100N sensor was used. The specific data are shown in Table 1 below. It can be seen from Table 1 that the fracture strain and stress of the elastomer in Example 3 are optimal.

[0062] Table 1. Mechanical properties of plant oil-based room temperature water-induced self-healing elastomers

[0063] sample Stress(MPa) strain(%) Toughness(KJ / mol) Example 2 6.94 790.1 27.2 Example 3 5.07 1240.8 39.4 Example 4 3.31 673.8 18.5

[0064] It can be seen from Table 1 that a series of polyurethane elastomers with different mechanical properties can be obtained by adjusting the difference in the content of tung oil diol, polytetramethylene ether diol and 3-aminophenylboronic acid. Tung oil diol introduces the soft segment, and high temperature can cause the conjugated double bonds of its side chain to self-crosslink to contribute covalent crosslinking sites, while the benzene ring in 3-aminophenylboronic acid provides steric hindrance for the hard segment, allowing the soft and hard segments to interact with each other, balancing the excellent mechanical properties and fracture strain of the elastomer.

[0065] The elastic films of Examples 2-4 with a sample thickness of 0.5 mm were cut into standard dumbbell shapes. Each group had at least 3 pieces, which were cut with scissors and then tightly pressed against the wound. A drop of deionized water was dripped onto the wound. After being placed at room temperature for different periods of time, the self-healing conditions of the samples of Example 3 were as follows: Figure 5 As shown in the microphotograph, the mechanical test was carried out using an electronic universal testing machine. The test results are shown in Figure 6 and 9 As shown by Figure 5 ,6 As shown in Figure 9, the wound healed almost completely after 24 hours, and the mechanical properties were almost completely restored. 3-Aminophenylboronic acid can participate in the cross-linking reaction of the polymer to form a cross-linked network. It can also achieve self-healing by opening and closing the ring under water induction. At room temperature, it can achieve super strong self-healing performance.

[0066] Any of the plant oil-based room temperature water-induced self-healing elastomers in the above embodiments fully utilizes the characteristic that the conjugated double bonds on the pendant chains spontaneously cross-link during the reaction process to construct a stable covalent bridging network. The polymer cross-linking network can be opened at a certain temperature, thereby giving the plant oil-based room temperature water-induced self-healing elastomer a unique advantage of being reprocessable. After repeated recycling, there is no change in its chemical structure and the mechanical properties are stable. Figure 7 , Figure 8 and Fig.10 As shown, the specific test method is to heat-press the film into a film again at 150°C after the mechanical properties of the film are tested, and then cut it into a dumbbell shape for testing, and repeat the above steps.

[0067] The present invention introduces tung oil diol into the soft segment to make it self-crosslinked under certain temperature conditions, and uses 3-aminophenylboronic acid to react with isocyanate to construct a crosslinking network. The two crosslinking systems are combined to optimize the mechanical properties of the elastomer. Since 3-aminophenylboronic acid opens and dehydrates when it encounters water, the elastomer can self-heal under the induction of water at room temperature. Due to the long-chain characteristics of the tung oil monomer, the water-based polyurethane film has good reprocessability.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A plant oil-based room temperature water-induced self-healing polyurethane elastomer, characterized in that: The invention is prepared with polytetramethylene ether glycol and tung oil glycol as soft segments, isophorone diisocyanate as hard segments, dimethylol propionic acid as a hydrophilic chain extender, and 3-aminophenylboronic acid as a capping agent. Wherein, the structural formula of the tung oil glycol is 2. The plant oil-based room temperature water-induced self-healing polyurethane elastomer according to claim 1, characterized in that: The number average molecular weight of the polytetramethylene ether glycol is 2000 g / mol.

3. The plant oil-based room temperature water-induced self-healing polyurethane elastomer according to claim 1, characterized in that: The molar ratio of the polytetramethylene ether glycol to tung oil glycol is 1:

1.

4. The plant oil-based room temperature water-induced self-healing polyurethane elastomer according to claim 1, characterized in that: The molar ratio of the soft segment to the hard segment is 15-19:

32.

5. The plant oil-based room temperature water-induced self-healing polyurethane elastomer according to claim 1, characterized in that: The molar ratio of isophorone diisocyanate to dimethylol propionic acid is 32:

10.

6. The plant oil-based room temperature water-induced self-healing polyurethane elastomer according to claim 1, characterized in that: The ratio of the total mole number of the polytetramethylene ether glycol and the tung oil glycol to the mole number of 3-aminophenylboronic acid is 15-19:2-10.

7. The plant oil-based room temperature water-induced self-healing polyurethane elastomer according to any one of claims 1 to 6, characterized in that: In the preparation process, dibutyltin dilaurate is used as a catalyst.

8. A method for preparing a plant oil-based room temperature water-induced self-healing polyurethane elastomer according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: mixing polytetramethylene ether glycol and tung oil glycol, stirring at a constant temperature under a nitrogen atmosphere, adding isophorone diisocyanate and dibutyltin dilaurate to react, adding dimethylolpropionic acid and dibutyltin dilaurate to react, adding 3-aminophenylboric acid solution after the reaction of dimethylolpropionic acid is completed, adding dibutyltin dilaurate to react, adding triethylamine neutralization solution after the reaction is completed, adding water to stir and emulsify, rotary evaporation to obtain an aqueous polyurethane solution, and removing water to obtain the plant oil-based room temperature water-induced self-healing polyurethane elastomer.

9. The method for preparing the plant oil-based room temperature water-induced self-healing polyurethane elastomer according to claim 8, characterized in that: The temperature of the constant temperature stirring is 75°C.

10. The method for preparing the plant oil-based room temperature water-induced self-healing polyurethane elastomer according to claim 8 or 9, characterized in that: The reaction temperature was 75°C and the reaction time was 3 hours.

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