A recyclable and self-healing polyurethane silicone resin with excellent photocuring and photoreponse properties and its preparation method

Abstract

The present invention discloses a recyclable self-healing polyurethane silicone resin with excellent photocuring and light-responsive properties and a preparation method thereof, belonging to the technical field of light-responsive materials. The polyurethane silicone resin of the present invention comprises the following raw materials: polymerization monomers (propyl alcohol-substituted azobenzene monomer and hydroxyethyl acrylate), diisocyanate, bis-hydroxypropyl-terminated silicone oil, bis(2-hydroxyethyl) disulfide, triethanolamine, a catalyst and an inhibitor. The material prepared by the present invention contains a reversible light-responsive azobenzene structure, a dynamic reversible bond disulfide bond and an acrylate structure, endowing the material with excellent light responsiveness, self-healing performance and recyclability. In addition, the material prepared by the present invention also has a siloxane bond structure, and through the rearrangement reaction of the silicon-oxygen bond under high temperature and alkali-catalyzed conditions, the complete upgrade recycling of the material is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of light-responsive materials, and more specifically relates to a recyclable and self-healing polyurethane silicone resin with excellent photocuring and light-responsive properties and a preparation method thereof. Background Art

[0002] Polyurethane silicone resin has a large number of silicon-oxygen bonds in its structure, which endows it with advantages such as heat resistance, cold resistance, electrical insulation, and stable chemical resistance, and is widely used in many fields. However, during long-term use, the material will inevitably be damaged, which makes it unable to effectively perform its functions and even causes huge economic losses. Self-healing materials can repair the damage suffered by the material during use, and while ensuring the use performance of the material, can effectively extend its service life.

[0003] Self-healing materials can be classified into external aid type self-healing materials and intrinsic type self-healing materials according to their repair mechanisms. External aid type self-healing materials embed microcapsules or microvascular networks inside or on the surface of the material. When the material is damaged, the repair agent in the microcapsules or microvasculars is released and reacts with the catalyst to achieve the repair of the material. The number of repair times of external aid type self-healing materials is usually limited, which will have a certain impact on the service life of the material. Intrinsic type self-healing materials rely on their own chemical structure or physical properties to achieve self-healing. Such materials usually contain reversible chemical bonds (such as dynamic covalent bonds, hydrogen bonds, metal coordination bonds, etc.). When the material is damaged, these reversible bonds can be re-formed to achieve self-healing. The number of repair times of intrinsic type self-healing materials is more than that of external aid type self-healing materials.

[0004] At present, the research on self-healing mainly focuses on thermally responsive self-healing. However, the repair range of thermally responsive self-healing is limited, and at the same time, a relatively high temperature may damage the structure of the material itself. In addition, the cost of polyurethane silicone materials is high and it is difficult to degrade, which does not conform to the concept of green development and sustainable development. Therefore, it is urgent to recycle and utilize polyurethane silicone materials. And the polyurethane silicone materials obtained by conventional material recycling methods are difficult to reach the use performance of the raw materials, reducing the use value of the recycled materials. Therefore, it is of great significance to develop a recyclable and self-healing polyurethane silicone resin while ensuring excellent photocuring and light-responsive properties. Summary of the Invention

[0005] The purpose of the present invention is to provide a recyclable and self-healing polyurethane silicone resin with excellent photocuring and light-responsive properties and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art, and ensure that the performance of the self-healing polyurethane silicone resin after recycling and reuse is equivalent to or even higher than the initial performance.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention: Provide a recyclable and self-healing polyurethane silicone resin, which comprises the following raw materials for preparation in molar parts:

[0008] 3 to 10 mmol parts of polymerization monomer, 0.02 to 0.05 mol parts of diisocyanate, 0.01 to 0.03 mol parts of bis(2-hydroxyethyl) silicone oil, 0.01 to 0.03 mol parts of bis(2-hydroxyethyl) disulfide, and 1 to 5 mmol parts of triethanolamine;

[0009] The polymerization monomer includes propanol-substituted azobenzene monomer and hydroxyethyl acrylate, and the mass ratio of the propanol-substituted azobenzene monomer to hydroxyethyl acrylate is 2.2:1 to 1:1.06;

[0010] The raw materials for preparing the recyclable and self-healing polyurethane silicone resin further include a catalyst and an inhibitor; the dosage of the catalyst is preferably 0.2 to 0.6% of the total mass of the polymerization monomer, diisocyanate, bis(2-hydroxyethyl) silicone oil, bis(2-hydroxyethyl) disulfide, and triethanolamine, and more preferably 0.4 to 0.5% of the total mass of the polymerization monomer, diisocyanate, bis(2-hydroxyethyl) silicone oil, bis(2-hydroxyethyl) disulfide, and triethanolamine; the dosage of the inhibitor is preferably 0.1 to 0.5% of the total mass of the polymerization monomer, diisocyanate, bis(2-hydroxyethyl) silicone oil, bis(2-hydroxyethyl) disulfide, and triethanolamine, and more preferably 0.3 to 0.4% of the total mass of the polymerization monomer, diisocyanate, bis(2-hydroxyethyl) silicone oil, bis(2-hydroxyethyl) disulfide, and triethanolamine.

[0011] Through the specific selection of raw materials, the present invention ensures that the prepared polyurethane organosilicon resin has excellent photocuring and light-responsive properties, and also ensures that the properties of the self-healing polyurethane organosilicon resin after recycling are equivalent to or even higher than those at the initial stage. Among them, the diisocyanate reacts with other raw materials containing hydroxyl groups to form urethane groups, which act together with other hard and soft segments in the material, thereby ensuring that the synthesized polyurethane material has excellent wear resistance, high elasticity, and good designability. Both hydroxyethyl acrylate and propanol-substituted azobenzene monomer are compounds with hydroxyl groups at the ends, and the double bonds therein can quickly participate in free radical polymerization reactions to form polymers, making the reaction more complete. The combined use of hydroxyethyl acrylate and propanol-substituted azobenzene monomer can obtain curability. Bis(2-hydroxyethyl) disulfide makes the resin structure contain disulfide bonds, and the disulfide bond structure can ensure that the resin has more excellent self-healing and recyclable properties. Triethanolamine is a tri-terminal hydroxyl monomer, which can react with the molecular chain of linear polyurethane organosilicon resin to form a symmetric branched structure, and has a lower viscosity compared with linear polyurethane organosilicon resin materials of the same molecular weight, which is more convenient for the subsequent processing of the material. The silicon-oxygen main chain structure of bis-hydroxypropyl-terminated silicone oil provides the siloxane bond structure in the material. Through the rearrangement reaction of siloxane bonds under high temperature and alkali-catalyzed conditions, the complete upgrade and recycling of the material can be achieved, and the performance of the polyurethane organosilicon resin after recycling treatment is higher than that at the initial stage.

[0012] By controlling the amounts of the catalyst and inhibitor, the present invention can ensure sufficient reaction, improve production efficiency, and avoid gelation in the system. Excessive catalyst amount will cause gelation in the system, while too low amount will result in long reaction time and reduced production efficiency. Too low inhibitor amount will lead to poor inhibition effect and gelation in the system, and too high amount will slow down the photocuring reaction of the resin or cause incomplete curing.

[0013] Preferably, the preparation of the propanol-substituted azobenzene monomer includes the following steps:

[0014] 4-Hydroxyazobenzene, potassium carbonate, bromopropanol, and a solvent are mixed and heated for reaction to obtain the propanol-substituted azobenzene monomer;

[0015] The molar ratio of 4-hydroxyazobenzene, potassium carbonate, and bromopropanol is 0.5-1:1-1.5:0.5-1; the temperature of the heating reaction is 65-75 °C.

[0016] The present invention does not specifically limit the type and amount of the solvent used in the preparation process of the propanol-substituted azobenzene monomer, as long as it can dissolve the reaction raw materials and the reaction can proceed smoothly.

[0017] The synthesis reaction formula of the propanol-substituted azobenzene monomer of the present invention is as follows:

[0018]

[0019] Preferably, the diisocyanate includes isophorone diisocyanate or trimethylhexamethylene diisocyanate; the molecular weight of the bis - hydroxypropyl - terminated silicone oil is 1000 - 2000 g / mol; the catalyst includes dibutyltin dilaurate and / or bismuth neodecanoate; the inhibitor includes 4 - methoxyphenol and / or hydroquinone.

[0020] The second technical solution of the present invention: Provide the preparation method of the recyclable and reusable self - healing polyurethane silicone resin as described above, including the following steps:

[0021] Mix the bis - hydroxypropyl - terminated silicone oil, bis(2 - hydroxyethyl) disulfide, diisocyanate, catalyst and organic solvent, and then carry out a prepolymerization reaction to obtain a polyurethane silicone prepolymer;

[0022] Mix the polyurethane silicone prepolymer, polymerization monomer, base catalyst, inhibitor and organic solvent, and then carry out a first reaction to obtain an intermediate product;

[0023] Mix the intermediate product, triethanolamine and organic solvent, and then carry out a second reaction to obtain the recyclable and reusable self - healing polyurethane silicone resin.

[0024] The synthesis reaction formula of the recyclable and reusable self - healing polyurethane silicone resin of the present invention is as follows:

[0025]

[0026] Among them, the structural formula of R1 is: The structural formula of R2 is: The structural formula of R3 is independently: When the dosage ratio of propanol - substituted azobenzene monomer and hydroxyethyl acrylate is different, the substitution amounts of azobenzene group and ethyl acrylate group in the recyclable and reusable self - healing polyurethane silicone resin are also different; the structural formula of R4 is:

[0027]

[0028] Preferably, the organic solvent independently includes acetone and / or N,N - dimethylformamide; the base catalyst includes tetramethylammonium hydroxide.

[0029] Preferably, the dosage of the base catalyst is 0.2 - 1‰ of the total mass of the polymerization monomer, diisocyanate, bis - hydroxypropyl - terminated silicone oil, bis(2 - hydroxyethyl) disulfide and triethanolamine.

[0030] Preferably, the temperature of the prepolymerization reaction is 55-65°C, and the time of the prepolymerization reaction is 5-6 h; the temperatures of the first reaction and the second reaction are independently 50-70°C, and the times of the first reaction and the second reaction are independently 3-5 h.

[0031] Technical solution three of the present invention: Provide a recycling method for the recyclable self-healing polyurethane silicone resin described above, including the following steps:

[0032] Mix the recyclable self-healing polyurethane silicone resin to be recycled, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide and a solvent, and then carry out a heating reaction to obtain a vinyl-terminated polyurethane silicone recycled resin;

[0033] Mix the vinyl-terminated polyurethane silicone recycled resin, hydrogen-containing silicone oil and ethanol-modified chloroplatinic acid catalyst, and then carry out curing to obtain a reusable polyurethane silicone material.

[0034] Preferably, the mass ratio of the recyclable self-healing polyurethane silicone resin to be recycled, tetramethyldivinyldisiloxane and tetramethylammonium hydroxide is 5:0.02:0.01-5:0.06:0.01; the vinyl content in the vinyl-terminated polyurethane silicone recycled resin is 0.1-0.3 wt%.

[0035] Preferably, the mass ratio of the vinyl-terminated polyurethane silicone recycled resin, hydrogen-containing silicone oil and ethanol-modified chloroplatinic acid catalyst is 5.05:0.075:0.016-5.05:0.187:0.016; the silicon-hydrogen content in the hydrogen-containing silicone oil is 0.2-0.5 wt%.

[0036] Preferably, the temperature of the heating reaction is 80-110°C, and the time of the heating reaction is 5-7 h; the temperature of the curing is 130-160°C, and the time of the curing is 20-30 min.

[0037] The present invention does not specifically limit the type and amount of the solvent used in the recycling method of the recyclable self-healing polyurethane silicone resin, as long as it can dissolve the reaction raw materials and the reaction can proceed smoothly.

[0038] The present invention discloses the following technical effects:

[0039] 1. The recyclable self-healing polyurethane silicone resin of the present invention has a symmetric branched structure, and has a lower viscosity compared with a linear polyurethane silicone resin material of the same molecular weight, which is more convenient for the subsequent processing of the material.

[0040] 2. The recyclable and self-healing polyurethane silicone resin of the present invention is prepared from a polymerization monomer with a hydroxyl group at the end and a disulfide compound, enabling the polyurethane silicone resin to have the ability of photo-responsive self-healing and to achieve self-healing within a short time.

[0041] 3. The recyclable and self-healing polyurethane silicone resin of the present invention contains a reversible photo-responsive azobenzene structure, a dynamic reversible bond disulfide bond, and an acrylate structure, endowing the material with excellent photo-responsiveness, self-healing performance, and recyclability. In addition, the recyclable and self-healing polyurethane silicone resin of the present invention also has a siloxane bond structure, and through the rearrangement reaction of the silicon-oxygen bond under high temperature and base-catalyzed conditions, the complete upgrade cycle recycling of the material is realized.

[0042] 4. The recyclable and self-healing polyurethane silicone resin of the present invention can achieve the upgrade cycle recycling of the resin, and the performance of the material after upgrade recycling is better than that before recycling. Description of the Drawings

[0043] Figure 1 It is the nuclear magnetic spectrum of the propanol-substituted azobenzene monomer obtained in Example 1;

[0044] Figure 2 It is the infrared spectrum of the propanol-substituted azobenzene, isophorone diisocyanate, and the obtained product described in Example 2;

[0045] Figure 3 It is the stress-strain curve of the cured splines prepared from the polyurethane silicone resins obtained in Examples 2-5 and Comparative Example 1;

[0046] Figure 4 It is the self-healing performance test result diagram of the polyurethane silicone resins obtained in Examples 2-5 and Comparative Examples 1-2;

[0047] Figure 5 It is the physical diagram of the cured polyurethane silicone resin to be recycled described in Examples 6-10 and the physical diagram of the vinyl-terminated polyurethane silicone recycled resin obtained after upgrade cycle recycling dissolved in toluene;

[0048] Figure 6 It is the stress-strain curve of the upgraded recycled polyurethane silicone materials obtained in Examples 6-10 and the silicone material obtained in Comparative Example 3. Detailed Embodiments

[0049] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0050] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0051] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0052] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0053] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0054] Unless otherwise specified, the raw materials used in the following examples, comparative examples and effect verification examples are all commercially available products.

[0055] Example 1

[0056] The preparation of propanol substituted azobenzene comprises the following steps:

[0057] 4-Hydroxyazobenzene (17.6 g, 0.0936 mol), potassium carbonate (18.48 g, 0.1339 mol), bromopropanol (13.62 g, 0.0980 mol) and acetone (150 mL) were added into a three-necked flask, and the mixture was heated in an oil bath at 70°C for 12 h. The liquid mixture after the reaction was filtered while hot to remove potassium carbonate, and the filtrate was subjected to rotary evaporation to obtain a crude azo product, which was dissolved in a solution of methanol and water in a volume ratio of 2:1 and recrystallized to obtain yellow propanol substituted azobenzene.

[0058] The structure of the obtained propanol-substituted azobenzene was characterized using a Bruker UAVANCEⅢ 400 MHz nuclear magnetic resonance spectrometer.

[0059] The characterization method is as follows: The obtained propanol-substituted azobenzene is dissolved in deuterated chloroform reagent (CDCl3), and tetramethylsilane (TMS) is used as an internal standard. The results are as Figure 1 shown.

[0060] Figure 1 The NMR spectrum of the propanol-substituted azobenzene monomer obtained in Example 1. Figure 1 In Figure 1 , the proton peaks at 7.38 ppm, 6.76 ppm, and 7.82 ppm are the proton peaks on the benzene ring ( Figure 1 at positions a, b, and c in Figure 1 ), the proton peak at 7.45 ppm is the proton peak at the ortho position of the benzene ring adjacent to the ether bond ( Figure 1 at position d in Figure 1 ), the proton peak at 3.91 ppm is the proton peak on -CH2- adjacent to the ether bond ( Figure 1 at position e in Figure 1 ), the proton peak at 1.23 ppm is the proton peak on -CH2- ( Figure 1 at position f in Figure 1 ), and the proton peak at 3.67 ppm is the proton peak on -CH2- adjacent to the hydroxyl group ( Figure 1 at position g in Figure 1 ). Judging from the characteristic peaks, its structure is the same as the theoretically obtained product structure, indicating that propanol-substituted azobenzene has been successfully synthesized.

[0061] Example 2

[0062] This example provides the preparation of a polyurethane organosilicon resin, and the specific steps are as follows:

[0063] 20 g (0.01 mol) of bis-hydroxypropyl silicone oil and 1.543 g (0.01 mol) of bis(2-hydroxyethyl) disulfide are added to a four-necked flask equipped with a mechanical stirring device and a condensing reflux device and mixed evenly. A mixture of 6.66 g (0.03 mol) of isophorone diisocyanate, dibutyltin dilaurate (the dosage is 0.3% of the total mass of other raw materials except 4-methoxyphenol), and 10 mL of acetone is slowly added dropwise at 60 °C. The reaction is carried out at 60 °C for 5 h to obtain a polyurethane organosilicon prepolymer; then, a mixture of 0.58 g (5 mmol) of 2-hydroxyethyl acrylate, 1.28 g (5 mmol) of the propanol-substituted azobenzene prepared in Example 1, pentahydrate of tetramethylammonium hydroxide (the dosage is 1‰ of the total mass of other raw materials except dibutyltin dilaurate and 4-methoxyphenol), 4-methoxyphenol (the dosage is 0.3% of the total mass of other raw materials except dibutyltin dilaurate), and 5 mL of acetone is added dropwise. The reaction is carried out at 65 °C for 4 h, and finally, a mixture of 0.492 g (3.3 mmol) of triethanolamine and 5 mL of acetone is added dropwise. The reaction is carried out at 65 °C for 3 h to obtain a polyurethane organosilicon resin.

[0064] The structure of the polyurethane organosilicon resin prepared in this example is characterized by a German bruker Vertex70 infrared spectrometer, and the sample is prepared by the potassium bromide tablet pressing method. The test scanning range is 4000 - 400 cm -1, with a resolution of 4 cm -1 , and the results are as Figure 2 shown.

[0065] Figure 2 It is the infrared spectrogram of propanol-substituted azobenzene, isophorone diisocyanate and the obtained product described in Example 2. Figure 2 In it, 3286 cm -1 is the characteristic absorption peak of -OH, and 2260 cm -1 is the characteristic absorption peak of -NCO. According to the characteristic peaks, it is judged that the characteristic peaks of hydroxyl and isocyanate groups in the product disappear, proving that the polyurethane silicone resin is successfully prepared.

[0066] Example 3

[0067] This example provides the preparation of polyurethane silicone resin, and the specific steps are as follows:

[0068] Add 20 g (0.01 mol) of bis-hydroxypropyl silicone oil and 1.543 g (0.01 mol) of bis(2-hydroxyethyl) disulfide into a four-necked flask equipped with a mechanical stirring device and a condensation reflux device, mix evenly, and slowly add a mixture of 6.308 g (0.03 mol) of trimethylhexamethylene diisocyanate, dibutyltin dilaurate (the dosage is 0.3% of the total mass of other raw materials except 4-methoxyphenol) and 10 mL of acetone dropwise at 60 °C, keep the temperature at 60 °C and react for 5 h to obtain a polyurethane silicone prepolymer; then add dropwise a mixture of 0.58 g (5 mmol) of hydroxyethyl acrylate, 1.28 g (5 mmol) of propanol-substituted azobenzene prepared in Example 1, tetramethylammonium hydroxide pentahydrate (the dosage is 1‰ of the total mass of other raw materials except dibutyltin dilaurate and 4-methoxyphenol), 4-methoxyphenol (the dosage is 0.3% of the total mass of other raw materials except dibutyltin dilaurate) and 5 mL of acetone, react at 65 °C for 4 h, and finally add dropwise a mixture of 0.492 g (3.3 mmol) of triethanolamine and 5 ml of acetone, react at 65 °C for 3 h to obtain a polyurethane silicone resin.

[0069] Example 4

[0070] This example provides the preparation of polyurethane silicone resin, and the specific steps are as follows:

[0071] 20 g (0.01 mol) of bis - hydroxypropyl silicone oil and 1.543 g (0.01 mol) of bis(2 - hydroxyethyl) disulfide were added to a four - necked flask equipped with a mechanical stirring device and a condensation reflux device and mixed evenly. A mixture of 6.66 g (0.03 mol) of isophorone diisocyanate, dibutyltin dilaurate (the dosage is 0.3% of the total mass of other raw materials except 4 - methoxyphenol), and 10 mL of acetone was slowly added dropwise at 60 °C. The reaction was carried out with heat preservation at 60 °C for 5 h to obtain a polyurethane - silicone prepolymer; then a mixture of 0.696 g (6 mmol) of 2 - hydroxyethyl acrylate, 1.024 g (4 mmol) of the propanol - substituted azobenzene prepared in Example 1, pentahydrate of tetramethylammonium hydroxide (the dosage is 1‰ of the total mass of other raw materials except dibutyltin dilaurate and 4 - methoxyphenol), 4 - methoxyphenol (the dosage is 0.3% of the total mass of other raw materials except dibutyltin dilaurate), and 5 mL of acetone was added dropwise, and the reaction was carried out at 65 °C for 4 h. Finally, a mixture of 0.492 g (3.3 mmol) of triethanolamine and 5 ml of acetone was added dropwise, and the reaction was carried out at 65 °C for 3 h to obtain a polyurethane - silicone resin.

[0072] Example 5

[0073] This example provides the preparation of a polyurethane - silicone resin, and the specific steps are as follows:

[0074] 20 g (0.01 mol) of bis - hydroxypropyl silicone oil and 1.543 g (0.01 mol) of bis(2 - hydroxyethyl) disulfide were added to a four - necked flask equipped with a mechanical stirring device and a condensation reflux device and mixed evenly. A mixture of 6.66 g (0.03 mol) of isophorone diisocyanate, dibutyltin dilaurate (the dosage is 0.3% of the total mass of other raw materials except 4 - methoxyphenol), and 10 mL of acetone was slowly added dropwise at 60 °C. The reaction was carried out with heat preservation at 60 °C for 5 h to obtain a polyurethane - silicone prepolymer; then a mixture of 0.812 g (7 mmol) of 2 - hydroxyethyl acrylate, 0.768 g (3 mmol) of the propanol - substituted azobenzene prepared in Example 1, pentahydrate of tetramethylammonium hydroxide (the dosage is 1‰ of the total mass of other raw materials except dibutyltin dilaurate and 4 - methoxyphenol), 4 - methoxyphenol (the dosage is 0.3% of the total mass of other raw materials except dibutyltin dilaurate), and 5 mL of acetone was added dropwise, and the reaction was carried out at 65 °C for 4 h. Finally, a mixture of 0.492 g (3.3 mmol) of triethanolamine and 5 ml of acetone was added dropwise, and the reaction was carried out at 65 °C for 3 h to obtain a polyurethane - silicone resin.

[0075] Comparative Example 1

[0076] This comparative example provides the preparation of a polyurethane - silicone resin, and the specific steps are as follows:

[0077] The difference from Example 2 is that "0.58 g (5 mmol) of 2-hydroxyethyl acrylate and 1.28 g (5 mmol) of the propanol-substituted azobenzene prepared in Example 1" used is replaced with "1.16 g (10 mmol) of 2-hydroxyethyl acrylate", and the others are the same as in Example 2.

[0078] Comparative Example 2

[0079] This comparative example provides the preparation of a polyurethane organosilicon resin, and the specific steps are as follows:

[0080] The difference from Example 2 is that "0.58 g (5 mmol) of 2-hydroxyethyl acrylate and 1.28 g (5 mmol) of the propanol-substituted azobenzene prepared in Example 1" used is replaced with "12.56 g (10 mmol) of the propanol-substituted azobenzene prepared in Example 1", and the others are the same as in Example 2.

[0081] Effect Verification Example 1

[0082] The resins prepared in Examples 2 to 5 and Comparative Examples 1 to 2 were made into photo-responsive self-healing coatings and cured splines, and the preparation methods are as follows:

[0083] The resins prepared in Examples 2 to 5 and Comparative Examples 1 to 2 were respectively mixed with photoinitiator 1173 (photoinitiator 1173 accounted for 4% of the resin mass), and were rapidly stirred to disperse evenly for standby.

[0084] Preparation of photo-responsive self-healing coating: The above-mentioned uniformly dispersed mixture was placed on a glass slide and scraped evenly with a 250-μm film applicator, and then placed at room temperature to evaporate the solvent completely, and was photocured with an LED ultraviolet lamp (30 s) to obtain a photo-responsive self-healing coating.

[0085] Preparation of cured spline: The above-mentioned uniformly dispersed mixture was poured into a dumbbell-shaped mold, the solvent was evaporated completely, and was photocured with an LED ultraviolet lamp (radiation intensity of 800 mW / cm 2 ) (1 min) to obtain a cured spline.

[0086] The photo-responsive self-healing coatings and cured splines prepared in this effect verification example were subjected to performance tests, and the specific test methods are as follows:

[0087] 1. Stress-strain test:

[0088] The cured splines were tested with reference to the standard of GB / T 1040-2006, and the results are as Figure 3 shown.

[0089] 2. Self-healing performance test:

[0090] Use a scalpel to gently make a clearly visible scratch on the light-responsive self-healing coating. Place the sample under an LED ultraviolet lamp for irradiation (radiation intensity: 2100 mW / cm 2 ). After the light-responsive self-healing coating cools down, use the 5× objective lens of an MP41 polarizing microscope to observe and photograph the self-healing process of the light-responsive self-healing coating, so as to study the self-healing behavior of the polyurethane organosilicon resin with different azobenzene structure contents. The results are as Figure 4 shown.

[0091] Figure 3 Figure 220 shows the stress-strain curves of the cured splines prepared from the polyurethane organosilicon resins obtained in Examples 2 to 5 and Comparative Example 1. Figure 4 Figure 224 shows the test results of the self-healing performance of the polyurethane organosilicon resins obtained in Examples 2 to 5 and Comparative Examples 1 to 2. It can be seen from Figure 3 and Figure 4 that during the preparation of the polyurethane organosilicon resin, as the content of carbon-carbon double bonds gradually increases, the tensile strength of the cured splines gradually increases. Among them, for the resin prepared in Comparative Example 2, the end groups are all azobenzene structures and there are no carbon-carbon double bonds in the molecular structure, and the resin cannot be cured and is in a viscous liquid state, making it difficult to conduct stress-strain performance tests. As the content of azobenzene structures in the resin increases, the repair time of the scratches on the coating gradually shortens. Among them, the resin in Comparative Example 1 does not contain azobenzene structures and has no light-responsive effect, so it is difficult for the coating to achieve self-healing in a short time.

[0092] Example 6

[0093] This example provides a method for recycling polyurethane organosilicon resin, and the specific steps are as follows:

[0094] Mix 5 g of the cured polyurethane organosilicon resin to be recycled in Example 2 with 0.035 g of tetramethyldivinyldisiloxane, 0.01 g of tetramethylammonium hydroxide pentahydrate (alkali catalyst), and 20 mL of toluene, react at 100 °C for 6 h, and then distill under reduced pressure for 2 h to remove toluene to obtain a recycled polyurethane organosilicon resin with vinyl groups at the ends, and its vinyl content is 0.2 wt%.

[0095] Take 5.05 g of the recycled polyurethane organosilicon resin with vinyl groups at the ends, 0.104 g of hydrogen-containing silicone oil (silicon-hydrogen content: 0.36 wt%), and 0.016 g of ethanol-modified chloroplatinic acid catalyst (purchased from Shanghai Neutron Star Chemical Technology Co., Ltd.), mix them evenly (dichloromethane can be added during this period to adjust to a workable viscosity), and cure at 150 °C for 30 min to obtain an upgraded recycled polyurethane organosilicon material.

[0096] Example 7

[0097] This embodiment provides a method for recycling polyurethane silicone resin, and the specific steps are as follows:

[0098] The difference from Example 6 is that "the cured polyurethane silicone resin to be recycled in Example 2" is replaced with "the cured polyurethane silicone resin to be recycled in Example 3", and the others are the same as in Example 6.

[0099] Example 8

[0100] This embodiment provides a method for recycling polyurethane silicone resin, and the specific steps are as follows:

[0101] The difference from Example 6 is that "the cured polyurethane silicone resin to be recycled in Example 2" is replaced with "the cured polyurethane silicone resin to be recycled in Example 4", and the others are the same as in Example 6.

[0102] Example 9

[0103] This embodiment provides a method for recycling polyurethane silicone resin, and the specific steps are as follows:

[0104] The difference from Example 6 is that "the cured polyurethane silicone resin to be recycled in Example 2" is replaced with "the cured polyurethane silicone resin to be recycled in Example 5", and the others are the same as in Example 6.

[0105] Example 10

[0106] This embodiment provides a method for recycling polyurethane silicone resin, and the specific steps are as follows:

[0107] The difference from Example 6 is that "the cured polyurethane silicone resin to be recycled in Example 2" is replaced with "the cured polyurethane silicone resin to be recycled in Comparative Example 1", and the others are the same as in Example 6.

[0108] Figure 5 It is the physical diagram of the cured polyurethane silicone resin to be recycled described in Examples 6 to 10 and the physical diagram of the vinyl-terminated polyurethane silicone recycled resin obtained by upgraded recycling and dissolved in toluene. From Figure 5 it can be seen that the solution of the vinyl-terminated polyurethane silicone recycled resin obtained by upgraded recycling and dissolved in toluene is in a homogeneous state, and the polyurethane silicone resin prepared by the present invention can achieve effective recycling.

[0109] Comparative Example 3

[0110] This comparative example provides the preparation of a conventional silicone resin with the same silicon hydride content as in Example 6, and the specific steps are as follows:

[0111] Conventionally, vinyl silicone oil with a vinyl content of 0.2 wt.% was mixed uniformly with 0.103 g of hydrogen-containing silicone oil (silicon-hydrogen content of 0.36 wt.%) and 0.015 g of ethanol-modified chloroplatinic acid catalyst, and cured at 150 °C for 30 min to obtain a conventional silicone resin as a comparative sample.

[0112] Effect Verification Example 2

[0113] The upgraded recycled polyurethane silicone materials obtained in Examples 6 - 10 and the silicone resin prepared in Comparative Example 3 were made into cured splines. The preparation method is as follows:

[0114] The upgraded recycled polyurethane silicone materials obtained in Examples 6 - 10 and the silicone resin prepared in Comparative Example 3 were respectively mixed with photoinitiator 1173 (photoinitiator 1173 accounted for 4% of the resin mass), and rapidly stirred to disperse evenly for standby. The above-mentioned uniformly dispersed mixture was poured into a dumbbell-shaped mold, and the solvent was completely volatilized. Then, it was subjected to photocuring (1 min) using an LED ultraviolet lamp (radiation intensity of 800 mW / cm 2 ) to obtain cured splines.

[0115] Performance tests were carried out on the cured splines prepared in this effect verification example. The specific test methods are as follows:

[0116] Stress-strain test:

[0117] The cured splines were tested with reference to the standard of GB / T 1040 - 2006, and the results are as Figure 6 shown.

[0118] Figure 6 are the stress-strain curves of the upgraded recycled polyurethane silicone materials obtained in Examples 6 - 10 and the silicone materials obtained in Comparative Example 3. From the Figure 6 and Figure 3 data comparison, it can be seen that the tensile strength of the upgraded recycled polyurethane silicone materials prepared in this invention is higher than that of the corresponding raw materials (the polyurethane silicone resins prepared in Examples 2 - 5), and is much greater than that of the conventional silicone materials with the same vinyl content. It shows that the polyurethane silicone resin of this invention can achieve the upgrade recycling of the resin, and the performance of the upgraded recycled material is better than that of the material before recycling.

[0119] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same and similar parts among the embodiments, reference can be made to each other.

[0120] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A recycling method for a recyclable and self - healing polyurethane silicone resin, characterized in that, It includes the following steps: Mix the cured recyclable self-healing polyurethane silicone resin to be recycled, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide pentahydrate and a solvent, and then carry out a heating reaction to obtain a vinyl-terminated polyurethane silicone recycled resin; Mix the vinyl-terminated polyurethane silicone recycled resin, hydrogen-containing silicone oil and ethanol-modified chloroplatinic acid catalyst, and then carry out curing to obtain a reusable polyurethane silicone material; The recyclable self-healing polyurethane silicone resin includes the following raw materials in molar parts: 3-10 mmol parts of polymerization monomers, 0.02-0.05 mol parts of diisocyanate, 0.01-0.03 mol parts of bis(2-hydroxyethyl) disulfide, 0.01-0.03 mol parts of bis(2-hydroxyethyl) disulfide and 1-5 mmol parts of triethanolamine; The polymerization monomers include propanol-substituted azobenzene monomers and 2-hydroxyethyl acrylate, and the mass ratio of the propanol-substituted azobenzene monomers to 2-hydroxyethyl acrylate is 2.2:1 to 1:1.06; the structural formula of the propanol-substituted azobenzene monomers is ; the preparation raw materials of the recyclable self-healing polyurethane silicone resin further include a catalyst and an inhibitor. The dosage of the catalyst is 0.2 to 0.6% of the total mass of the polymerization monomers, diisocyanate, double-end hydroxypropyl silicone oil, bis(2-hydroxyethyl) disulfide and triethanolamine, and the dosage of the inhibitor is 0.1 to 0.5% of the total mass of the polymerization monomers, diisocyanate, double-end hydroxypropyl silicone oil, bis(2-hydroxyethyl) disulfide and triethanolamine; The cured recyclable self-healing polyurethane silicone resin to be recycled is in the form of a coating or a cured spline; The curing steps are as follows: Mix the recyclable self-healing polyurethane silicone resin with photoinitiator 1173, where the photoinitiator 1173 accounts for 4% of the mass of the recyclable self-healing polyurethane silicone resin, and quickly stir to disperse it evenly for standby; Place the above-mentioned evenly dispersed mixture on a glass slide and scrape it evenly with a 250-μm film applicator to completely volatilize the solvent, and use an LED ultraviolet lamp for photocuring for 30 s to obtain a coating; or, Pour the above-mentioned evenly dispersed mixture into a dumbbell-shaped mold, completely volatilize the solvent, and use an LED ultraviolet lamp with a radiation intensity of 800 mW / cm 2 , and carry out photocuring for 1 min to obtain a cured sample bar.

2. The recycling method according to claim 1, characterized in that, The mass ratio of the recyclable self-healing polyurethane silicone resin, tetramethyldivinyldisiloxane and tetramethylammonium hydroxide pentahydrate to be recycled is 5:0.02:0.01 - 5:0.06:0.01; and / or, the vinyl content in the vinyl-terminated polyurethane silicone recycled resin is 0.1-0.3 wt%.

3. The recycling method according to claim 1, characterized in that, The mass ratio of the vinyl-terminated polyurethane silicone recycled resin, hydrogen-containing silicone oil and ethanol-modified chloroplatinic acid catalyst is 5.05:0.075:0.016 - 5.05:0.187:0.016; and / or, the silicon-hydrogen content in the hydrogen-containing silicone oil is 0.2-0.5 wt%.

4. The recycling method according to claim 1, characterized in that, The temperature of the heating reaction is 80-110 °C, and the time of the heating reaction is 5-7 h; and / or, the temperature for curing after mixing the vinyl-terminated polyurethane silicone recycled resin, hydrogen-containing silicone oil and ethanol-modified chloroplatinic acid catalyst is 130-160 °C, and the curing time is 20-30 min.

5. The recycling method according to claim 1, wherein The preparation of the propanol-substituted azobenzene monomer includes the following steps: Mix 4-hydroxyazobenzene, potassium carbonate, bromopropanol and a solvent, and then carry out a heating reaction to obtain the propanol-substituted azobenzene monomer; and / or, the molar ratio of 4-hydroxyazobenzene, potassium carbonate and bromopropanol is 0.5-1:1-1.5:0.5-1; and / or, the temperature of the heating reaction is 65-75 °C.

6. The recycling method according to claim 1, wherein The diisocyanate includes isophorone diisocyanate or trimethylhexamethylene diisocyanate; and / or, the molecular weight of the bis(2-hydroxypropyl) silicone oil is 1000-2000 g / mol; and / or, the catalyst includes dibutyltin dilaurate and / or bismuth neodecanoate; and / or, the inhibitor includes 4-methoxyphenol and / or hydroquinone.

7. The recycling method according to claim 1, wherein The preparation steps of the recyclable self-healing polyurethane silicone resin include: Mix bis(2-hydroxypropyl) silicone oil, bis(2-hydroxyethyl) disulfide, diisocyanate, a catalyst and an organic solvent, and then carry out a prepolymerization reaction to obtain a polyurethane silicone prepolymer; Mix the polyurethane silicone prepolymer, polymerization monomers, a base catalyst, an inhibitor and an organic solvent, and then carry out a first reaction to obtain an intermediate product; Mix the intermediate product, triethanolamine and organic solvent and then carry out the second reaction to obtain the recyclable self-healing polyurethane silicone resin.

8. The recycling method according to claim 7, wherein The organic solvent independently includes acetone and / or N,N-dimethylformamide; and / or, the base catalyst includes tetramethylammonium hydroxide pentahydrate; and / or, the dosage of the base catalyst is 0.2 to 1‰ of the total mass of the polymerization monomer, diisocyanate, bis(2-hydroxypropyl)silicone oil, bis(2-hydroxyethyl) disulfide and triethanolamine.

9. The recycling method according to claim 7, wherein The temperature of the prepolymerization reaction is 55 to 65 °C, and the time of the prepolymerization reaction is 5 to 6 h; and / or, the temperatures of the first reaction and the second reaction are independently 50 to 70 °C, and the times of the first reaction and the second reaction are independently 3 to 5 h.

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