A self-repairing TPU color-changing film and its preparation process

Abstract

The present invention discloses a self-repairing TPU color-changing film and a preparation process thereof, and relates to the technical field of color-changing films. The preparation process comprises the following steps: step 1: adding the raw materials of the TPU color-changing material into a mixer, stirring and mixing them evenly, and then extruding and molding them through a twin-screw extruder to obtain a TPU color-changing layer; step 2: adding the raw materials of the TPU self-repairing material into a mixer, stirring and mixing them evenly, and then extruding and molding them through a twin-screw extruder to obtain a TPU self-repairing layer; step 3: (1) stacking the TPU color-changing layer and the TPU self-repairing layer together, heating and fusing them; (2) evenly coating the outer surface of the TPU color-changing layer with a polyacrylate pressure-sensitive adhesive, and baking them to obtain a pressure-sensitive adhesive layer; (3) attaching a release film to the outer surface of the pressure-sensitive adhesive layer and the outer surface of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

Description

Technical Field

[0001] The present invention relates to the technical field of color-changing films, in particular to a self-repairing TPU color-changing film and a preparation process thereof. Background Art

[0002] Thermoplastic polyurethane (TPU) films are widely used in automotive color modification, electronic protection, architectural decoration, and other fields due to their excellent elasticity, wear resistance, and processing properties. However, traditional TPU films face multiple technical bottlenecks in practical use: First, the surface is easily damaged by mechanical scratches, resulting in deterioration of appearance and reduced protective performance. Conventional repair requires specialized equipment, and microcracks cannot be repaired independently. Second, the color-modified layer generally suffers from uneven pigment dispersion and poor weather resistance. Long-term exposure to ultraviolet light can easily lead to yellowing (yellowing index ΔYI > 5) and color migration (migration rate > 2%). Furthermore, multilayer composite film structures often experience interlayer delamination (180° peel strength < 8 N / cm) due to insufficient interfacial bonding, which is particularly pronounced under drastic temperature fluctuations. Although existing technologies attempt to improve performance by adding inorganic fillers or crosslinking agents, these often result in a loss of material flexibility (elongation at break drops to < 300%) or increased processing difficulty (melt flow index fluctuations > 30%).

[0003] Regarding the self-repair function, existing research focuses on introducing dynamic covalent bonds (such as Diels-Alder bonds and disulfide bonds), but the single chemical repair mechanism has defects such as high response temperature (>100°C) and low repair efficiency (<70%).

[0004] Based on this, the present invention aims to develop a self-repairing TPU color-changing film with high-efficiency self-repairing properties, excellent weather resistance and stable interlayer bonding strength, so as to break through the difficult problem of balancing functionality, durability and processability of traditional TPU films, and thus meet the long-term use needs in harsh outdoor environments. Summary of the Invention

[0005] The purpose of the present invention is to provide a self-repairing TPU color-changing film and a preparation process thereof to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A self-repairing TPU color-changing film, whose structure from bottom to top is a release film layer, a pressure-sensitive adhesive layer, a TPU color-changing layer, a TPU self-repairing layer, and a release film layer;

[0008] The release film layer is any one of a PET release film or a PP release film, and its thickness is 25-250 μm;

[0009] The pressure-sensitive adhesive layer is obtained by coating with a polyacrylate pressure-sensitive adhesive, and its thickness is 10-30 μm;

[0010] The TPU color-changing layer is obtained by extruding a TPU color-changing material, and its thickness is 10-20 μm;

[0011] The raw materials of the TPU color-changing material include the following components: 8 to 12 parts by weight of catechol-modified TPU resin, 6 to 8 parts of TPU masterbatch, 2 to 4 parts of modified titanium dioxide, 0.8 to 1.6 parts of dispersant, 0.2 to 0.4 parts of lubricant, and 0.2 to 0.4 parts of antioxidant;

[0012] The TPU self-repairing layer is obtained by extrusion molding of TPU self-repairing material, and its thickness is 100-150 μm;

[0013] The raw materials of the TPU self-repairing material include the following components: 12 to 20 parts by weight of catechol-modified TPU resin, 12 to 20 parts of disulfide-modified TPU resin, 2 to 4 parts of modified titanium dioxide, 1 to 2 parts of dispersant, 0.5 to 1 part of lubricant, and 0.5 to 1 part of antioxidant.

[0014] Furthermore, the catechol-modified TPU resin and the disulfide-modified TPU resin are obtained by modifying unsaturated TPU resin;

[0015] The preparation method of the unsaturated TPU resin is as follows: under nitrogen protection, isophorone diisocyanate, polytetramethylene glycol, polycarbonate diol, and N,N-dimethylformamide are added to a reaction kettle, stirred and mixed uniformly, and then dibutyltin dilaurate is added to the reaction system, and stirred and reacted at 65-80° C. for 1-6 hours; then 1,4-dihydroxy-2-butene is added to the reaction system, and stirred and reacted at the reaction temperature for 1-3 hours; finally, aminopropyl-terminated polydimethylsiloxane is added to the reaction system, and stirred and reacted at the reaction temperature for 1-3 hours, the reaction is terminated, and the unsaturated TPU resin is obtained by distillation under reduced pressure.

[0016] Furthermore, the raw materials required for preparing the unsaturated TPU resin include the following components: by weight, 16 to 24 parts of isophorone diisocyanate, 13.5 to 27 parts of polytetramethylene glycol, 13.5 to 27 parts of polycarbonate diol, 15 to 30 parts of N,N-dimethylformamide, 0.03 to 0.06 parts of dibutyltin dilaurate, 5.4 to 10.8 parts of 1,4-dihydroxy-2-butene, and 2.7 to 5.4 parts of aminopropyl-terminated polydimethylsiloxane.

[0017] Furthermore, the preparation method of the catechol-modified TPU resin is as follows: (1) under nitrogen protection, unsaturated TPU resin, 4-allylcatechol, and N,N-dimethylformamide are added to a reactor, stirred and mixed evenly, and then benzoyl peroxide is added dropwise to the reaction system at 60-80° C. while stirring. After the addition is completed, the stirring reaction is continued for 1-3 hours to terminate the reaction; (2) 2-furylmethylamine is added to (1), refluxed at room temperature for 1-6 hours, the reaction is terminated, and the catechol-modified TPU resin is obtained by vacuum distillation.

[0018] Furthermore, the raw materials required for preparing the catechol-modified TPU resin include the following components: 32 to 40 parts of unsaturated TPU resin, 6.4 to 12.8 parts of 4-allyl catechol, 0.008 to 0.016 parts of benzoyl peroxide, 2 to 4 parts of 2-furylamine, and 8 to 16 parts of N,N-dimethylformamide, in parts by weight.

[0019] Furthermore, the preparation method of the disulfide-modified TPU resin is as follows: under nitrogen protection, unsaturated TPU resin, difurfuryl disulfide, and N,N-dimethylformamide are added to a reactor, refluxed at room temperature for 1 to 6 hours, the reaction is terminated, and the disulfide-modified TPU resin is obtained by vacuum distillation.

[0020] Furthermore, the raw materials required for preparing the disulfide-modified TPU resin include the following components: 32 to 40 parts by weight of unsaturated TPU resin, 4.8 to 9.6 parts of difurfuryl disulfide, and 8 to 16 parts of N,N-dimethylformamide.

[0021] Furthermore, the preparation method of the TPU masterbatch is: adding catechol-modified TPU resin, nylon 6, pigment, compatibilizer, and dispersant into a mixer, stirring and mixing them evenly, and then extruding and granulating them through a twin-screw extruder to obtain TPU masterbatch.

[0022] Furthermore, the raw materials required for preparing the TPU masterbatch include the following components: by weight, 2-4 parts of catechol-modified TPU resin, 2-4 parts of nylon 6, 4-8 parts of pigment, 0.4-1.2 parts of compatibilizer, and 0.4-1.2 parts of dispersant.

[0023] Furthermore, the compatibilizer is polyacrylic acid grafted with maleic anhydride.

[0024] Furthermore, the preparation method of the modified titanium dioxide is: adding titanium dioxide and 3-aminopropyltriethoxysilane to a 60-80 wt% ethanol aqueous solution, stirring and reacting at 40-70° C. for 1-6 hours, and drying the discharged material to obtain modified silicon dioxide.

[0025] Furthermore, the mass ratio of the titanium dioxide to 3-aminopropyltriethoxysilane is 1:(0.01~0.1).

[0026] Furthermore, in an embodiment of the present invention, the extrusion parameters of the twin-screw extruder are as follows: the extruder has six sections, the temperature range of each section is 180-215° C., and the screw speed is 250-350 r / min.

[0027] Furthermore, the preparation process of the self-repairing TPU color-changing film comprises the following steps:

[0028] Step 1: Add the raw materials of TPU color-changing material into a mixer, stir and mix evenly, and then extrude through a twin-screw extruder to obtain a TPU color-changing layer;

[0029] Step 2: Add the raw materials of TPU self-repairing material into a mixer, stir and mix them evenly, and then extrude them through a twin-screw extruder to obtain a TPU self-repairing layer;

[0030] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together and heat and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer and bake to obtain a pressure-sensitive adhesive layer; (3) Attach a release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0031] Furthermore, the parameters of the heating fusion are: temperature of 190-200° C., pressure of 0.5-1.2 MPa, and time of 15-30 s.

[0032] In the present invention, isophorone diisocyanate is first reacted with two diols, polytetramethylene glycol and polycarbonate diol, and then 1,4-dihydroxy-2-butene is added to extend the chain and aminopropyl-terminated polydimethylsiloxane is added to cap the end, ultimately preparing an unsaturated TPU resin. The reason for using two diols in a composite is that polytetramethylene glycol contains an ether bond, which can give the color-changing film a certain resilience and toughness, making it have good flexibility even at low temperatures. Polycarbonate diol contains carbonate groups, which have good stability and can enhance the tensile strength and high-temperature resistance of the color-changing film. Through the synergistic effect of the two diols, the color-changing film has good mechanical properties and high and low temperature resistance. The purpose of 1,4-dihydroxy-2-butene is to introduce unsaturated double bonds to facilitate subsequent modification and grafting; the purpose of aminopropyl-terminated polydimethylsiloxane is to introduce polydimethylsiloxane chain ends, which can give the color-changing film hydrophobic properties and further improve the high and low temperature resistance of the color-changing film. At the same time, the polydimethylsiloxane chain ends can also play a lubricating role in the processing process, reduce friction and wear, and help the processing.

[0033] In the present invention, catechol-modified TPU resin, TPU masterbatch, modified titanium dioxide and other additives are melt-extruded to obtain a TPU color-changing layer. Among them, the catechol-modified TPU resin is obtained by free radical polymerization of 4-allyl catechol and unsaturated TPU resin, and then reacting with 2-furylamine; the carbon-carbon double bond in the 4-allyl catechol group and the carbon-carbon double bond in the unsaturated TPU resin can form a covalent cross-linked network, which has a certain improvement effect on the tensile properties of the color-changing film; secondly, the catechol-based structure is introduced into the catechol-modified TPU resin, which can achieve the following purposes: (1) The catechol group has the effect of improving the antioxidant performance, which is further synergistic. Antioxidants can greatly prevent the TPU color-changing layer and TPU self-repairing layer from yellowing and becoming brittle due to sunlight; (2) The catechol group contains abundant phenolic hydroxyl groups, which in turn allows the TPU color-changing layer, TPU self-repairing layer, and pressure-sensitive adhesive layer to form hydrogen bonds, strengthening the connection between the layers and effectively preventing the peeling of the layers, ensuring the structural stability of the color-changing film during long-term use; (3) The hydroxyl groups of the catechol group can also form hydrogen bonds with the carbamate groups in the resin, which can also give the color-changing film self-repairing ability to a certain extent. Secondly, the scheme uses 2-furanmethylamine as the end-capping agent of the catechol-TPU resin, which not only avoids the problem of residual unsaturated bonds being oxidized by ultraviolet light, resulting in the attenuation of the color-changing film performance, but also the furan structure can form a DA dynamic structure with the double bond, which can enhance the self-repairing ability of the color-changing film. Furthermore, amino groups are introduced to strengthen the hydrogen bonding between the resins, thereby enhancing the self-repairing performance of the TPU color-changing film.

[0034] The TPU masterbatch is obtained by melt extrusion of catechol-modified TPU resin, nylon 6, pigment, compatibilizer, and dispersant. Under the action of the compatibilizer, nylon 6 can be used as a dispersing aid, allowing the pigment to be better dispersed in the catechol-modified TPU resin, ultimately obtaining a masterbatch with stable and uniform coloring. The modified titanium dioxide is modified with 3-aminopropyltriethoxysilane. The amino group it contains can form hydrogen bonds with catechol-modified TPU resin or disulfide-modified TPU resin, which can improve the mechanical properties of the color-changing film. At the same time, it can also improve the ultraviolet shielding ability of the color-changing film. It cooperates with the catechol group in the catechol-modified TPU resin to prevent the TPU color-changing layer and TPU self-repairing layer from yellowing and brittleness due to sunlight.

[0035] In the present invention, difurfuryl disulfide is further subjected to a free radical polymerization reaction with an unsaturated TPU resin. Difurfuryl disulfide acts as a linker, and its furan structure can be linked to unsaturated TPU resins of different chains, thereby imparting to the prepared color-changing film improved toughness and self-healing properties. The prepared disulfide-modified TPU resin contains a disulfide bond structure and a DA dynamic structure, which can impart excellent self-healing properties to the color-changing film.

[0036] The DA dynamic structure is further formed, which not only strengthens the fusion of the raw material components, but also further enhances the self-repairing properties of the color-changing film.

[0037] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0038] (1) The self-repairing TPU color-changing film prepared by the present invention has excellent self-repairing properties, mechanical properties, high and low temperature resistance and antioxidant properties and stable performance, which solves the deficiencies of traditional TPU color-changing films in terms of functionality and weather resistance, and can better meet the needs of long-term outdoor use;

[0039] (2) The self-repairing TPU color-changing film prepared by the present invention has a tight bond between the various layers of the film and will not peel off after long-term use, thus ensuring the service life of the self-repairing TPU color-changing film;

[0040] (3) The self-repairing TPU color-changing film prepared by the present invention has uniform coloring, small color difference and excellent overall quality. DETAILED DESCRIPTION

[0041] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0042] It should be noted that the following parts are calculated by weight, and the purchasers of all raw materials involved in the present invention include, without any special restrictions, the following examples:

[0043] In the following examples, isophorone diisocyanate with a purity of 99%, polytetrahydrofuran diol with a purity of 99.5% and a molecular weight of 1000, polycarbonate diol with a purity of 99% and a molecular weight of 1000, and 2-furfurylamine with a purity of 98% were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0044] 1,4-dihydroxy-2-butene with a purity of 99.5%, aminopropyl-terminated polydimethylsiloxane with a purity of 99.5% and a molecular weight of 1000, polydimethylsiloxane with a purity of 99% and a molecular weight of 1000, 3-aminopropyltriethoxysilane with a purity of 99.5%, titanium dioxide with a purity of 99.5% and a particle size of 20-50 nm, oxidized polyethylene wax with a purity of 99.5%, and antioxidant 1076 with a purity of 99% were purchased from Hubei Wonder Chemical Co., Ltd.

[0045] 4-Allylcatechol was purchased from Zhengzhou Alpha Chemical Co., Ltd. with a purity of 98%;

[0046] Nylon 6 with a purity of 99%, product number: S45091, was purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0047] Polyacrylic acid grafted maleic anhydride with a purity of 95% was purchased from Xi'an Ruixi Biotechnology Co., Ltd.

[0048] Difurfuryl disulfide was 98% pure and purchased from JACS-Zhengzhou Jacks Chemical Products Co., Ltd.

[0049] Polyacrylate pressure-sensitive adhesive, brand Chemlock, purchased from Yueyang Baoling Industry and Trade Co., Ltd.

[0050] PET release film, 50 μm thick, was purchased from Shenzhen Yuanxin Film Co., Ltd.; the rest were commercially available; each portion in the examples was 100 g.

[0051] Example 1: Preparation process of a self-repairing TPU color-changing film:

[0052] Step 1: Prepare TPU color-changing layer:

[0053] S11: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 8 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 3.5 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0054] S12: Preparation of catechol-modified TPU resin: (1) Under nitrogen protection, 36 parts of unsaturated TPU resin, 9.5 parts of 4-allylcatechol, and 12 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.01 parts of benzoyl peroxide were added dropwise to the reaction system at 70°C while stirring. After the addition was completed, the reaction was continued with stirring for 3 hours to terminate the reaction. (2) 3 parts of 2-furylmethylamine were added to (1), and the reaction was refluxed at room temperature for 6 hours to terminate the reaction. The catechol-modified TPU resin was obtained by distillation under reduced pressure.

[0055] S13: Preparing TPU masterbatch: adding catechol-modified TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing them uniformly, and then extruding and pelletizing them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain TPU masterbatch;

[0056] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of catechol-modified TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0057] S14: Preparation of modified titanium dioxide: 8 parts of titanium dioxide and 0.4 parts of 3-aminopropyltriethoxysilane were added to an appropriate amount of 70 wt% ethanol aqueous solution, stirred and reacted at 60° C. for 6 h, and the discharged material was dried to obtain modified silicon dioxide;

[0058] S15: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0059] The raw materials of the TPU color-changing material include the following components: by weight, 10 parts of catechol-modified TPU resin, 7 parts of TPU masterbatch, 3 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0060] Step 2: Preparation of TPU self-repairing layer:

[0061] S21: Preparation of disulfide-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 8 parts of difurfuryl disulfide, and 12 parts of N,N-dimethylformamide were added to a reactor, and the mixture was refluxed at room temperature for 6 hours. The reaction was terminated, and the disulfide-modified TPU resin was obtained by vacuum distillation.

[0062] S22: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0063] The raw materials of the TPU self-repairing material include the following components: 15 parts of catechol-modified TPU resin, 15 parts of disulfide-modified TPU resin, 3 parts of modified titanium dioxide, 1.5 parts of oxidized polyethylene wax, 0.8 parts of polydimethylsiloxane, and 0.8 parts of antioxidant 1076, calculated by weight;

[0064] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0065] Example 2: Preparation process of a self-repairing TPU color-changing film:

[0066] Step 1: Prepare TPU color-changing layer:

[0067] S11: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 5.4 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 2.7 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0068] S12: Preparation of catechol-modified TPU resin: (1) Under nitrogen protection, 36 parts of unsaturated TPU resin, 6.4 parts of 4-allylcatechol, and 12 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.01 parts of benzoyl peroxide were added dropwise to the reaction system at 70°C while stirring. After the addition was completed, the reaction was continued with stirring for 3 hours to terminate the reaction. (2) 2 parts of 2-furylmethylamine were added to (1), and the reaction was refluxed at room temperature for 6 hours to terminate the reaction. The catechol-modified TPU resin was obtained by distillation under reduced pressure.

[0069] S13: Preparing TPU masterbatch: adding catechol-modified TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing them uniformly, and then extruding and pelletizing them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain TPU masterbatch;

[0070] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of catechol-modified TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0071] S14: preparing modified titanium dioxide: adding 8 parts of titanium dioxide and 0.08 parts of 3-aminopropyltriethoxysilane to an appropriate amount of 70 wt % ethanol aqueous solution, stirring and reacting at 60° C. for 6 h, and drying the discharged material to obtain modified silicon dioxide;

[0072] S15: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0073] The raw materials of the TPU color-changing material include the following components: 8 parts by weight of catechol-modified TPU resin, 7 parts of TPU masterbatch, 2 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0074] Step 2: Preparation of TPU self-repairing layer:

[0075] S21: Preparation of disulfide-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 4.8 parts of difurfuryl disulfide, and 12 parts of N,N-dimethylformamide were added to a reactor, and the mixture was refluxed at room temperature for 6 hours. The reaction was terminated, and the disulfide-modified TPU resin was obtained by vacuum distillation.

[0076] S22: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0077] The raw materials of the TPU self-repairing material include the following components: 12 parts by weight of catechol-modified TPU resin, 12 parts by weight of disulfide-modified TPU resin, 2 parts by weight of modified titanium dioxide, 1.5 parts by weight of oxidized polyethylene wax, 0.8 parts by weight of polydimethylsiloxane, and 0.8 parts by weight of antioxidant 1076;

[0078] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0079] Example 3: Preparation process of a self-repairing TPU color-changing film:

[0080] Step 1: Prepare TPU color-changing layer:

[0081] S11: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 10.8 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 5.4 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0082] S12: Preparation of catechol-modified TPU resin: (1) Under nitrogen protection, 36 parts of unsaturated TPU resin, 12.8 parts of 4-allylcatechol, and 12 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.01 parts of benzoyl peroxide were added dropwise to the reaction system at 70°C while stirring. After the addition was completed, the reaction was continued with stirring for 3 hours to terminate the reaction. (2) 4 parts of 2-furylmethylamine were added to (1), and the reaction was refluxed at room temperature for 6 hours to terminate the reaction. The catechol-modified TPU resin was obtained by distillation under reduced pressure.

[0083] S13: Preparing TPU masterbatch: adding catechol-modified TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing them uniformly, and then extruding and pelletizing them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain TPU masterbatch;

[0084] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of catechol-modified TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0085] S14: Preparation of modified titanium dioxide: 8 parts of titanium dioxide and 0.8 parts of 3-aminopropyltriethoxysilane were added to an appropriate amount of 70 wt% ethanol aqueous solution, stirred and reacted at 60° C. for 6 h, and the discharged material was dried to obtain modified silicon dioxide;

[0086] S15: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0087] The raw materials of the TPU color-changing material include the following components: by weight, 12 parts of catechol-modified TPU resin, 7 parts of TPU masterbatch, 4 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0088] Step 2: Preparation of TPU self-repairing layer:

[0089] S21: Preparation of disulfide-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 9.6 parts of difurfuryl disulfide, and 12 parts of N,N-dimethylformamide were added to a reactor, and the mixture was refluxed at room temperature for 6 hours. The reaction was terminated, and the disulfide-modified TPU resin was obtained by vacuum distillation.

[0090] S22: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0091] The raw materials of the TPU self-repairing material include the following components: 20 parts by weight of catechol-modified TPU resin, 20 parts by weight of disulfide-modified TPU resin, 4 parts by weight of modified titanium dioxide, 1.5 parts by weight of oxidized polyethylene wax, 0.8 parts by weight of polydimethylsiloxane, and 0.8 parts by weight of antioxidant 1076;

[0092] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0093] The following control experiments are conducted based on Example 1, and comparative examples 1 to 6 are set as follows:

[0094] Comparative Example 1: Comparative Example 1 is based on Example 1, with the following adjustments: catechol-modified TPU resin and disulfide-modified TPU resin are directly replaced by commercially available TPU, and other processes remain unchanged, specifically:

[0095] A preparation process of self-repairing TPU color-changing film:

[0096] Step 1: Prepare TPU color-changing layer:

[0097] S11: Preparing TPU masterbatch: adding TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing uniformly, and then extruding and pelletizing through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain TPU masterbatch;

[0098] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0099] S12: Preparation of modified titanium dioxide: 8 parts of titanium dioxide and 0.4 parts of 3-aminopropyltriethoxysilane were added to an appropriate amount of 70 wt% ethanol aqueous solution, stirred and reacted at 60° C. for 6 h, and the discharged material was dried to obtain modified silicon dioxide;

[0100] S13: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0101] The raw materials of the TPU color-changing material include the following components: by weight, 10 parts of TPU resin, 7 parts of TPU masterbatch, 3 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0102] Step 2: Preparation of TPU self-repairing layer:

[0103] S21: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0104] The raw materials of the TPU self-repairing material include the following components: 30 parts of TPU resin, 3 parts of modified titanium dioxide, 1.5 parts of oxidized polyethylene wax, 0.8 parts of polydimethylsiloxane, and 0.8 parts of antioxidant 1076, calculated by weight;

[0105] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0106] Comparative Example 2: Comparative Example 2 is based on Example 1, with the following adjustments: catechol-modified TPU resin is replaced by commercially available TPU resin, and other processes remain unchanged, specifically:

[0107] A preparation process of self-repairing TPU color-changing film:

[0108] Step 1: Prepare TPU color-changing layer:

[0109] S11: Preparing TPU masterbatch: adding TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing uniformly, and then extruding and pelletizing through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain TPU masterbatch;

[0110] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0111] S12: Preparation of modified titanium dioxide: 8 parts of titanium dioxide and 0.4 parts of 3-aminopropyltriethoxysilane were added to an appropriate amount of 70 wt% ethanol aqueous solution, stirred and reacted at 60° C. for 6 h, and the discharged material was dried to obtain modified silicon dioxide;

[0112] S13: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0113] The raw materials of the TPU color-changing material include the following components: by weight, 10 parts of TPU resin, 7 parts of TPU masterbatch, 3 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0114] Step 2: Preparation of TPU self-repairing layer:

[0115] S21: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 8 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 3.5 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0116] S22: Preparation of disulfide-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 8 parts of difurfuryl disulfide, and 12 parts of N,N-dimethylformamide were added to a reactor, and the mixture was refluxed at room temperature for 6 hours. The reaction was terminated, and the disulfide-modified TPU resin was obtained by vacuum distillation.

[0117] S23: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0118] The raw materials of the TPU self-repairing material include the following components: by weight, 15 parts of TPU resin, 15 parts of disulfide-modified TPU resin, 3 parts of modified titanium dioxide, 1.5 parts of oxidized polyethylene wax, 0.8 parts of polydimethylsiloxane, and 0.8 parts of antioxidant 1076;

[0119] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0120] Comparative Example 3: Comparative Example 3 is based on Example 1, with the following adjustments: disulfide-modified TPU resin is replaced by commercially available TPU resin, and other processes remain unchanged, specifically:

[0121] A preparation process of self-repairing TPU color-changing film:

[0122] Step 1: Prepare TPU color-changing layer:

[0123] S11: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 8 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 3.5 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0124] S12: Preparation of catechol-modified TPU resin: (1) Under nitrogen protection, 36 parts of unsaturated TPU resin, 9.5 parts of 4-allylcatechol, and 12 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.01 parts of benzoyl peroxide were added dropwise to the reaction system at 70°C while stirring. After the addition was completed, the reaction was continued with stirring for 3 hours to terminate the reaction. (2) 3 parts of 2-furylmethylamine were added to (1), and the reaction was refluxed at room temperature for 6 hours to terminate the reaction. The catechol-modified TPU resin was obtained by distillation under reduced pressure.

[0125] S13: Preparing TPU masterbatch: adding catechol-modified TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing them uniformly, and then extruding and pelletizing them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain TPU masterbatch;

[0126] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of catechol-modified TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0127] S14: Preparation of modified titanium dioxide: 8 parts of titanium dioxide and 0.4 parts of 3-aminopropyltriethoxysilane were added to an appropriate amount of 70 wt% ethanol aqueous solution, stirred and reacted at 60° C. for 6 h, and the discharged material was dried to obtain modified silicon dioxide;

[0128] S15: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0129] The raw materials of the TPU color-changing material include the following components: by weight, 10 parts of catechol-modified TPU resin, 7 parts of TPU masterbatch, 3 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0130] Step 2: Preparation of TPU self-repairing layer:

[0131] S21: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0132] The raw materials of the TPU self-repairing material include the following components: 15 parts of catechol-modified TPU resin, 15 parts of TPU resin, 3 parts of modified titanium dioxide, 1.5 parts of oxidized polyethylene wax, 0.8 parts of polydimethylsiloxane, and 0.8 parts of antioxidant 1076, calculated by weight;

[0133] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0134] Comparative Example 4: Comparative Example 4 is based on Example 1, with the following adjustments: no modified titanium dioxide is added, and other processes remain unchanged, specifically:

[0135] A preparation process of self-repairing TPU color-changing film:

[0136] Step 1: Prepare TPU color-changing layer:

[0137] S11: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 8 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 3.5 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0138] S12: Preparation of catechol-modified TPU resin: (1) Under nitrogen protection, 36 parts of unsaturated TPU resin, 9.5 parts of 4-allylcatechol, and 12 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.01 parts of benzoyl peroxide were added dropwise to the reaction system at 70°C while stirring. After the addition was completed, the reaction was continued with stirring for 3 hours to terminate the reaction. (2) 3 parts of 2-furylmethylamine were added to (1), and the reaction was refluxed at room temperature for 6 hours to terminate the reaction. The catechol-modified TPU resin was obtained by distillation under reduced pressure.

[0139] S13: Preparing TPU masterbatch: adding catechol-modified TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing them uniformly, and then extruding and pelletizing them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain TPU masterbatch;

[0140] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of catechol-modified TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0141] S14: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0142] The raw materials of the TPU color-changing material include the following components: 10 parts by weight of catechol-modified TPU resin, 7 parts of TPU masterbatch, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0143] Step 2: Preparation of TPU self-repairing layer:

[0144] S21: Preparation of disulfide-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 8 parts of difurfuryl disulfide, and 12 parts of N,N-dimethylformamide were added to a reactor, and the mixture was refluxed at room temperature for 6 hours. The reaction was terminated, and the disulfide-modified TPU resin was obtained by vacuum distillation.

[0145] S22: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0146] The raw materials of the TPU self-repairing material include the following components: 15 parts of catechol-modified TPU resin, 15 parts of disulfide-modified TPU resin, 1.5 parts of oxidized polyethylene wax, 0.8 parts of polydimethylsiloxane, and 10760.8 parts of antioxidant, calculated by weight;

[0147] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0148] Comparative Example 5: Comparative Example 5 is based on Example 1, with the following adjustments: 4-allylcatechol is not added, and other processes remain unchanged, specifically:

[0149] A preparation process of self-repairing TPU color-changing film:

[0150] Step 1: Prepare TPU color-changing layer:

[0151] S11: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 8 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 3.5 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0152] S12: Preparation of catechol-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 3 parts of 2-furylamine, and 12 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.01 parts of benzoyl peroxide was added dropwise to the reaction system at 70°C while stirring. After the addition was complete, the reaction was continued with stirring for 3 hours. The reaction was terminated and the catechol-modified TPU resin was obtained by distillation under reduced pressure.

[0153] S13: Preparing TPU masterbatch: adding catechol-modified TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and oxidized polyethylene wax into a mixer, stirring and mixing them uniformly, and then extruding and pelletizing them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain TPU masterbatch;

[0154] The TPU masterbatch comprises the following raw material components: by weight, 3 parts of catechol-modified TPU resin, 3 parts of nylon 6, 6 parts of pigment, 1 part of polyacrylic acid grafted maleic anhydride, and 1 part of oxidized polyethylene wax;

[0155] S14: Preparation of modified titanium dioxide: 8 parts of titanium dioxide and 0.4 parts of 3-aminopropyltriethoxysilane were added to an appropriate amount of 70 wt% ethanol aqueous solution, stirred and reacted at 60° C. for 6 h, and the discharged material was dried to obtain modified silicon dioxide;

[0156] S15: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0157] The raw materials of the TPU color-changing material include the following components: by weight, 10 parts of catechol-modified TPU resin, 7 parts of TPU masterbatch, 3 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0158] Step 2: Preparation of TPU self-repairing layer:

[0159] S21: Preparation of disulfide-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 8 parts of difurfuryl disulfide, and 12 parts of N,N-dimethylformamide were added to a reactor, and the mixture was refluxed at room temperature for 6 hours. The reaction was terminated, and the disulfide-modified TPU resin was obtained by vacuum distillation.

[0160] S22: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0161] The raw materials of the TPU self-repairing material include the following components: 15 parts of catechol-modified TPU resin, 15 parts of disulfide-modified TPU resin, 3 parts of modified titanium dioxide, 1.5 parts of oxidized polyethylene wax, 0.8 parts of polydimethylsiloxane, and 0.8 parts of antioxidant 1076, calculated by weight;

[0162] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0163] Comparative Example 6: Comparative Example 6 is based on Example 1, with the following adjustments: nylon 6 is not added to the TPU masterbatch, and other processes remain unchanged, specifically:

[0164] A preparation process of self-repairing TPU color-changing film:

[0165] Step 1: Prepare TPU color-changing layer:

[0166] S11: Preparation of unsaturated TPU resin: Under nitrogen protection, 20 parts of isophorone diisocyanate, 18 parts of polytetramethylene glycol, 18 parts of polycarbonate diol, and 25 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.05 parts of dibutyltin dilaurate were added to the reaction system, and the mixture was stirred and reacted at 75°C for 6 hours. Then, 8 parts of 1,4-dihydroxy-2-butene were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. Finally, 3.5 parts of aminopropyl-terminated polydimethylsiloxane were added to the reaction system, and the reaction temperature was maintained and stirred for 3 hours. The reaction was terminated and the mixture was distilled under reduced pressure to obtain an unsaturated TPU resin.

[0167] S12: Preparation of catechol-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 9.5 parts of 4-allylcatechol, and 12 parts of N,N-dimethylformamide were added to a reactor and stirred to mix evenly. Then, 0.01 parts of benzoyl peroxide were added dropwise to the reaction system at 70°C while stirring. After the addition was completed, the reaction was continued with stirring for 3 hours to terminate the reaction. (2) 3 parts of 2-furylmethylamine were added to (1), and the reaction was refluxed at room temperature for 6 hours to terminate the reaction. The catechol-modified TPU resin was obtained by distillation under reduced pressure.

[0168] S13: Preparing TPU masterbatch: adding catechol-modified TPU resin, pigment, and oxidized polyethylene wax into a mixer, stirring and mixing them uniformly, and then extruding and pelletizing them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain TPU masterbatch;

[0169] The TPU masterbatch comprises the following raw material components: 3 parts by weight of catechol-modified TPU resin, 6 parts of pigment, and 1 part of oxidized polyethylene wax;

[0170] S14: Preparation of modified titanium dioxide: 8 parts of titanium dioxide and 0.4 parts of 3-aminopropyltriethoxysilane were added to an appropriate amount of 70 wt% ethanol aqueous solution, stirred and reacted at 60° C. for 6 h, and the discharged material was dried to obtain modified silicon dioxide;

[0171] S15: Add the raw materials of the TPU color-changing material into a mixer, stir and mix them evenly, and then form them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300r / min to obtain a 15μm thick TPU color-changing layer;

[0172] The raw materials of the TPU color-changing material include the following components: by weight, 10 parts of catechol-modified TPU resin, 7 parts of TPU masterbatch, 3 parts of modified titanium dioxide, 1.2 parts of oxidized polyethylene wax, 0.3 parts of polydimethylsiloxane, and 0.3 parts of antioxidant 1076;

[0173] Step 2: Preparation of TPU self-repairing layer:

[0174] S21: Preparation of disulfide-modified TPU resin: Under nitrogen protection, 36 parts of unsaturated TPU resin, 8 parts of difurfuryl disulfide, and 12 parts of N,N-dimethylformamide were added to a reactor, and the mixture was refluxed at room temperature for 6 hours. The reaction was terminated, and the disulfide-modified TPU resin was obtained by vacuum distillation.

[0175] S22: adding the raw materials of the TPU self-healing material into a mixer, stirring and mixing them uniformly, and then extruding them through a twin-screw extruder. The extrusion temperature of each section of the twin-screw extruder is controlled at 190±5°C and the screw speed is 300 r / min to obtain a 120 μm thick TPU self-healing layer.

[0176] The raw materials of the TPU self-repairing material include the following components: 15 parts of catechol-modified TPU resin, 15 parts of disulfide-modified TPU resin, 3 parts of modified titanium dioxide, 1.5 parts of oxidized polyethylene wax, 0.8 parts of polydimethylsiloxane, and 0.8 parts of antioxidant 1076, calculated by weight;

[0177] Step 3: (1) Stack the TPU color-changing layer and the TPU self-repairing layer together, heat to 195°C, apply a pressure of 0.8 MPa, hold for 20 seconds, and fuse them; (2) Apply polyacrylate pressure-sensitive adhesive evenly to the outer side of the TPU color-changing layer, heat to 100°C, and bake for 5 minutes to obtain a 15 μm thick pressure-sensitive adhesive layer; (3) Attach a 50 μm thick PET release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film.

[0178] Performance test: The self-repairing TPU color-changing films prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were subjected to relevant performance tests. The specific test items are as follows:

[0179] 1. Weather resistance: Four groups of samples were selected from the self-healing TPU color-changing films corresponding to each example. After removing the release film, the four groups of samples were placed in -30°C, room temperature, and 80°C environments for 2 hours, and in an accelerated aging chamber irradiated with a 200W mercury light source for 360 hours. The samples were then immediately taken out and subjected to tensile strength tests according to GB / T 1040.1-2018.

[0180] 2. Color difference uniformity: After removing the release film from the self-repairing TPU color-changing film corresponding to each example, use a spectrophotometer to measure the color difference, take 5 points, and calculate the average value;

[0181] 3. Self-repairing performance test: (1) After removing the release film on the self-repairing TPU color-changing film corresponding to each example, use 600-grit sandpaper to perform linear friction on the TPU self-repairing layer of the self-repairing TPU color-changing film, with a load of 500g, a stroke of 10cm, and 5 reciprocating times. Then use a gloss meter to test the gloss of the polished self-repairing TPU color-changing film; (2) Place the polished self-repairing TPU color-changing film at 60℃ for 2h, wait for it to return to room temperature, and then use a gloss meter to test its gloss. By comparing the changes in gloss before and after, the self-repairing performance of the self-repairing TPU color-changing film can be judged.

[0182] The specific data of the above test items are shown in Table 1 below:

[0183]

[0184] Conclusion: It can be seen from the data in Table 1 above that the catechol-modified TPU resin prepared by the reaction of 4-allylcatechol, 2-furylamine and unsaturated TPU resin, and the disulfide-modified TPU resin prepared by the reaction of difurfuryl disulfide and unsaturated TPU resin, can play a positive synergistic role, so that the processed self-repairing TPU color-changing film has excellent mechanical properties, weather resistance, coloring uniformity and self-repairing properties. At the same time, modified titanium dioxide can be added to enhance its performance, and finally a high-quality self-repairing TPU color-changing film with excellent comprehensive performance is prepared, which is more suitable for outdoor use.

[0185] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A preparation process for a self-repairing TPU color-changing film, characterized by: The following steps are involved: Step 1: Add the raw materials of TPU color-changing material into a mixer, stir and mix evenly, and then extrude through a twin-screw extruder to obtain a TPU color-changing layer; Step 2: Add the raw materials of TPU self-repairing material into a mixer, stir and mix them evenly, and then extrude them through a twin-screw extruder to obtain a TPU self-repairing layer; Step 3: (1) stacking the TPU color-changing layer and the TPU self-repairing layer together and heating and fusing them; (2) evenly coating the polyacrylate pressure-sensitive adhesive on the outer side of the TPU color-changing layer and baking them to obtain a pressure-sensitive adhesive layer; (3) attaching a release film to the outer side of the pressure-sensitive adhesive layer and the outer side of the TPU self-repairing layer to obtain a self-repairing TPU color-changing film; The raw materials of the TPU color-changing material include the following components: 8 to 12 parts by weight of catechol-modified TPU resin, 6 to 8 parts of TPU masterbatch, 2 to 4 parts of modified titanium dioxide, 0.8 to 1.6 parts of dispersant, 0.2 to 0.4 parts of lubricant, and 0.2 to 0.4 parts of antioxidant; wherein the raw materials of the TPU masterbatch include the following components: 2 to 4 parts by weight of catechol-modified TPU resin, 2 to 4 parts of nylon 6, 4 to 8 parts of pigment, 0.4 to 1.2 parts of polyacrylic acid grafted maleic anhydride, and 0.4 to 1.2 parts of dispersant; The raw materials of the TPU self-repairing material include the following components: 12 to 20 parts by weight of catechol-modified TPU resin, 12 to 20 parts by weight of disulfide-modified TPU resin, 2 to 4 parts by weight of modified titanium dioxide, 1 to 2 parts by weight of dispersant, 0.5 to 1 part by weight of lubricant, and 0.5 to 1 part by weight of antioxidant; The catechol-modified TPU resin and the disulfide-modified TPU resin are both obtained by modifying unsaturated TPU resin; The preparation method of catechol-modified TPU resin is as follows: (1) under nitrogen protection, unsaturated TPU resin, 4-allylcatechol and N,N-dimethylformamide are added to a reactor, stirred and mixed evenly, and then benzoyl peroxide is added dropwise to the reaction system at 60-80°C while stirring. After the addition is completed, the stirring reaction is continued for 1-3 hours to terminate the reaction; (2) 2-furylamine is added to (1), refluxed at room temperature for 1-6 hours, the reaction is terminated, and the catechol-modified TPU resin is obtained by vacuum distillation.

2. The preparation process of the self-repairing TPU color-changing film according to claim 1, characterized in that: The preparation method of the unsaturated TPU resin comprises: adding isophorone diisocyanate, polytetramethylene glycol, polycarbonate diol, and N,N-dimethylformamide to a reaction kettle under nitrogen protection, stirring and mixing uniformly, then adding dibutyltin dilaurate to the reaction system, stirring and reacting at 65-80° C. for 1-6 hours; then adding 1,4-dihydroxy-2-butene to the reaction system, maintaining the reaction temperature and stirring and reacting for 1-3 hours; finally, adding aminopropyl-terminated polydimethylsiloxane to the reaction system, maintaining the reaction temperature and stirring and reacting for 1-3 hours, terminating the reaction, and performing reduced pressure distillation to obtain the unsaturated TPU resin; Among them, the raw materials required for the preparation of unsaturated TPU resin include the following components: by weight, 16 to 24 parts of isophorone diisocyanate, 13.5 to 27 parts of polytetramethylene glycol, 13.5 to 27 parts of polycarbonate diol, 15 to 30 parts of N,N-dimethylformamide, 0.03 to 0.06 parts of dibutyltin dilaurate, 5.4 to 10.8 parts of 1,4-dihydroxy-2-butene, and 2.7 to 5.4 parts of aminopropyl-terminated polydimethylsiloxane.

3. The preparation process of the self-repairing TPU color-changing film according to claim 1, characterized in that: The raw materials required for preparing the catechol-modified TPU resin include the following components: 32 to 40 parts of unsaturated TPU resin, 6.4 to 12.8 parts of 4-allyl catechol, 0.008 to 0.016 parts of benzoyl peroxide, 2 to 4 parts of 2-furylamine, and 8 to 16 parts of N,N-dimethylformamide, calculated by weight.

4. The preparation process of the self-repairing TPU color-changing film according to claim 1, characterized in that: The preparation method of the disulfide-modified TPU resin comprises: adding unsaturated TPU resin, difurfuryl disulfide, and N,N-dimethylformamide to a reactor under nitrogen protection, performing reflux reaction at room temperature for 1 to 6 hours, terminating the reaction, and performing reduced pressure distillation to obtain the disulfide-modified TPU resin; The raw materials required for preparing the disulfide-modified TPU resin include the following components: 32 to 40 parts of unsaturated TPU resin, 4.8 to 9.6 parts of difurfuryl disulfide, and 8 to 16 parts of N,N-dimethylformamide, calculated by weight.

5. The preparation process of the self-repairing TPU color-changing film according to claim 1, characterized in that: The preparation method of the TPU masterbatch is as follows: catechol-modified TPU resin, nylon 6, pigment, polyacrylic acid grafted maleic anhydride, and dispersant are added into a mixer, stirred and mixed evenly, and then extruded and granulated through a twin-screw extruder to obtain the TPU masterbatch.

6. The process for preparing a self-repairing TPU color-changing film according to claim 1, characterized in that: The modified titanium dioxide is prepared by adding titanium dioxide and 3-aminopropyltriethoxysilane to a 60-80 wt% ethanol aqueous solution, stirring and reacting at 40-70° C. for 1-6 hours, and drying the discharged material to obtain the modified silicon dioxide. Wherein, the mass ratio of titanium dioxide and 3-aminopropyltriethoxysilane is 1:(0.01~0.1).

7. The process for preparing a self-repairing TPU color-changing film according to claim 1 or 5, characterized in that: The extrusion parameters of the twin-screw extruder are as follows: the extruder has six sections, the temperature range of each section is 180-215° C., and the screw speed is 250-350 r / min.

8. The process for preparing a self-repairing TPU color-changing film according to claim 1, characterized in that: The parameters of the heating fusion are: temperature of 190-200° C., pressure of 0.5-1.2 MPa, and time of 15-30 seconds.

9. A self-repairing TPU color-changing film prepared according to the preparation process of a self-repairing TPU color-changing film according to any one of claims 1 to 8.

10. The self-repairing TPU color-changing film according to claim 9, characterized in that: The structure of the self-repairing TPU color-changing film is, from bottom to top, a release film layer, a pressure-sensitive adhesive layer, a TPU color-changing layer, a TPU self-repairing layer, and a release film layer; The release film layer is any one of a PET release film or a PP release film, and its thickness is 25-250 μm; The pressure-sensitive adhesive layer is obtained by coating with a polyacrylate pressure-sensitive adhesive, and its thickness is 10-30 μm; The TPU color-changing layer is obtained by extruding a TPU color-changing material, and its thickness is 10-20 μm; The TPU self-repairing layer is obtained by extruding a TPU self-repairing material and has a thickness of 100-150 μm.

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