High-transmittance soft tpu film and preparation method thereof

Abstract

The present application relates to a kind of high light transmittance soft TPU film and its preparation method, the high light transmittance soft TPU film includes polyurethane nanofiber, polydimethylsiloxane nanofiber and hollow rod-shaped silica nanoparticle, the hollow rod-shaped silica nanoparticle is dispersed in polyurethane nanofiber and polydimethylsiloxane nanofiber.It has the micro network structure of being able to make the light transmittance of film significantly improve, also more soft simultaneously;Polyurethane is used in conjunction with polydimethylsiloxane, and the flexibility of film can be further increased;The hollow rod-shaped silica nanoparticle evenly distributed in fiber is due to its special hollow structure, gives it lower refractive index, makes film have higher light transmittance, also further improves the weather resistance of TPU film, especially temperature resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of synthetic materials, and particularly relates to a TPU film and a preparation method thereof, in particular to a high-transmittance soft TPU film and a preparation method thereof. BACKGROUND

[0002] Polyurethane is a general term for macromolecular compounds containing repeating urethane groups in the main chain, and has excellent wear resistance, oil resistance, tear resistance, chemical corrosion resistance and other properties, and is widely used in various fields. However, how to make TPU have better antibacterial performance has always been a key difficulty, which also limits the application of TPU in a wider range. At the same time, flexible polymer materials with high transmittance have become the focus and hotspot of current film material research and development, but the polyurethane film material in the prior art still has the defect of low transmittance, which limits its application in agriculture or industry.

[0003] CN204020146U discloses a TPU explosion-proof protective film, which is provided with a PET protective layer, a TPU coating layer, an OCA adhesive layer, an optical PET layer, a silica gel layer and a PET fluoroplastic film layer from top to bottom. The TPU explosion-proof protective film disclosed in the present application uses super-transmissive optical PET to effectively improve the light transmittance and clarity of the protective film; and adopts a combination mode of TPU coating layer+OCA adhesive layer to greatly increase the impact buffering capacity of the protective film and prevent screen explosion; the silica gel layer has the ability to automatically adsorb the screen glass, can be applied to screens with a certain curvature, and has the function of quickly exhausting bubbles to ensure the lamination effect of the protective film.

[0004] CN105062041A discloses a TPU film with high transparency and high thermal stability and a preparation method thereof. The TPU film is prepared from the following raw materials by weight parts: 12-18 parts by weight of alicyclic diisocyanate, 7-13 parts by weight of toluene diisocyanate, 35-55 parts by weight of polyester polyol, 6-12 parts by weight of chain extender, 0.2-0.8 parts by weight of defoaming agent, 2-4 parts by weight of ultraviolet absorber, 0.4-1.6 parts by weight of anti-yellowing agent and 0.5-1.5 parts by weight of polytetrafluoroethylene. The preparation method of the TPU film is as follows: first, dry and mix the components according to the formula amount, then extrude through an extruder to prepare the TPU film. The TPU film has high transparency, light transmittance greater than 95%, yellowing resistance grade of 5 or more, and excellent thermal stability and mechanical properties.

[0005] CN104140517A provides a kind of high transparent TPU material of yellowing, mainly including aliphatic or alicyclic diisocyanate, small molecule diol chain extender, amorphous high molecular polyol, linear high molecular polyol etc.Constituent.The TPU material described in the application has the characteristics of high transparency and non-yellowing, and the light transmittance can reach 95%, and the yellowing resistance level can reach 5 levels.At the same time, the application also provides a method for preparing the TPU material, which can be easily prepared by using the method.

[0006] But there are still few strategies in the prior art on how to improve the light transmittance of polyurethane film material, so it is very meaningful to develop a new type of polyurethane film which can keep the light transmittance at a high level and has good flexibility. SUMMARY

[0007] In view of the deficiencies of the prior art, the purpose of the present application is to provide a TPU film and a preparation method thereof, in particular to provide a high-transmittance soft TPU film and a preparation method thereof, which has good softness, good temperature resistance and high light transmittance.

[0008] To achieve the purpose of the present application, the following technical solutions are adopted:

[0009] On the one hand, the present application provides a high-transmittance soft TPU film, which comprises polyurethane nanofiber, polydimethylsiloxane nanofiber and hollow rod-shaped silica nanoparticles, and the hollow rod-shaped silica nanoparticles are dispersed in the polyurethane nanofiber and the polydimethylsiloxane nanofiber.

[0010] The TPU film of the present application is a film with a micro-network structure formed by interweaving polyurethane nanofiber and polydimethylsiloxane nanofiber, which can significantly improve the light transmittance of the film and make it more flexible; polyurethane is a material with good flexibility, and its use with polydimethylsiloxane can further increase the flexibility of the film; the hollow rod-shaped silica nanoparticles uniformly distributed in the polyurethane nanofiber and the polydimethylsiloxane nanofiber have a special hollow structure, which gives them a lower refractive index, so that the film has a higher light transmittance; at the same time, the hollow rod-shaped silica nanoparticles distributed in the fiber also further improve the weather resistance of the TPU film, especially the temperature resistance.

[0011] In the present application, the high light transmittance refers to a light transmittance of 95.5% or more.

[0012] In the present application, the preparation raw materials of the high-transmittance soft TPU film include the following components in parts by weight: diisocyanate 20-40 parts, polyethylene glycol 40-80 parts, chain extender 5-20 parts, polydimethylsiloxane 10-100 parts, and hollow rod-shaped silica nanoparticles 10-30 parts.

[0013] The diisocyanate and polyethylene glycol in the preparation raw materials form a polyurethane material, and the weight ratio of the polydimethylsiloxane and the hollow rod-shaped silica nanoparticles is specially selected. Only under the above weight ratio, the final product can have the best light transmittance, flexibility, and weather resistance.

[0014] The weight of the diisocyanate can be 20 parts, 25 parts, 28 parts, 30 parts, 32 parts, 34 parts, 35 parts, 38 parts, or 40 parts, etc.

[0015] The weight of the polyethylene glycol can be 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, or 80 parts, etc.

[0016] The weight of the chain extender can be 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 16 parts, 17 parts, 18 parts, or 20 parts, etc.

[0017] The weight of the polydimethylsiloxane can be 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, or 100 parts, etc.

[0018] The weight of the hollow rod-shaped silica nanoparticles can be 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 24 parts, 26 parts, 28 parts, or 30 parts, etc.

[0019] Preferably, the diisocyanate includes any one or a combination of at least two of p-phenylene diisocyanate, methylene diisocyanate, or diphenylmethane diisocyanate, such as a combination of p-phenylene diisocyanate and methylene diisocyanate, a combination of methylene diisocyanate and diphenylmethane diisocyanate, a combination of p-phenylene diisocyanate and diphenylmethane diisocyanate, etc.

[0020] Preferably, the number average molecular weight of the polyethylene glycol is 6000-8000, such as 6000, 6200, 6500, 6800, 7000, 7200, 7500, or 8000, etc. The number average molecular weight of the polyethylene glycol determines the length of the soft segment in the polyurethane long chain, which has an important influence on the structural stability and flexibility of the polyurethane nanofiber in the film. Only within the above numerical range, the obtained TPU film can have better flexibility and structural stability.

[0021] Preferably, the chain extender comprises any one or a combination of ethylene glycol, ethylene diamine, 1,3-propanediol, 1,4-butanediol, hexanediol, diethylene glycol or 1,5-pentanediol; the combination of at least two, for example, a combination of ethylene glycol and ethylene diamine, a combination of 1,3-propanediol and 1,4-butanediol, a combination of 1,4-butanediol, hexanediol and diethylene glycol, and the like, other arbitrary combinations are not listed one by one.

[0022] Preferably, the diameter of the hollow rod-shaped silica nanoparticles is 200-500nm, for example, 200nm, 250nm, 300nm, 320nm, 350nm, 400nm, 450nm or 500nm, and the like.

[0023] Preferably, the length of the hollow rod-shaped silica nanoparticles is 500-1000nm, for example, 500nm, 600nm, 700nm, 750nm, 800nm, 900nm or 1000nm, and the like.

[0024] The diameter and length of the hollow rod-shaped silica nanoparticles need to be within the above size range to maintain the light transmittance of the film at an optimal level, and too high or too low will cause the light transmittance to decrease.

[0025] Preferably, the preparation raw material of the high light transmittance soft TPU film further comprises a catalyst 5-10 parts by weight and / or an antioxidant 10-20 parts by weight.

[0026] The weight fraction of the catalyst can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, and the like.

[0027] The weight fraction of the antioxidant can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 18 parts or 20 parts, and the like.

[0028] Preferably, the catalyst comprises any one or a combination of stannous octoate, dibutyltin dioctoate or dibutyltin laurate, the combination of at least two, for example, a combination of stannous octoate and dibutyltin dioctoate, a combination of dibutyltin dioctoate and dibutyltin laurate, a combination of stannous octoate and dibutyltin laurate, and the like, other arbitrary combinations are not listed one by one.

[0029] Preferably, the antioxidant comprises any one or a combination of at least two of a hindered phenolic antioxidant, a hindered amine antioxidant, or a phosphite antioxidant, such as a combination of a hindered phenolic antioxidant and a hindered amine antioxidant, a combination of a hindered amine antioxidant and a phosphite antioxidant, a combination of a hindered phenolic antioxidant and a phosphite antioxidant, and the like, other combinations not being listed here.

[0030] In another aspect, the present application provides a method for preparing the high-transmittance soft TPU film as described above, the method comprising: using electrospinning technology to spin polyurethane nanofibers and polydimethylsiloxane nanofibers respectively, the polyurethane nanofibers and the polydimethylsiloxane nanofibers having hollow rod-shaped silica nanoparticles dispersed therein, and interweaving the polyurethane nanofibers and the polydimethylsiloxane nanofibers to form a film having a network-like microstructure, i.e., the high-transmittance soft TPU film.

[0031] The high-transmittance soft TPU film according to the present application is prepared using electrospinning technology, which is simple and easy to implement and suitable for large-scale industrial production.

[0032] Preferably, the method for preparing the high-transmittance soft TPU film comprises the following steps:

[0033] (1) mixing diisocyanate, polyethylene glycol, a chain extender, a catalyst, and an antioxidant in a certain proportion and then reacting to obtain a polyurethane material;

[0034] (2) mixing the polyurethane material obtained in step (1) with a solvent and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution, and mixing polydimethylsiloxane with a curing agent and hollow rod-shaped silica nanoparticles to obtain a polydimethylsiloxane composite solution;

[0035] (3) independently loading the polyurethane composite solution and the polydimethylsiloxane composite solution obtained in step (2) into a sample, and using a multi-nozzle electrospinning device to perform electrospinning, so that the polyurethane composite solution and the polydimethylsiloxane composite solution are interwoven to form the high-transmittance soft TPU film.

[0036] In the present application, the reaction in step (1) is performed under stirring.

[0037] Preferably, the stirring rate is 1000-2000 r / min, such as 1000 r / min, 1200 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1800 r / min, or 2000 r / min, and the like.

[0038] Preferably, the reaction in step (1) is performed under vacuum dehydration.

[0039] Preferably, the temperature of the reaction in step (1) is 100-120℃, such as 100℃, 102℃, 105℃, 108℃, 110℃, 112℃, 115℃, 118℃ or 120℃, etc.

[0040] Preferably, the time of the reaction in step (1) is 10-24h, such as 10h, 12h, 15h, 16h, 18h, 20h, 22h, 23h or 24h, etc.

[0041] In the above-mentioned synthesis reaction of polyurethane, the temperature and time of the reaction are selected in the above-mentioned numerical ranges, so that the reaction is more sufficient, which has an important influence on the structural stability of the subsequent formation of polyurethane nanofiber.

[0042] In the present application, the solvent in step (2) includes any one or a combination of at least two of N,N-dimethylformamide, acetone or hexafluoroisopropanol, such as a combination of N,N-dimethylformamide and acetone, a combination of acetone and hexafluoroisopropanol, a combination of N,N-dimethylformamide and hexafluoroisopropanol, etc., and other arbitrary combination modes are not described one by one here.

[0043] Preferably, the mass concentration of the polyurethane composite solution in step (2) is 30-50%, such as 30%, 32%, 35%, 38%, 40%, 42%, 45% or 50%, etc.

[0044] The mass concentration of the polyurethane composite solution is specifically selected in the range of 30-50%, because under this concentration range, the pore size of the polyurethane nanofiber network structure formed by spinning can ensure high light transmittance and also make the film structure have good stability.

[0045] Preferably, the curing agent in step (2) includes any one or a combination of at least two of vinyl triamine, aminoethyl piperazine, diaminocyclohexane, diethylene triamine or triethylene tetramine, such as a combination of vinyl triamine and aminoethyl piperazine, a combination of diaminocyclohexane and diethylene triamine, a combination of diethylene triamine and triethylene tetramine, etc., and other arbitrary combination modes are not described one by one here.

[0046] Preferably, the preparation method of the hollow rod-shaped silica nanoparticles in step (2) includes the following steps:

[0047] (I) Synthesis of rod-shaped mesoporous silica nanoparticles:

[0048] Weigh out hexadecyltrimethylammonium bromide (CTAB), dissolve it in water, and place it in an ultrasonic cleaner to sonicate until completely dissolved. After sonication, add ammonia water, stir magnetically to mix completely, and add tetraethyl orthosilicate (TEOS) dropwise while stirring. React in a constant temperature water bath at 40°C for 2 hours while stirring, centrifuge, and wash for later use.

[0049] (II) The rod-shaped mesoporous silica nanoparticles prepared in step (I) are mixed and reacted with tetraethyl orthosilicate to obtain bilayer silica:

[0050] The prepared rod-shaped mesoporous silica was dispersed in an aqueous ethanol solution and sonicated to ensure complete dispersion. Ammonia was added under magnetic stirring. Then, TEOS was added dropwise in a 40°C constant temperature water bath with vigorous stirring, and the reaction was carried out for 6 hours with vigorous stirring. After the reaction was complete, the silica was centrifuged and washed several times with water and ethanol before use.

[0051] (III) The bilayer silica prepared in step (II) is mixed and reacted with polyvinylpyrrolidone to obtain polyvinylpyrrolidone-coated bilayer silica:

[0052] The prepared bilayer silica was dispersed in water, sonicated, and then polyvinylpyrrolidone (PVP) was added. Sonication was continued until complete dispersion. The mixture was then refluxed at 100°C for 3 hours and centrifuged for later use.

[0053] (IV) The polyvinylpyrrolidone-coated bilayer silica prepared in step (III) is mixed with sodium carbonate solution for etching, and then dried to obtain the hollow rod-shaped silica nanoparticles:

[0054] The PVP-coated bilayer silica prepared above was dispersed in water and ultrasonicated to ensure complete dispersion. Then, a 0.3M sodium carbonate solution was added, and the mixture was etched for 2 hours under magnetic stirring. The resulting product was centrifuged, washed repeatedly with water, dried, and calcined to obtain the hollow rod-shaped silica nanoparticles.

[0055] In this invention, the inner diameter of the nozzle of the electrospinning in step (3) is 0.4-0.6 mm, for example, 0.4 mm, 0.5 mm or 0.6 mm.

[0056] Preferably, the voltage of electrospinning in step (3) is 12-16kV, such as 12kV, 13kV, 14kV, 15kV or 16kV.

[0057] Preferably, the distance between the needle tip and the current collector in step (3) is 12-16cm, such as 12cm, 13cm, 14cm, 15cm or 16cm.

[0058] Preferably, the temperature during electrospinning is 20-30℃, such as 20℃, 22℃, 24℃, 25℃, 26℃, 28℃, 29℃ or 30℃.

[0059] Preferably, the liquid feed rate of the electrospinning in step (3) is 0.5-1.0 mL / L, such as 0.5 mL / L, 0.6 mL / L, 0.7 mL / L, 0.8 mL / L, 0.9 mL / L or 1.0 mL / L.

[0060] The aforementioned limitations on the series of parameters during electrospinning enable the final product to achieve the aforementioned beneficial effects.

[0061] Preferably, after obtaining the nano-antibacterial and breathable TPU film in step (3), the post-treatment is further included. The post-treatment operation is to vacuum dry the nano-antibacterial and breathable TPU film at 20-30℃ (e.g., 20℃, 22℃, 25℃, 27℃ or 30℃, etc.) for 24-72h (e.g., 24h, 30h, 40h, 50h, 60h or 72h, etc.).

[0062] As a preferred embodiment of the present invention, the preparation method specifically includes the following steps:

[0063] (1) After mixing diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant in proportion, the reaction is carried out under vacuum dehydration conditions and at 100-120℃ with stirring at a rate of 1000-2000r / min for 10-24h to obtain polyurethane material.

[0064] (2) The polyurethane material obtained in step (1) is mixed with solvent and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution with a mass concentration of 30-50%; polydimethylsiloxane is mixed with curing agent and hollow rod-shaped silica nanoparticles to obtain a polydimethylsiloxane composite solution.

[0065] (3) The polyurethane composite solution and polydimethylsiloxane composite solution obtained in step (2) are separately loaded into samples and electrospun using a multi-nozzle electrospinning device to interweave them to form the high-transmittance soft TPU film; the inner diameter of the nozzle is 0.4-0.6 mm; the voltage is 12-16 kV; the distance between the needle tip and the collector is 12-16 cm; the temperature is 20-30 ℃; and the liquid injection rate is 0.5-1.0 mL / L.

[0066] (4) The high-transmittance soft TPU film obtained in step (3) is vacuum dried at 20-30℃ for 24-72h.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] The TPU film involved in this invention has a light transmittance of 95.5% or higher. It is a film with a micro-network structure formed by interwoven polyurethane nanofibers and polydimethylsiloxane nanofibers. This micro-network structure can significantly improve the light transmittance of the film and also make it more flexible. Polyurethane itself is a flexible material, and its combination with polydimethylsiloxane can further increase the flexibility of the film. The hollow rod-shaped silica nanoparticles uniformly distributed in the polyurethane nanofibers and polydimethylsiloxane nanofibers have a lower refractive index due to their special hollow structure, thus giving the film higher light transmittance. At the same time, the hollow rod-shaped silica nanoparticles distributed in the fibers also further improve the weather resistance of the TPU film, especially its temperature resistance. Detailed Implementation

[0069] To further illustrate the technical means and effects of the present invention, the following describes the technical solution of the present invention in conjunction with preferred embodiments of the present invention. However, the present invention is not limited to the scope of the embodiments.

[0070] Example 1

[0071] This embodiment provides a high-transmittance flexible TPU film, which comprises polyurethane nanofibers, polydimethylsiloxane nanofibers, and hollow rod-shaped silica nanoparticles. The hollow rod-shaped silica nanoparticles are dispersed in the polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials for its preparation are: 30 parts terephthalic acid diisocyanate, 60 parts polyethylene glycol (PEG6000), 10 parts chain extender (a mixture of 1,4-butanediol, hexanediol, and diethylene glycol in a mass ratio of 1:1:1), 5 parts catalyst (stannous octoate), 10 parts antioxidant (CHEMNOX 1010), 50 parts polydimethylsiloxane (viscosity (25℃ cp) of 10000), and 20 parts hollow rod-shaped silica nanoparticles. The preparation method is as follows:

[0072] (1) After mixing terephthalic diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant in proportion, the mixture was stirred at 1500 r / min for 15 h under vacuum dehydration conditions and at 110 °C to obtain polyurethane material.

[0073] (2) The polyurethane material obtained in step (1) is mixed with N,N-dimethylformamide and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution with a mass concentration of 40%; polydimethylsiloxane is mixed with vinyltriamine (the mass ratio of polydimethylsiloxane to curing agent is 1:2) and hollow rod-shaped silica nanoparticles to obtain a polydimethylsiloxane composite solution;

[0074] (3) The polyurethane composite solution and polydimethylsiloxane composite solution obtained in step (2) are separately loaded into samples and electrospun using a multi-nozzle electrospinning device to interweave them to form the high-transmittance soft TPU film; the nozzle inner diameter is 0.5 mm; the voltage is 14 kV; the distance between the needle tip and the collector is 14 cm; the temperature is 25 °C; and the liquid injection rate is 0.8 mL / L.

[0075] (4) The high transmittance soft TPU film obtained in step (3) is vacuum dried at 25°C for 48 hours.

[0076] Example 2

[0077] This embodiment provides a high-transmittance flexible TPU film, which comprises polyurethane nanofibers, polydimethylsiloxane nanofibers, and hollow rod-shaped silica nanoparticles. The hollow rod-shaped silica nanoparticles are dispersed in the polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials for its preparation are: 20 parts methylene diisocyanate, 40 parts polyethylene glycol (PEG8000), 5 parts chain extender (ethylenediamine), 10 parts catalyst (dibutyltin dioctanoate), 20 parts antioxidant (CHEMNOX1076), 10 parts polydimethylsiloxane (viscosity (25℃ cp) 50000), and 10 parts hollow rod-shaped silica nanoparticles. The preparation method is as follows:

[0078] (1) Methylene diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant are mixed in proportion and reacted. The reaction is carried out under vacuum dehydration conditions and at 100°C with stirring at a rate of 1000 r / min for 24 h to obtain polyurethane material.

[0079] (2) The polyurethane material obtained in step (1) is mixed with N,N-dimethylformamide and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution with a mass concentration of 50%; polydimethylsiloxane is mixed with diaminocyclohexane (the mass ratio of polydimethylsiloxane to curing agent is 1:2) and hollow rod-shaped silica nanoparticles to obtain a polydimethylsiloxane composite solution.

[0080] (3) The polyurethane composite solution and polydimethylsiloxane composite solution obtained in step (2) are separately loaded into samples and electrospun using a multi-nozzle electrospinning device to interweave them to form the high-transmittance soft TPU film; the inner diameter of the nozzle is 0.4 mm; the voltage is 16 kV; the distance between the needle tip and the collector is 12 cm; the temperature is 30 ℃; the liquid injection rate is 0.5 mL / L;

[0081] (4) The high light transmittance soft TPU film obtained in step (3) is vacuum dried at 20°C for 72 hours.

[0082] Example 3

[0083] This embodiment provides a high-transmittance flexible TPU film, which comprises polyurethane nanofibers, polydimethylsiloxane nanofibers, and hollow rod-shaped silica nanoparticles. The hollow rod-shaped silica nanoparticles are dispersed in the polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials for its preparation are: 40 parts diphenylmethane diisocyanate, 80 parts polyethylene glycol (PEG6000), 20 parts chain extender (diethylene glycol), 5 parts catalyst (dibutyltin laurylate), 10 parts antioxidant (CHEMNOX168), 100 parts polydimethylsiloxane (viscosity (25℃ cp) 20000), and 30 parts hollow rod-shaped silica nanoparticles. The preparation method is as follows:

[0084] (1) Diphenylmethane diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant are mixed in proportion and reacted. The reaction is carried out under vacuum dehydration conditions and at 120°C with stirring at a rate of 2000 r / min for 10 h to obtain polyurethane material.

[0085] (2) The polyurethane material obtained in step (1) is mixed with acetone and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution with a mass concentration of 30%; polydimethylsiloxane is mixed with diethylenetriamine (the mass ratio of polydimethylsiloxane to curing agent is 1:2) and hollow rod-shaped silica nanoparticles to obtain a polydimethylsiloxane composite solution.

[0086] (3) The polyurethane composite solution and polydimethylsiloxane composite solution obtained in step (2) are separately loaded into samples and electrospun using a multi-nozzle electrospinning device to interweave them to form the high-transmittance soft TPU film; the nozzle inner diameter is 0.6 mm; the voltage is 12 kV; the distance between the needle tip and the collector is 16 cm; the temperature is 20 °C; and the liquid injection rate is 1.0 mL / L.

[0087] (4) The high transmittance soft TPU film obtained in step (3) is vacuum dried at 30°C for 24 hours.

[0088] Example 4

[0089] This embodiment provides a high-transmittance flexible TPU film, which comprises polyurethane nanofibers, polydimethylsiloxane nanofibers, and hollow rod-shaped silica nanoparticles. The hollow rod-shaped silica nanoparticles are dispersed within the polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials are the same as in Example 1, except that "20 parts of hollow rod-shaped silica nanoparticles" are changed to "50 parts of hollow rod-shaped silica nanoparticles," while all other conditions remain unchanged. The preparation method is also consistent with Example 1.

[0090] Example 5

[0091] This embodiment provides a high-transmittance flexible TPU film, which comprises polyurethane nanofibers, polydimethylsiloxane nanofibers, and hollow rod-shaped silica nanoparticles. The hollow rod-shaped silica nanoparticles are dispersed within the polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials are the same as in Example 1, except that "20 parts of hollow rod-shaped silica nanoparticles" are changed to "5 parts of hollow rod-shaped silica nanoparticles," while all other conditions remain unchanged. The preparation method is also consistent with Example 1.

[0092] Example 6

[0093] This embodiment provides a high-transmittance flexible TPU film, which comprises polyurethane nanofibers, polydimethylsiloxane nanofibers, and hollow rod-shaped silica nanoparticles. The hollow rod-shaped silica nanoparticles are dispersed in the polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials are the same as in Example 1. The only difference between the preparation method and Example 1 is that "the concentration of the polyurethane composite solution in step (2) is 20%", all other aspects are the same.

[0094] Example 7

[0095] This embodiment provides a high-transmittance flexible TPU film, which comprises polyurethane nanofibers, polydimethylsiloxane nanofibers, and hollow rod-shaped silica nanoparticles. The hollow rod-shaped silica nanoparticles are dispersed in the polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials are the same as in Example 1. The only difference between this preparation method and Example 1 is that "the concentration of the polyurethane composite solution in step (2) is 60%", all other aspects are the same.

[0096] Comparative Example 1

[0097] This embodiment provides a TPU film comprising polyurethane nanofibers and hollow rod-shaped silica nanoparticles, wherein the hollow rod-shaped silica nanoparticles are dispersed within the polyurethane nanofibers. The raw materials for its preparation are: 30 parts diisocyanate, 60 parts polyethylene glycol (PEG6000), 10 parts chain extender (a mixture of 1,4-butanediol, hexanediol, and diethylene glycol in a mass ratio of 1:1:1), 5 parts catalyst (stannous octoate), 10 parts antioxidant (CHEMNOX 1010), and 20 parts hollow rod-shaped silica nanoparticles.

[0098] Its preparation method is as follows:

[0099] (1) Diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant are mixed in proportion and reacted. The reaction is carried out under vacuum dehydration conditions and at 110°C with stirring at a rate of 1500 r / min for 15 h to obtain polyurethane material.

[0100] (2) The polyurethane material obtained in step (1) is mixed with N,N-dimethylformamide and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution with a mass concentration of 40%.

[0101] (3) The polyurethane composite solution obtained in step (2) is electrospun using a multi-nozzle electrospinning device to interweave and form the high-transmittance soft TPU film; the nozzle inner diameter is 0.5 mm; the voltage is 14 kV; the distance between the needle tip and the collector is 14 cm; the temperature is 25 °C; and the liquid inlet rate is 0.8 mL / L.

[0102] (4) The TPU film obtained in step (3) is vacuum dried at 25°C for 48 hours.

[0103] Comparative Example 2

[0104] This embodiment provides a TPU film comprising polyurethane nanofibers and polydimethylsiloxane nanofibers. The raw materials for its preparation are: 30 parts diisocyanate, 60 parts polyethylene glycol (PEG6000), 10 parts chain extender (a mixture of 1,4-butanediol, hexanediol, and diethylene glycol in a mass ratio of 1:1:1), 5 parts catalyst (stannous octoate), 10 parts antioxidant (CHEMNOX 1010), and 50 parts polydimethylsiloxane (viscosity (25℃ cp) of 10000). The preparation method is as follows:

[0105] (1) Diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant are mixed in proportion and reacted. The reaction is carried out under vacuum dehydration conditions and at 110°C with stirring at a rate of 1500 r / min for 15 h to obtain polyurethane material.

[0106] (2) Mix the polyurethane material obtained in step (1) with N,N-dimethylformamide to obtain a polyurethane composite solution with a mass concentration of 40%; mix polydimethylsiloxane with vinyltriamine (the mass ratio of polydimethylsiloxane to curing agent is 1:2) to obtain a polydimethylsiloxane composite solution.

[0107] (3) The polyurethane composite solution and polydimethylsiloxane composite solution obtained in step (2) are separately loaded into samples and electrospun using a multi-nozzle electrospinning device to interweave them to form the high-transmittance soft TPU film; the nozzle inner diameter is 0.5 mm; the voltage is 14 kV; the distance between the needle tip and the collector is 14 cm; the temperature is 25 °C; and the liquid injection rate is 0.8 mL / L.

[0108] (4) The TPU film obtained in step (3) is vacuum dried at 25°C for 48 hours.

[0109] Comparative Example 3

[0110] This embodiment provides a TPU film, the raw materials for which are prepared being completely identical to those in Example 1. The preparation method is as follows:

[0111] (1) Diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant are mixed in proportion and reacted. The reaction is carried out under vacuum dehydration conditions and at 110°C with stirring at a rate of 1500 r / min for 15 h to obtain polyurethane material.

[0112] (2) The polyurethane material obtained in step (1) is mixed with polydimethylsiloxane and vinyltriamine (the mass ratio of polydimethylsiloxane to curing agent is 1:2), and the mixture is obtained after curing.

[0113] (3) The mixture obtained in step (2) is extruded using a twin-screw extruder to obtain the TPU film;

[0114] (4) The TPU film obtained in step (3) is vacuum dried at 25°C for 48 hours.

[0115] Evaluation test:

[0116] The light transmittance and flexibility of the TPU films prepared in Examples 1-7 and Comparative Examples 1-3 were evaluated, including the following tests:

[0117] (1) Transmittance test: The transmittance test standard GB / T 2410-2008 was used, and the results are shown in Table 1;

[0118] (2) Tensile strength test: The tensile strength test method GB / T 528-2009 was used, and the results are shown in Table 1;

[0119] Table 1

[0120] Transmittance Tensile strength (MPa) Example 1 99.2％ 37 Example 2 99.1％ 35 Example 3 99.4％ 35 Example 4 99.2％ 30 Example 5 95.5％ 39 Example 6 99.5％ 31 Example 7 96.4％ 37 Comparative Example 1 98.2％ 26 Comparative Example 2 91.8％ 36 Comparative Example 3 93.1％ 28

[0121] As shown in Table 1, the TPU film of this invention exhibits excellent light transmittance and flexibility, with a light transmittance exceeding 95.5% and a tensile strength exceeding 30 MPa. Comparing Examples 1, 4, and 5, the weight fraction of hollow rod-shaped silica nanoparticles significantly affects the light transmittance and flexibility of the film; an excessively high weight fraction slightly reduces flexibility, while an excessively low weight fraction slightly reduces light transmittance. Comparing Examples 1, 6, and 7, the concentration of the polyurethane composite solution significantly affects the light transmittance and flexibility of the film; an excessively high concentration slightly reduces light transmittance, while an excessively low concentration slightly reduces flexibility. The data from Comparative Examples 1-3 indicate that the absence of hollow rod-shaped silica nanoparticles or polydimethylsiloxane significantly reduces the light transmittance or tensile strength of the TPU film.

[0122] The applicant declares that this invention illustrates a high-transmittance flexible TPU film and its preparation method through the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials of this invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

[0123] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0124] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A high light transmission flexible TPU film characterized in that, The high-transmittance soft TPU film comprises polyurethane nanofibers, polydimethylsiloxane nanofibers and hollow rod-shaped silica nanoparticles dispersed in the polyurethane nanofibers and the polydimethylsiloxane nanofibers. The preparation raw materials of the high-transmittance soft TPU film comprise the following components in parts by weight: 20-40 parts of diisocyanate, 40-80 parts of polyethylene glycol, 5-20 parts of chain extender, 10-100 parts of polydimethylsiloxane, 10-30 parts of hollow rod-shaped silica nanoparticles, 5-10 parts of catalyst and 10-20 parts of antioxidant. The high-transmittance soft TPU film has a transmittance of 95.5% or above. The high-transmittance soft TPU film is prepared by the following method, which comprises the following steps: (1) mixing diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant in a certain proportion and then reacting, stirring at a speed of 1000-2000 r / min under vacuum dehydration conditions and at 100-120℃ for 10-24 h to obtain a polyurethane material; (2) mixing the polyurethane material obtained in step (1) with a solvent and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution with a mass concentration of 30-50%; mixing polydimethylsiloxane with a curing agent and hollow rod-shaped silica nanoparticles to obtain a polydimethylsiloxane composite solution; (3) independently loading the polyurethane composite solution and the polydimethylsiloxane composite solution obtained in step (2) into a multi-nozzle electrospinning device to perform electrospinning so as to interweave them to form the high-transmittance soft TPU film; the inner diameter of the nozzle is 0.4-0.6 mm; the voltage is 12-16 kV; the distance between the needle tip and the collecting electrode is 12-16 cm; the temperature is 20-30℃; and the liquid feeding speed is 0.5-1.0 mL / L; (4) vacuum drying the high-transmittance soft TPU film obtained in step (3) at 20-30℃ for 24-72 h.

2. The high transmission flexible TPU film according to claim 1, wherein, The diisocyanate comprises any one or a combination of at least two of p-phenylene diisocyanate, methylene diisocyanate or diphenylmethane diisocyanate.

3. The high transmission flexible TPU film according to claim 1, wherein, The number average molecular weight of the polyethylene glycol is 6000-8000.

4. The high transmission flexible TPU film according to claim 1, wherein, The chain extender comprises any one or a combination of at least two of ethylene glycol, ethylenediamine, 1,3-propanediol, 1,4-butanediol, hexanediol, diethylene glycol or 1,5-pentanediol.

5. The high transmission flexible TPU film according to claim 4, wherein, The chain extender comprises a combination of 1,4-butanediol, hexanediol and diethylene glycol.

6. The high transmission flexible TPU film according to claim 1, wherein, The hollow rod-shaped silica nanoparticles have a diameter of 200-500 nm.

7. The high transmission flexible TPU film according to claim 1, wherein, The hollow rod-shaped silica nanoparticles have a length of 500-1000 nm.

8. The high transmission flexible TPU film according to claim 1, wherein, The catalyst comprises any one or a combination of at least two of stannous octoate, dibutyltin dioctoate or dibutyltin laurate.

9. The high transmission flexible TPU film according to claim 1, wherein, The antioxidant comprises any one or a combination of at least two of hindered phenolic antioxidant, hindered amine antioxidant or phosphite antioxidant.

10. The method for preparing a high-transmittance flexible TPU film according to any one of claims 1-9, characterized in that, The preparation method comprises the following steps: (1) mixing diisocyanate, polyethylene glycol, chain extender, catalyst and antioxidant in proportion and then reacting to obtain polyurethane material; (2) mixing the polyurethane material obtained in step (1) with solvent and hollow rod-shaped silica nanoparticles to obtain a polyurethane composite solution with a mass concentration of 30-50%; mixing polydimethylsiloxane with curing agent and hollow rod-shaped silica nanoparticles to obtain a polydimethylsiloxane composite solution; (3) independently loading the polyurethane composite solution and the polydimethylsiloxane composite solution obtained in step (2) into a multi-nozzle electrospinning device to perform electrospinning to interweave them to form the high-transmittance soft TPU film.

11. The method for preparing a high-transmittance flexible TPU film as described in claim 10, characterized in that, The solvent in step (2) includes any one or a combination of at least two of N,N-dimethylformamide, acetone or hexafluoroisopropanol.

12. The method for preparing a high-transmittance flexible TPU film as described in claim 10, characterized in that, The curing agent in step (2) includes any one or a combination of at least two of vinyl triamine, aminoethyl piperazine, diaminocyclohexane, diethylene triamine or triethylene tetramine.

13. The method for preparing a high-transmittance flexible TPU film as described in claim 10, characterized in that, The preparation method of the hollow rod-shaped silica nanoparticles in step (2) includes the following steps: (I) synthesizing rod-shaped mesoporous silica nanoparticles; (II) mixing the rod-shaped mesoporous silica nanoparticles prepared in step (I) with tetraethyl orthosilicate to obtain double-layered silica; (III) mixing the double-layered silica prepared in step (II) with polyvinylpyrrolidone to obtain double-layered silica coated with polyvinylpyrrolidone; (IV) mixing the double-layered silica coated with polyvinylpyrrolidone prepared in step (III) with sodium carbonate solution to perform etching, and then drying to obtain the hollow rod-shaped silica nanoparticles.