A composite nucleating agent for TPU film, a TPU film and a preparation method

Abstract

The present invention belongs to the technical field of TPU polymer materials, and specifically relates to a composite nucleating agent for TPU film, a TPU film and a preparation method. The composite nucleating agent is prepared by chelating an organic nucleating agent and an antioxidant with a specific inorganic nanopowder modified by silane under high temperature and high pressure. The composite nucleating agent and TPU resin are pre-dispersed after granulation by a twin-screw extruder to obtain a composite nucleating agent masterbatch. The TPU film is made by mixing the composite nucleating agent masterbatch and TPU resin particles and then extruding and casting. The composite nucleating agent of the present invention can accelerate the molding efficiency of the TPU film, improve the light transmittance of the TPU film, has no precipitation under high temperature and high humidity conditions, and helps to enhance the mechanical properties of the TPU film. This will greatly improve the production efficiency of the TPU film and also inspire the development of other high-performance elastomeric materials.

Description

Technical Field

[0001] The invention belongs to the technical field of TPU polymer materials, and specifically relates to a composite nucleating agent for a TPU film, a TPU film and a preparation method. Background Art

[0002] TPU polymer is a commonly used thermoplastic polyurethane material. The film made from it has the advantages of high strength, high toughness, high wear resistance, low temperature resistance, environmental protection, non-toxicity, and biodegradability. It is widely used in high-end fields such as clothing fabrics, national defense and military industry, medical care, aerospace, and artificial intelligence.

[0003] However, on the one hand, TPU has a low crystallization temperature and a slow crystallization rate. After being stretched, the TPU film still has internal stress, and the molecular chain has a certain retraction. After being wound, the TPU film is prone to curling, which causes wrinkles on the surface of the product and poor opening performance of the film after winding. On the other hand, specific fields (such as packaging bags, medical devices, etc.) have higher requirements for the light transmittance of TPU. TPU material is a block polymer formed by alternating flexible soft segments and rigid hard segments. The thermodynamic incompatibility of the soft and hard segments produces microphase separation, which then changes to macrophase separation, resulting in the TPU film being white or light yellow hazy, or even completely opaque.

[0004] Nucleating agents are an important class of polymer processing aids. They promote heterogeneous nucleation and crystallization of resins, shorten product molding cycles, and improve product processing and application performance. Current nucleating agents are generally divided into inorganic nucleating agents, organic nucleating agents, and polymer nucleating agents. Among them, inorganic nucleating agents have poor transparency and surface gloss, which limits their application; organic nucleating agents include fatty carboxylic acid metal compounds, sorbitol benzyl derivatives, aromatic carboxylic acid metal compounds, organic phosphates and wood acid and its derivatives, sodium benzoate and bis (p-tert-butylbenzoic acid) carboxyl aluminum, rosin nucleating agents, etc. Among them, sorbitol benzyl derivatives are a kind of transparent nucleating agent, which has a significant improvement effect on the transparency, surface gloss, rigidity and other thermodynamic properties of the product. In addition, new polymer transparent nucleating agents for TPU materials are also being developed. For example, patent documents CN112920368A and CN115216138A respectively provide two new nucleating agent products, which are conducive to improving light transmission performance.

[0005] Due to the change of thermodynamic behavior, the addition of nucleating agent will affect the processing and mechanical properties of TPU materials, such as strength, aperture ratio, etc., and also affect the light transmittance of TPU materials, such as light transmittance, haze, etc. Therefore, it is necessary to select nucleating agent according to the performance requirements of TPU materials. However, it is difficult for existing nucleating agents to meet the multiple performance requirements of TPU materials at the same time, which is related to complex factors such as heterogeneous crystallization behavior, crystallization uniformity, and material compatibility after the addition of nucleating agent.

[0006] Patent document CN112920367A provides a BI-SiO2 / TPU to improve the light transmittance of the material, but this is still an isocyanate material compatible with TPU and has been used for the modification of TPU. Patent document CN105820444A provides a polypropylene material, which uses surface-modified calcium sulfate crystals and organic nucleating agents to make an emulsion as a nucleating agent to improve the light transmittance of the polypropylene material. However, the structures of polypropylene and TPU materials and the reasons for the reduction of light transmittance are different, and the document does not fully consider the influence of the difference in optical refractive index between the nucleating agent and the polymer resin on the light transmittance of the product, nor does it mention the powder precipitation behavior caused by the difference in compatibility between the powder and the polymer resin. Unlike polypropylene materials, TPU is a block polymer with a microphase separation structure. Directly filling a nucleating agent that is not selected according to the inherent optical refractive index of TPU will cause the TPU film to be atomized and the transparency to decrease. In addition, ordinary organic nucleating agents have a low molecular weight and are very easy to precipitate from the inside of the film, affecting the appearance and subsequent use of the product.

[0007] In order to meet the increasing market demand, especially the comprehensive requirements for the mechanical properties of TPU materials, improving curling and wrinkling problems, and increasing light transmittance, while taking into account the needs of material cost control, it is necessary to develop nucleating agents for TPU and new TPU film materials. Summary of the invention

[0008] In view of the above technical problems, the purpose of the present invention is to provide a composite nucleating agent for TPU film, a TPU film and a preparation method.

[0009] First, the present invention provides a composite nucleating agent for TPU film, which can accelerate the molding efficiency of TPU film, improve the light transmittance of TPU film, have no precipitation under high temperature and high humidity conditions, and help to enhance the mechanical properties of TPU film, which will greatly improve the production efficiency of TPU film. The specific scheme is as follows:

[0010] A composite nucleating agent for TPU film is made of modified inorganic nano powder, antioxidant and organic nucleating agent, and its preparation method comprises the following steps:

[0011] S1 Preparation of modified inorganic nanopowder: dispersing an inorganic nanopowder nucleating agent in a methanol-water mixed solution, adding a silane coupling agent, reacting at a pH value of 9 to 10 and 70° C. to 100° C., and after the reaction is completed, drying the precipitate to obtain a modified inorganic nanopowder;

[0012] S2 Preparation of composite nucleating agent: Take the modified inorganic nanopowder obtained in step S1, add antioxidant, heat to 50℃~150℃, add organic nucleating agent, react under 0.5Mpa~4.0Mpa, after the reaction is completed, grind the mixture, sieve to obtain composite nucleating agent.

[0013] Preferably, in step S1, the weight ratio of the inorganic nanopowder nucleating agent to the silane coupling agent is (10-35):(1-5); further preferably, in step S1, the weight ratio of the inorganic nanopowder nucleating agent to the silane coupling agent is (15-30):(1-2.5).

[0014] Preferably, in the step S2, the weight ratio of the modified inorganic nanopowder, antioxidant and organic nucleating agent is (100~350):(0.1~0.5):(10~200); further preferably, in the step S2, the weight ratio of the modified inorganic nanopowder, antioxidant and organic nucleating agent is (140~300):(0.1~0.4):(20~150); further preferably, in the step S2, the weight ratio of the modified inorganic nanopowder, antioxidant and organic nucleating agent is (150~280):(0.1~0.3):(20~80).

[0015] Preferably, in step S1, the average particle size of the inorganic nano powder nucleating agent is 20nm~500nm; further preferably, the average particle size of the inorganic nano powder nucleating agent is 100nm~200nm. Still further preferably, the average particle size of the inorganic nano powder nucleating agent is 140nm~200nm. Within the particle size range of nanometer level, for those of ordinary skill in the art, a smaller particle size is conducive to reducing the particle size of heterogeneous nucleation, thereby improving light transmittance, which is known to those of ordinary skill in the art. Therefore, the average particle size of the inorganic nano powder can be selected by those of ordinary skill in the art according to the characteristics of the material.

[0016] Preferably, in step S1, the inorganic nanopowder nucleating agent may be an inorganic nanopowder having an optical refractive index of 1.35 to 1.55, for example, one or more of silicon dioxide, hydrotalcite, glass microspheres, sodium silicate, and mica powder may be selected.

[0017] Preferably, in step S1, the methanol-water mixed solution is made of methanol and water in a volume ratio of 1: (0.1-1.2). Further preferably, in step S1, the methanol-water mixed solution is made of methanol and water in a volume ratio of 1: (0.1-0.2). Since the methanol-water mixed solution is only used as a liquid solvent for the reaction, its ratio can be selected by ordinary technicians in this field according to the reaction raw materials.

[0018] Preferably, in step S1, the reaction temperature is 80°C to 100°C.

[0019] Preferably, in step S1, the reaction time is 3 h to 7 h. Further preferably, in step S1, the reaction time is 3 h to 5 h.

[0020] Preferably, in step S1, the silane coupling agent is selected from at least one of γ-(ethylenediamino)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, anilinomethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane and vinyltri(2-methoxyethoxy)silane.

[0021] Preferably, in step S2, the antioxidant is a composite antioxidant composed of a hindered phenol antioxidant and a phosphite antioxidant. The weight ratio of the hindered phenol antioxidant to the phosphite antioxidant in the composite antioxidant is (1-3): (1-5). Further preferably, the weight ratio of the hindered phenol antioxidant to the phosphite antioxidant in the composite antioxidant is (1-2): (1-4). The hindered phenol antioxidant and the phosphite antioxidant have good synergistic antioxidant properties. Further preferably, the hindered phenol antioxidant is selected from at least one of antioxidant 1010 and antioxidant 1076, and the phosphite antioxidant is selected from at least one of antioxidant 168, antioxidant 618, and antioxidant 608. Finished products of this type of composite antioxidants are already on sale, such as antioxidant 215 (composed of hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a ratio of 1:2 by mass), antioxidant 225 (composed of hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a ratio of 1:1 by mass), antioxidant 220 (composed of hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a ratio of 1:3 by mass), and antioxidant 561 (composed of hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a ratio of 1:4 by mass), which can be purchased on the market.

[0022] Preferably, in step S2, the organic nucleating agent is a carboxylic acid metal salt nucleating agent, a phosphate metal salt nucleating agent, a sorbitol benzyl derivative nucleating agent, an aromatic two At least one of the amide nucleating agents. For example, di[2,2-methylene-di(4,6-di-tert-butylphenyl)carboxylic acid]hydroxyaluminum and sodium β-naphthoate in carboxylic acid metal salt nucleating agents; sodium 2,2-methylene-di(4,6-di-tert-butylphenyl)phosphate in phosphate metal salt nucleating agents; di-(p-methylbenzylidene) sorbitol in sorbitol benzyl derivative nucleating agents; N,N-dicyclohexylterephthalamide in aromatic diamide nucleating agents.

[0023] Preferably, in step S2, the temperature is raised to 100°C to 150°C, an organic nucleating agent is added, and the reaction is carried out at 0.5Mpa to 2.0Mpa for 8 to 30 hours. Further preferably, in step S2, the temperature is raised to 100°C to 120°C, an organic nucleating agent is added, and the reaction is carried out at 0.8Mpa to 1.5Mpa for 10 to 24 hours.

[0024] Secondly, the present invention provides a TPU film, specifically a high light transmittance TPU film with fast molding, few wrinkles, good flattening effect, and high strength. The TPU film is made of film-grade polyester TPU resin particles and the composite nucleating agent, and the content of the composite nucleating agent in the TPU film is 2.6‰~3.0‰ (weight ratio).

[0025] Preferably, the content of the composite nucleating agent in the TPU film is 2.7‰~2.8‰ (weight ratio).

[0026] Again, the present invention provides a method for preparing the aforementioned TPU film, and the preparation method comprises the following steps: T1 preparation of composite nucleating agent-TPU mixed masterbatch: taking film-grade polyester TPU resin particles and composite nucleating agent, adding them into a twin-screw extruder for granulation to prepare composite nucleating agent-TPU mixed masterbatch.

[0027] Preferably, the preparation method further comprises the following steps: T2 TPU film preparation: taking the composite nucleating agent-TPU mixed masterbatch obtained in step T1 and adding film-grade polyester TPU resin particles, and preparing the TPU film by extrusion casting method.

[0028] Preferably, in step T1, the content of the composite nucleating agent in the composite nucleating agent-TPU mixed masterbatch is 3.0% to 5.0% (by weight).

[0029] The aforementioned weight ratio is equivalent to "weight ratio" or "mass ratio", which is a comparative display of the feeding amounts of two or more raw materials in the preparation process.

[0030] Beneficial effects of the present invention:

[0031] 1. The composite nucleating agent of the present invention is made of existing nucleating agents, and does not need to be prepared by complex processes such as microspheres and microemulsions with harsh process conditions and low yields, and the preparation method is simple. Compared with other polymer nucleating agents, no highly polluting reagents are used and the preparation cost is low.

[0032] 2. The light transmittance of thermoplastic polyurethane elastomer material, namely TPU material, is related to complex factors such as molecular structure, molecular weight size and distribution, and processing method. TPU material itself has certain light transmittance, but when various additives are added to improve the performance of TPU, due to the refractive index of the additives, the compatibility of the additives with TPU and other issues, it is easy to enhance the matte effect and reduce the light transmittance of TPU material. The present invention selects an inorganic nucleating agent to modify its surface, and then chelates with an organic nucleating agent and an antioxidant to form a composite nucleating agent, thereby improving the optical properties of the nucleating agent and inhibiting the precipitation of the nucleating agent from the TPU material, thereby reducing the matte effect caused by the addition of additives, maintaining and improving the light transmittance of the TPU film, especially the light transmittance in a high temperature and high humidity environment.

[0033] 3. The composite nucleating agent of the present invention can guide the crystallization of TPU materials under high temperature conditions and has good compatibility with TPU polyester materials, thereby improving the processing efficiency of TPU.

[0034] 4. The composite nucleating agent of the present invention and TPU polyester particles are used to make a TPU film, which can also effectively reduce the transverse and longitudinal shrinkage of the TPU film, reduce the curling of the TPU film during the winding process and the generation of wrinkles in the TPU film after unfolding; and can improve the strength of the TPU film.

[0035] 5. The TPU film of the present invention first uses a composite nucleating agent and TPU polyester particles to prepare a master batch using a twin-screw extruder, and then the film is made. The dispersibility of the composite nucleating agent in the TPU material can be improved by using a twin-screw extruder for granulation, thereby facilitating the preparation of the TPU film and reducing the agglomeration of the composite nucleating agent in the TPU material. After the master batch is prepared using a twin-screw extruder, it is beneficial to reduce dust in the film-making workshop and improve the cleanliness of the equipment and the film surface. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the specific embodiments are only used to explain the present invention and are not used to limit the scope of protection of the present invention.

[0037] The material selection information of the inorganic nanopowder nucleating agent used in the following examples and comparative examples is as follows:

[0038] Fumed mesoporous silica: average particle size 150nm; optical refractive index: 1.46;

[0039] Co-precipitated hydrotalcite: average particle size 160nm; optical refractive index: 1.54;

[0040] Artificial glass microspheres: average particle size 140nm; optical refractive index: 1.51;

[0041] Nano sodium silicate: average particle size 140nm; optical refractive index: 1.52;

[0042] Nano-mica powder: average particle size 140nm; optical refractive index: 1.49.

[0043] Example 1 Preparation of a composite nucleating agent and TPU film

[0044] 1. Preparation of composite nucleating agent:

[0045] (1) 180.0 g of gas phase mesoporous silica nucleating agent was ultrasonically dispersed in a mixed solution of 2100 mL of methanol and water (the volume ratio of methanol to water was 1:0.1), 14.2 g of γ-(ethylenediamino)propyltrimethoxysilane was added, and ammonia water was added dropwise to adjust the pH of the mixed suspension to 9-10, and the mixture was reacted at 93°C for 3.5 h. After the reaction, the reaction solution was centrifuged and washed, and the precipitate was dried and ground to obtain modified nano-silica powder.

[0046] (2) Take 170.0g of modified nano-silica powder, add 0.08g of antioxidant 1076 and 0.04g of antioxidant 608, stir at 95rpm and heat to 110°C, add 30.0g of di[2,2-methylene-di(4,6-di-tert-butylphenyl)carboxylate]hydroxyaluminum, and react at 0.9MPa for 14h. After the reaction, grind the mixture and pass it through a 200-mesh sieve to obtain a composite nucleating agent.

[0047] 2. Preparation of TPU film:

[0048] (1) Take 180.0 g of the composite nucleating agent, mix it with 4700 g of Lubrizol BF85 film-grade polyester TPU resin particles, and use a twin-screw extruder to granulate to prepare a composite nucleating agent-TPU mixed masterbatch. The content of the composite nucleating agent in the composite nucleating agent-TPU mixed masterbatch (mass percentage, %) is: [180 / (180+4700)]x100=3.69%.

[0049] (2) Take 4 kg of composite nucleating agent-TPU mixed masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of composite nucleating agent in TPU film (mass percentage, ‰): [4x3.69% / (4+50)]x1000=2.73‰.

[0050] Example 2 Preparation of a composite nucleating agent and TPU film

[0051] 1. Preparation of composite nucleating agent:

[0052] (1) 220.0 g of coprecipitated hydrotalcite was ultrasonically dispersed in a mixed solution of 2400 mL of methanol and water (the volume ratio of methanol to water was 1:0.15), 14.0 g of γ-aminopropyltriethoxysilane was added, and ammonia water was added dropwise to adjust the pH of the mixed suspension to 9-10. The mixture was reacted at 85°C for 4 h. After the reaction, the reaction solution was centrifuged and washed, and the precipitate was dried and ground to obtain modified nano-hydrotalcite powder.

[0053] (2) Take 210.0g of modified nano-hydrotalcite powder, add 0.4g of antioxidant 1010 and 0.6g of antioxidant 618, stir at 90rpm and heat to 110℃, add 42.0g of 2,2-methylene-bis(4,6-di-tert-butylphenyl) sodium phosphate, and react at 1.2Mpa for 12h. After the reaction, grind the mixture and pass it through a 200-mesh sieve to obtain a composite nucleating agent.

[0054] 2. Preparation of TPU film:

[0055] (1) Take 235.0 g of the composite nucleating agent, mix it with 5400 g of Lubrizol BF85 film-grade polyester TPU resin particles, and use a twin-screw extruder to granulate to prepare a composite nucleating agent-TPU mixed masterbatch. The content of the composite nucleating agent in the composite nucleating agent-TPU mixed masterbatch (mass percentage, %) is: [235 / (235+5400)]x100=4.17%.

[0056] (2) Take 3.5 kg of composite nucleating agent-TPU mixed masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of composite nucleating agent in TPU film (mass percentage, ‰): [3.5x4.17% / (3.5+50)]x1000=2.72‰.

[0057] Example 3 Preparation of a composite nucleating agent and TPU film

[0058] 1. Preparation of composite nucleating agent:

[0059] (1) 180.0 g of artificial glass microspheres were ultrasonically dispersed in a mixed solution of 2100 mL of methanol and water (the volume ratio of methanol to water was 1:0.12), 14.2 g of γ-(ethylenediamino)propyltrimethoxysilane was added, and ammonia water was added dropwise to adjust the pH of the mixed suspension to 9-10. The mixture was reacted at 93 °C for 3.5 h. After the reaction, the reaction solution was centrifuged and washed, and the precipitate was dried and ground to obtain modified nano-glass microsphere powder.

[0060] (2) Take 170.0g of modified nano-glass microbead powder, add 0.08g of antioxidant 1076 and 0.04g of antioxidant 608, stir and heat to 110°C, add 30.0g of N,N-dicyclohexyl terephthalamide, and react at 0.9MPa for 14h. After the reaction, grind the mixture and pass it through a 200-mesh sieve to obtain a composite nucleating agent.

[0061] 2. Preparation of TPU film:

[0062] (1) Take 170.0g of the composite nucleating agent, mix it evenly with 4400g of Lubrizol BF85 film-grade polyester TPU resin particles, and use a twin-screw extruder to granulate to prepare a composite nucleating agent TPU mixed masterbatch; take the composite nucleating agent TPU mixed masterbatch, and use the extrusion casting method to prepare a TPU film. The content of the composite nucleating agent in the TPU film (mass percentage, %): [170 / (170+4400)]x100=3.72%.

[0063] (2) Take 4.0 kg of composite nucleating agent-TPU mixed masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of composite nucleating agent in TPU film (mass percentage, ‰): [4x3.72% / (4+50)]x1000=2.76‰.

[0064] Example 4 Preparation of a composite nucleating agent and TPU film

[0065] 1. Preparation of composite nucleating agent:

[0066] (1) Ultrasonic dispersion of 210.0 g of nano-sodium silicate in a mixed solution of 2700 mL of methanol and water (the volume ratio of methanol to water is 1:0.16), adding 12.6 g of anilinomethyltriethoxysilane, dropping ammonia water to adjust the pH of the mixed suspension to 9-10, and reacting at 97°C for 4.5 h. After completion, the reaction solution was centrifuged and washed, the precipitate was dried, and ground to obtain modified nano-sodium silicate powder.

[0067] (2) Take 200.0g of modified nano-sodium silicate powder, add 0.18g of antioxidant 225, stir and heat to 105°C, add 48.0g of di-(p-methylbenzylidene) sorbitol, and react at 1.0MPa for 20h. After the reaction, grind the mixture and pass it through a 200-mesh sieve to obtain a composite nucleating agent.

[0068] 2. Preparation of TPU film:

[0069] (1) Take 230.0g of the composite nucleating agent, mix it evenly with 7400g of Lubrizol BF85 film-grade polyester TPU resin particles, and use a twin-screw extruder to granulate to prepare a composite nucleating agent TPU mixed masterbatch; take the composite nucleating agent TPU mixed masterbatch, and use the extrusion casting method to prepare a TPU film. The content of the composite nucleating agent in the TPU film (mass percentage, %): [230 / (230+7400)]x100=3.01%.

[0070] (2) Take 5 kg of composite nucleating agent-TPU mixed masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of composite nucleating agent in TPU film (mass percentage, ‰): [5x3.01% / (5+50)]x1000=2.74‰.

[0071] Example 5 Preparation of a composite nucleating agent and TPU film

[0072] 1. Preparation of composite nucleating agent:

[0073] (1) Ultrasonic dispersion of 260.0 g of nano-mica powder in a mixed solution of 3000 mL of methanol and water (the volume ratio of methanol to water is 1:0.15), adding 21.1 g of γ-methacryloxypropyltrimethoxysilane, dropping ammonia water to adjust the pH of the mixed suspension to 9-10, and reacting at 95 °C for 4 h. After completion, the reaction solution was centrifuged and washed, the precipitate was dried, and ground to obtain modified nano-mica powder.

[0074] (2) Take 250.0g of modified nano-mica powder, add 0.20g of antioxidant 215, stir and heat to 115°C, add 60.0g of sodium β-naphthoate, and react at 1.3MPa for 18h. After the reaction, grind the mixture and pass it through a 200-mesh sieve to obtain a composite nucleating agent.

[0075] 2. Preparation of TPU film:

[0076] (1) 300.0 g of a composite nucleating agent was obtained and mixed evenly with 5900 g of Lubrizol BF85 film-grade polyester TPU resin particles, and the composite nucleating agent TPU mixed masterbatch was prepared by granulation using a twin-screw extruder; the composite nucleating agent TPU mixed masterbatch was taken and a TPU film was prepared by an extrusion casting method. The content of the composite nucleating agent in the TPU film (mass percentage, %): [300 / (300+5900)]x100=4.84%.

[0077] (2) Take 3 kg of composite nucleating agent-TPU mixed masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of composite nucleating agent in TPU film (mass percentage, ‰): [3x4.84% / (3+50)]x1000=2.74‰.

[0078] Comparative Example 1: A TPU film and its preparation

[0079] Without adding other additives, the TPU film is made by extrusion casting method using only Lubrizol BF85 film-grade polyester TPU resin particles.

[0080] Comparative Example 2: A TPU film and its preparation

[0081] (1) 65.0 g of co-precipitated hydrotalcite inorganic nucleating agent was mixed evenly with 1500 g of Lubrizol BF85 film-grade polyester TPU resin particles, and granulated using a twin-screw extruder to prepare an inorganic nucleating agent-TPU mixed masterbatch; the content of the inorganic nucleating agent in the inorganic nucleating agent-TPU mixed masterbatch (mass percentage, %): [65 / (65+1500)]x100=4.15%.

[0082] (2) Take 3.5 kg of inorganic nucleating agent-TPU mixed masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of inorganic nucleating agent in TPU film (mass percentage, ‰): [3.5x4.15% / (3.5+50)]x1000=2.71‰.

[0083] Comparative Example 3: A TPU film and its preparation

[0084] (1) Take 50.0g of bis(3,4-dimethyl)-diphenylmethylene sorbitol organic nucleating agent, mix it evenly with 1300g of Lubrizol BF85 film-grade polyester TPU resin particles, and use a twin-screw extruder to granulate to prepare organic nucleating agent-TPU mixed masterbatch. The content of organic nucleating agent in organic nucleating agent-TPU mixed masterbatch (mass percentage, %) is: [50 / (50+1300)]x100=3.70%.

[0085] (2) Take 4 kg of organic nucleating agent-TPU mixed masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of inorganic nucleating agent in TPU film (mass percentage, ‰): [4x3.70% / (4+50)]x1000=2.74‰.

[0086] Comparative Example 4: A TPU film and its preparation

[0087] (1) 120 g of nano sodium silicate was ultrasonically dispersed in a mixed solution of 2400 mL of methanol and water (the volume ratio of methanol to water was 1:0.15), 6.4 g of vinyl triethoxysilane was added, and ammonia water was added dropwise to adjust the pH of the mixed suspension to 9-10, and the mixture was reacted at 85°C for 4 h. After the reaction, the reaction solution was centrifuged and washed, and the precipitate was dried and ground to obtain modified nano sodium silicate powder.

[0088] (2) Take 120 g of modified nano-sodium silicate powder, add 0.1 g of antioxidant 225 and 20 g of sodium bicyclo (2,2,1) heptene-2,3-dicarboxylate, mix evenly with 3160 g of Lubrizol BF85 film-grade polyester TPU resin particles, and use a twin-screw extruder to granulate to prepare a mixed nucleating agent-TPU mixed masterbatch; the content of the mixed nucleating agent in the mixed nucleating agent-TPU mixed masterbatch (mass percentage, %): [(120+20) / (120+20+3160)]x100=4.24%.

[0089] (3) Take 3.5 kg of mixed nucleating agent-TPU masterbatch and mix it with 50 kg of Lubrizol BF85 film-grade polyester TPU resin particles, and use extrusion casting to make TPU film. The content of inorganic nucleating agent in TPU film (mass percentage, ‰): [3.5x4.24% / (3.5+50)]x1000=2.77‰.

[0090] Example 6 Performance test of TPU film

[0091] The performance tests were conducted on the TPU films of Examples 1-5 and Comparative Examples 1-4, and the test indicators and methods were as follows:

[0092] (1) The crystallinity and crystallization temperature of the TPU film were tested using a differential scanning calorimeter (DSC). The test standard was to increase the temperature from room temperature to 220°C at a heating rate of 10°C / min, balance for 3 minutes, and then cool down to -40°C at a cooling rate of 10°C / min.

[0093] (2) Lay the newly prepared TPU film (1.50 m × 1.50 m) flat and observe the transverse and longitudinal shrinkage of the TPU film after 8 hours.

[0094] (3) Refer to GB 2410-80 (89) "Test method for light transmittance and haze of transparent plastics" to test the haze and light transmittance of TPU films of equal thickness.

[0095] (4) Test the breaking strength and elongation of TPU film with reference to ISO 1184-1983 “Determination of tensile properties of plastic films”.

[0096] Test results:

[0097] (1) Results of determination of TPU film molding efficiency-related indicators (crystallinity, crystallization temperature)

[0098] The crystallinity, initial crystallization temperature and maximum crystallization rate temperature of different TPU film samples are shown in Table 1. The test found that the crystallinity of Comparative Example 1, as a TPU film without any additives, was 27.3%, while the crystallinity of the TPU films of Examples 1 to 5 was greater than 27.3%, indicating that the use of a composite nucleating agent to improve the performance of TPU materials effectively improves the crystallinity of TPU films.

[0099] In addition, the initial crystallization temperature of the TPU film in Comparative Example 1 is 142.1°C, and the maximum crystallization rate temperature is 127.6°C, while the initial crystallization temperatures of the TPU films in Examples 1 to 5 are all greater than 142.1°C, and the maximum crystallization rate temperatures are also greater than 127.6°C, indicating that the composite nucleating agent can guide the TPU material to crystallize under high temperature conditions. This is conducive to improving the processing efficiency of TPU.

[0100] Table 1 Crystallinity and crystallization temperature of TPU film

[0101]

[0102] (2) Test results of TPU film curling and shrinkage related indicators (shrinkage rate):

[0103] The transverse and longitudinal shrinkage rates of different TPU film samples are shown in Table 2. It was found that the transverse shrinkage rate of the TPU film of Comparative Example 1 reached 3.94%, the longitudinal shrinkage rate reached 1.84%, and the dimensional stability within 8 hours was poor; while the transverse shrinkage rates of the TPU films of Examples 1 to 5 were all less than 1.00%, and the longitudinal shrinkage rates were all less than 0.20%, indicating that the composite nucleating agent effectively improves the dimensional stability of the TPU film, which is beneficial to reduce the occurrence of film curling and shrinkage.

[0104] Table 2 Transverse / vertical shrinkage of TPU film

[0105]

[0106] (3) Test results of TPU film transmittance related indicators (transmittance and haze):

[0107] The transmittance and haze of different TPU film samples are shown in Table 3. The test found that when tested immediately: the transmittance of the TPU film in Example 1 reached 90.32%, and the haze value was 6.51%. The transmittance of the TPU film in Example 2 using an inorganic nucleating agent dropped to 78.54%, and the haze value rose to 10.16%; the transmittance of the TPU film in Example 3 using an organic nucleating agent was 90.78%, and the haze value was 6.47%. The transmittance of the TPU film in Example 4 using a simple mixed modified inorganic nucleating agent / organic nucleating agent / antioxidant was 85.09%, and the haze value was 9.87%. When tested after treatment in a high temperature and high humidity environment, the transmittance of the TPU film with the addition of additives decreased and the haze increased, which was attributed to the powder precipitation behavior of the powder on the surface of the TPU film, which affected the transmission of light. However, the light transmittance of the TPU film of Examples 1-5 decreases less, and the light transmittance of the TPU film after high temperature and high humidity treatment is still higher than that of the TPU film of Comparative Examples 1-4, and the haze is also better than that of the TPU film of Comparative Examples 1-4.

[0108] Combined with the relevant data in Table 1 and Table 2, it is shown that filling the unmodified inorganic and organic nucleating agents into the TPU material can improve the crystallinity and crystallization temperature of the TPU film to a certain extent and reduce the shrinkage of the TPU film, but it will cause the light transmittance of the TPU film to decrease and the matte effect to increase. The light transmittance of the TPU film modified by the composite nucleating agent is greater than 92.00%, and the haze value is less than 6.00%. Even after high temperature and high humidity treatment, the light transmittance of the TPU film with the composite nucleating agent is still high, indicating that the addition of the new nucleating agent will not cause the high permeability of the TPU film to decrease.

[0109] Table 3 Transmittance and haze of TPU film

[0110]

[0111] Note: High temperature and high humidity environment treatment is used to characterize the migration ability of additives inside polymer materials. The test temperature is 85°C, the humidity is 85%, and the test time is 168h. That is, the transmittance and haze of the TPU film are measured after being treated in a high temperature and high humidity environment.

[0112] (4) Test results of TPU film mechanical properties related indicators (strength):

[0113] The breaking strength and breaking elongation of different groups of TPU film samples are shown in Table 4. The test found that the longitudinal and transverse breaking strengths of the TPU film of Comparative Example 1 were 76.6MPa and 70.3MPa, respectively, and the longitudinal and transverse breaking elongations were 614% and 682%, respectively. The longitudinal and transverse breaking strengths and longitudinal and transverse breaking elongations of the TPU films of Examples 1 to 5 were close to those of Comparative Example 1, indicating that the addition of the composite nucleating agent will not cause a significant decrease in the mechanical properties of the TPU film, but will increase them to a certain extent.

[0114] Table 4 Breaking strength and breaking elongation of TPU film

[0115]

[0116] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The above description of the disclosed embodiments enables professional and technical personnel in this field to realize or implement the present invention.

[0117] The multiple modification / replacement of these embodiments will be apparent to those skilled in the art, and the general principle defined herein can be realized in other embodiments without departing from the spirit or scope of the present invention. For example, this area is known to the preferred particle size range of the inorganic nano powder as nucleating agent, and has more prior art documents for reference. Therefore, without departing from the spirit or scope of the present invention, the particle size range of the inorganic nano powder is not limited to the scope of the embodiments. Therefore, the present invention will not be limited to these embodiments, but should be the widest range consistent with principle disclosed herein.

Claims

1. A TPU film prepared by using a composite nucleating agent for TPU film, characterized in that: The TPU film is made of film-grade polyester TPU resin particles and a composite nucleating agent, and the content of the composite nucleating agent in the TPU film is 2.6‰~3.0‰; The preparation method of the composite nucleating agent comprises the following steps: S1 Preparation of modified inorganic nanopowder: dispersing an inorganic nanopowder nucleating agent in a methanol-water mixed solution, adding a silane coupling agent, reacting at a pH value of 9 to 10 and 70° C. to 100° C., and after the reaction is completed, drying the precipitate to obtain a modified inorganic nanopowder; S2 Preparation of composite nucleating agent: Take the modified inorganic nanopowder obtained in step S1, add antioxidant, heat to 100°C-150°C, add organic nucleating agent, react under 0.5Mpa-2.0Mpa, reaction time is 8h-30h, after the reaction is completed, grind the mixture, sieve to obtain composite nucleating agent; The preparation method of the TPU film comprises the following steps: T1 Preparation of composite nucleating agent-TPU mixed masterbatch: film-grade polyester TPU resin particles and composite nucleating agent are added into a twin-screw extruder for granulation to prepare composite nucleating agent-TPU mixed masterbatch; T2 TPU film preparation: Take the composite nucleating agent-TPU mixed masterbatch obtained in step T1 and add film-grade polyester TPU resin particles to make a TPU film by extrusion casting method; In step S1, the weight ratio of the inorganic nanopowder nucleating agent to the silane coupling agent is (10-35):(1-5); In step S1, the silane coupling agent is selected from at least one of γ-(ethylenediamino)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, anilinomethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, and vinyltri(2-methoxyethoxy)silane; In step S2, the weight ratio of the modified inorganic nanopowder, antioxidant, and organic nucleating agent is (100-350):(0.1-0.5):(10-200); In step S2, the organic nucleating agent is at least one of a carboxylic acid metal salt nucleating agent, a phosphate metal salt nucleating agent, a sorbitol benzyl derivative nucleating agent, and an aromatic diamide nucleating agent; In step T1, the content of the composite nucleating agent in the composite nucleating agent-TPU mixed masterbatch is 3.0% to 5.0%.

2. The TPU film according to claim 1, characterized in that The content of the composite nucleating agent in the TPU film is 2.7‰~2.8‰.

3. The TPU film according to claim 1, characterized in that: In step S1, the average particle size of the inorganic nanopowder nucleating agent is 20nm~500nm.

4. The TPU film according to claim 1, characterized in that In step S1, the optical refractive index of the inorganic nanopowder nucleating agent is 1.35-1.

55.

5. The TPU film according to claim 1, characterized in that: In step S1, the methanol-water mixed solution is prepared by using methanol and water in a volume ratio of 1: (0.1-1.2).

6. The TPU film according to claim 1, characterized in that: In step S1, the reaction temperature is 80°C to 100°C.

7. The TPU film according to claim 1, characterized in that: In step S1, the reaction time is 3h~7h.

8. The TPU film according to claim 1, characterized in that In step S2, the antioxidant is a composite antioxidant composed of a hindered phenol antioxidant and a phosphite antioxidant.

9. The TPU film according to claim 8, characterized in that: The weight ratio of the hindered phenol antioxidant to the phosphite antioxidant in the composite antioxidant is (1-3):(1-5).

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