High-strength bio-based TPU (thermoplastic polyurethane) film with controllable degradation characteristic and preparation method of high-strength bio-based TPU film

Abstract

The invention relates to the technical field of thermoplastic polyurethane elastomer composite materials, in particular to a high-strength bio-based TPU film with a controllable degradation characteristic and a preparation method of the high-strength bio-based TPU film. The high-strength bio-based TPU film with the controllable degradation characteristic is prepared from the following raw materials in parts by mass: 50 to 100 parts of thermoplastic polyurethane elastomer, 10 to 25 parts of polycaprolactone, 1 to 2 parts of polylactic acid, 1 to 3 parts of microcrystalline cellulose, 1 to 5 parts of tetraethoxysilane, 5 to 10 parts of silicon dioxide micro powder, 1 to 2 parts of a biodegradation accelerant, 1 to 2 parts of a slipping agent, 1 to 2 parts of an anti-blocking agent and 0.25 to 0.5 part of an antioxidant. The TPU film has the characteristic of controllable environmental degradation while keeping high strength, the contradiction between the mechanical property and the degradation property of a traditional TPU film is broken through, a direction is provided for green application of the bio-based TPU film, and meanwhile, the preparation method is simple and suitable for large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic polyurethane elastomer composite materials, and in particular to a high-strength bio-based TPU film with controllable degradation properties and its preparation method. Background Technology

[0002] Thermoplastic polyurethane elastomer (TPU), as a block copolymer, possesses excellent mechanical, thermal, and processing properties due to its unique microphase separation structure of soft and hard segments. TPU films, manufactured through processes such as calendering and casting, have become an ideal alternative to traditional PVC due to their superior abrasion resistance, solvent resistance, and stability, and are widely used in footwear, medical devices, and automotive interiors.

[0003] However, TPU films have a dense molecular structure, resulting in a long natural decomposition cycle. After disposal, they easily accumulate in the environment, forming white pollution. Although existing technologies address this through incineration or recycling, incineration releases harmful gases, while recycling requires complex impurity separation, which is costly and inefficient.

[0004] Currently, it is difficult to simultaneously achieve good degradation performance and mechanical properties in TPU films. While introducing biodegradable materials can accelerate decomposition, it leads to a significant decrease in film strength, affecting its application value as a functional material. For example, adding bio-based components may disrupt the balance between hard and soft segments, reducing tensile strength and elastic modulus, making the film prone to breakage under load or tension. This contradiction has become a key bottleneck in the green development of TPU films.

[0005] Currently, the development of bio-based TPU films that combine controllable degradation characteristics and high strength to balance environmental protection requirements and material performance has excellent research prospects. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-strength bio-based TPU film with controllable degradation properties and its preparation method.

[0007] A high-strength bio-based TPU film with controllable degradation properties, comprising the following raw materials by weight: 50-100 parts thermoplastic polyurethane elastomer, 10-25 parts polycaprolactone, 1-2 parts polylactic acid, 1-3 parts microcrystalline cellulose, 1-5 parts tetraethyl orthosilicate, 5-10 parts silica powder, 1-2 parts biodegradation promoter, 1-2 parts slip agent, 1-2 parts antiblocking agent, and 0.25-0.5 parts antioxidant.

[0008] Preferably, the antioxidant is at least one of antioxidant 1010, tri(nonylphenyl) phosphite, bisphenol A phosphite, and triphenyl phosphite.

[0009] Preferably, the slip agent is at least one of erucamide, stearamide, and zinc stearate.

[0010] Preferably, the anti-blocking agent is talc.

[0011] Preferably, the biodegradation promoter is citric acid.

[0012] Preferably, the silica micro powder is obtained by treating nano-silica with a silane coupling agent.

[0013] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. Add tetraethyl orthosilicate to an ethanol aqueous solution and stir until homogeneous. Add microcrystalline cellulose and mix until homogeneous. Adjust the pH of the system to 3-4. Stir at 40-60℃ for 1-3 hours. Cool to 2-6℃, filter, wash, freeze dry, pulverize and sieve to obtain composite fiber. S2. After vacuum drying the thermoplastic polyurethane elastomer and polycaprolactone, mix them together, then add the composite fiber and stir for 1-5 minutes to obtain the premix. S3. Mix silica micro powder, antioxidant, polylactic acid, slip agent, anti-blocking agent and biodegradation promoter evenly, add to premix and stir for 5-15 minutes, melt extrude at 180-200℃ and blow mold to form a film.

[0014] Preferably, in S1, the pH of the system is adjusted to 3-4 using hydrochloric acid with a concentration of 1-2 mol / L.

[0015] Preferably, in S1, the aspect ratio of the composite fiber is 20-40.

[0016] Preferably, in S3, the blow-in ratio during the blow molding process is 1:2-4.

[0017] Beneficial effects: This invention utilizes the hydrolysis and condensation of tetraethyl orthosilicate and microcrystalline cellulose under acidic conditions to form porous silica-cellulose composite fibers. These fibers have a three-dimensional network structure that can be uniformly dispersed within a TPU matrix. Through hydrogen bonding, they can enhance the tensile strength and elastic modulus of the film. Simultaneously, the hydrophilicity of cellulose promotes the formation of micropores on the film surface, accelerating the penetration of environmental moisture and creating initial conditions for subsequent biodegradation. This invention introduces composite fibers without disrupting the microphase separation structure of the TPU's soft and hard segments, avoiding the mechanical property degradation often associated with traditional bio-based materials.

[0018] Polycaprolactone, as a semi-crystalline polyester, has ester bonds that are easily hydrolyzed and broken by microorganisms. It can form a blend system with TPU hard segments, which can enhance mechanical properties through molecular chain segment synergy. At the same time, the certain crystallinity of polycaprolactone gives the material initial rigidity, thus effectively maintaining the dimensional stability of the film during degradation. Its synergistic effect with composite fibers can not only slow down the decline of mechanical properties in the early stage of degradation, but also achieve the gradual degradation of the film by regulating the moisture diffusion rate.

[0019] This invention enables TPU films to maintain high strength while possessing controllable environmental degradation characteristics, breaking through the contradiction between the mechanical properties and degradation performance of traditional TPU films. It provides a direction for the green application of bio-based TPU films, and the preparation method is simple and suitable for large-scale promotion and application. Attached Figure Description

[0020] Figure 1 The graph shows a comparison of the tensile strength and tensile strength retention rate of the TPU films obtained in Example 5 and Comparative Examples 1-2 after 42 days of hydrolysis.

[0021] Figure 2 The tensile strength retention rate of the TPU films obtained in Example 5 and Comparative Examples 1-2 after soil degradation. Detailed Implementation

[0022] The present invention will be further explained below with reference to specific embodiments.

[0023] The thermoplastic polyurethane elastomer used below is sourced from Wanhua Chemical, brand name WHT-1180H. The polycaprolactone used below is sourced from Perstork, Sweden, brand name Capa 6500. The silica micropowder used below is obtained by treating nano-silica with silane coupling agent KH550.

[0024] Example 1 A high-strength bio-based TPU film with controllable degradation properties, the raw materials of which include: 500g thermoplastic polyurethane elastomer, 100g polycaprolactone, 10g polylactic acid, 10g microcrystalline cellulose, 10g tetraethyl orthosilicate, 50g silica powder, 10g citric acid, 10g stearamide, 10g talc, and 2.5g antioxidant 1010.

[0025] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. Add tetraethyl orthosilicate to 200g of 40% ethanol aqueous solution and stir until homogeneous. Add microcrystalline cellulose and mix until homogeneous. Adjust the pH of the system to 3-4 using 1mol / L hydrochloric acid. Stir at 40℃ for 1h, cool to 2℃, filter, wash, freeze dry, and pulverize through a 100-mesh sieve to obtain composite fiber. S2. The thermoplastic polyurethane elastomer and polycaprolactone are vacuum dried at 40°C, mixed and then the composite fiber is added. The mixture is stirred at 1000 r / min for 1 min to obtain a premix. S3. Mix silica micro powder, antioxidant 1010, polylactic acid, stearamide, talc, and citric acid evenly, add them to the premix, stir at 400 r / min for 5 min, feed them into a twin-screw extruder for melt extrusion, set the melt temperature to 180℃, and use compressed air to blow them into cylindrical film bubbles to form a film, wherein the blow-up ratio is 1:2 and the film thickness is 95μm.

[0026] Example 2 A high-strength bio-based TPU film with controllable degradation properties, the raw materials of which include: 1000g thermoplastic polyurethane elastomer, 250g polycaprolactone, 20g polylactic acid, 30g microcrystalline cellulose, 50g tetraethyl orthosilicate, 100g silica powder, 20g citric acid, 20g zinc stearate, 20g talc, and 5g antioxidant 1010.

[0027] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. Add tetraethyl orthosilicate to 400g of 60% ethanol aqueous solution and stir evenly. Add microcrystalline cellulose and mix evenly. Adjust the pH of the system to 3-4 with 2mol / L hydrochloric acid. Stir at 60℃ for 3h, cool to 6℃, filter, wash, freeze dry, and pulverize through a 100-mesh sieve to obtain composite fiber. S2. The thermoplastic polyurethane elastomer and polycaprolactone are vacuum dried at 60℃, mixed and then the composite fiber is added. The mixture is stirred at 2000r / min for 5min to obtain a premix. S3. Mix silica micro powder, antioxidant 1010, polylactic acid, zinc stearate, talc, and citric acid evenly, add them to the premix, stir at 1000 r / min for 15 min, feed them into a twin-screw extruder for melt extrusion, set the melt temperature to 200℃, and use compressed air to blow up cylindrical film bubbles to form a film, wherein the blow-up ratio is 1:4 and the film thickness is 60μm.

[0028] Example 3 A high-strength bio-based TPU film with controllable degradation properties, the raw materials of which include: 700g thermoplastic polyurethane elastomer, 200g polycaprolactone, 18g polylactic acid, 15g microcrystalline cellulose, 40g tetraethyl orthosilicate, 70g silica powder, 18g citric acid, 13g erucamide, 17g talc, and 3.5g antioxidant 1010.

[0029] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. Add tetraethyl orthosilicate to 250g of 55% ethanol aqueous solution and stir until homogeneous. Add microcrystalline cellulose and mix until homogeneous. Adjust the pH of the system to 3.5 with 1.5mol / L hydrochloric acid. Stir at 45℃ for 2.5h, cool to 3℃, filter, wash, freeze dry, and pulverize through a 100-mesh sieve to obtain composite fiber. S2. The thermoplastic polyurethane elastomer and polycaprolactone are vacuum dried at 45°C, mixed and then the composite fiber is added. The mixture is stirred at 1800 r / min for 2 min to obtain a premix. S3. Mix silica micro powder, antioxidant 1010, polylactic acid, erucamide, talc, and citric acid evenly, add them to the premix, stir at 800 r / min for 8 min, and feed them into a twin-screw extruder for melt extrusion. Set the melt temperature to 195℃, and use compressed air to blow up the film into a cylindrical bubble to form a film. The blow-up ratio is 1:2.5, and the film thickness is 75 μm.

[0030] Example 4 A high-strength bio-based TPU film with controllable degradation properties, the raw materials of which include: 900g thermoplastic polyurethane elastomer, 150g polycaprolactone, 12g polylactic acid, 25g microcrystalline cellulose, 20g tetraethyl orthosilicate, 90g silica powder, 12g citric acid, 17g erucamide, 13g talc, and 4.5g antioxidant 1010.

[0031] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. Add tetraethyl orthosilicate to 350g of 45% ethanol aqueous solution and stir evenly. Add microcrystalline cellulose and mix evenly. Adjust the pH of the system to 3.5 with 1.5mol / L hydrochloric acid. Stir at 55℃ for 1.5h, cool to 5℃, filter, wash, freeze dry, and pulverize through a 100-mesh sieve to obtain composite fiber. S2. The thermoplastic polyurethane elastomer and polycaprolactone are vacuum dried at 55°C, mixed and then the composite fiber is added. The mixture is stirred at 1200 r / min for 4 min to obtain a premix. S3. Mix silica micro powder, antioxidant 1010, polylactic acid, erucamide, talc, and citric acid evenly, add them to the premix, stir at 600 r / min for 12 min, and feed them into a twin-screw extruder for melt extrusion. Set the melt temperature to 185℃, and use compressed air to blow up the film into a cylindrical bubble to form a film. The blow-up ratio is 1:3.5, and the film thickness is 75 μm.

[0032] Example 5 A high-strength bio-based TPU film with controllable degradation properties, the raw materials of which include: 800g thermoplastic polyurethane elastomer, 180g polycaprolactone, 15g polylactic acid, 20g microcrystalline cellulose, 30g tetraethyl orthosilicate, 80g silica powder, 15g citric acid, 15g erucamide, 15g talc, and 4g antioxidant 1010.

[0033] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. Add tetraethyl orthosilicate to 300g of 50% ethanol aqueous solution and stir evenly. Add microcrystalline cellulose and mix evenly. Adjust the pH of the system to 3.5 with 1.5mol / L hydrochloric acid. Stir at 50℃ for 2h, cool to 4℃, filter, wash, freeze dry, and pulverize through a 100-mesh sieve to obtain composite fiber. S2. The thermoplastic polyurethane elastomer and polycaprolactone are vacuum dried at 50°C, mixed and then the composite fiber is added. The mixture is stirred at 1500 r / min for 3 min to obtain a premix. S3. Mix silica micro powder, antioxidant 1010, polylactic acid, erucamide, talc, and citric acid evenly, add them to the premix, stir at 700 r / min for 10 min, feed them into a twin-screw extruder for melt extrusion, set the melt temperature to 190℃, and use compressed air to blow them into cylindrical film bubbles to form a film, wherein the blow-up ratio is 1:3 and the film thickness is 75μm.

[0034] Comparative Example 1 A high-strength bio-based TPU film with controllable degradation properties, the raw materials of which include: 800g thermoplastic polyurethane elastomer, 180g polycaprolactone, 15g polylactic acid, 20g microcrystalline cellulose, 30g tetraethyl orthosilicate, 80g silica powder, 15g citric acid, 15g erucamide, 15g talc, and 4g antioxidant 1010.

[0035] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. Add tetraethyl orthosilicate to 300g of 50% ethanol aqueous solution and stir evenly. Adjust the pH of the system to 3.5 with 1.5mol / L hydrochloric acid. Stir at 50℃ for 2h, cool to 4℃, filter, wash, freeze dry, pulverize and pass through a 100-mesh sieve. Add microcrystalline cellulose and mix evenly to obtain composite fiber. S2. The thermoplastic polyurethane elastomer and polycaprolactone are vacuum dried at 50°C, mixed and then the composite fiber is added. The mixture is stirred at 1500 r / min for 3 min to obtain a premix. S3. Mix silica micro powder, antioxidant 1010, polylactic acid, erucamide, talc, and citric acid evenly, add them to the premix, stir at 700 r / min for 10 min, feed them into a twin-screw extruder for melt extrusion, set the melt temperature to 190℃, and use compressed air to blow them into cylindrical film bubbles to form a film, wherein the blow-up ratio is 1:3 and the film thickness is 75μm.

[0036] Comparative Example 2 A high-strength bio-based TPU film with controllable degradation properties, the raw materials of which include: 800g thermoplastic polyurethane elastomer, 180g polycaprolactone, 15g polylactic acid, 50g microcrystalline cellulose, 80g silica powder, 15g citric acid, 15g erucamide, 15g talc, and 4g antioxidant 1010.

[0037] The method for preparing the above-mentioned high-strength bio-based TPU film with controllable degradation properties includes the following steps: S1. The thermoplastic polyurethane elastomer and polycaprolactone are vacuum dried at 50°C, mixed and then microcrystalline cellulose is added. The mixture is stirred at 1500 r / min for 3 min to obtain a premix. S2. Mix silica micro powder, antioxidant 1010, polylactic acid, erucamide, talc, and citric acid evenly, add them to the premix, stir at 700 r / min for 10 min, feed them into a twin-screw extruder for melt extrusion, set the melt temperature to 190℃, and use compressed air to blow up the film into a cylindrical bubble to form a film, wherein the blow-up ratio is 1:3 and the film thickness is 75μm.

[0038] The tensile strength of the TPU films obtained in Example 5 and Comparative Examples 1-2 was determined according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". Subsequently, the TPU films obtained in Example 5 and Comparative Examples 1-2 were placed in an 80°C water bath for hydrolytic stability testing. After 42 days, the films were removed and the tensile strength was measured again. The tensile strength retention rate after 42 days of hydrolysis was calculated.

[0039] like Figure 1 As shown, the TPU film obtained in Example 5 has the highest tensile strength and the highest tensile strength retention rate after 42 days of hydrolysis, which is significantly better than the comparative example.

[0040] The TPU films obtained in Example 5 and Comparative Examples 1-2 were buried in the soil for degradation. They were taken out on the 7th and 30th days, respectively, and the tensile strength was measured. The tensile strength retention rate after soil degradation was calculated.

[0041] like Figure 2As shown, the TPU film obtained in Example 5 exhibited a significantly higher tensile strength retention rate on day 7 compared to the comparative example, while the tensile strength retention rate on day 30 showed no significant difference compared to the comparative example. This confirms that the TPU film obtained by this invention can slow down the decline in mechanical properties during the initial stage of degradation, while accelerating biodegradation in the later stage, thus achieving gradual degradation of the film.

[0042] The reason for the above results is that this invention utilizes the hydrolysis and condensation of tetraethyl orthosilicate and microcrystalline cellulose under acidic conditions to form porous silicon-cellulose composite fibers. These fibers have a three-dimensional network structure that can be uniformly dispersed within the TPU matrix. Through hydrogen bonding, they can enhance the tensile strength and elastic modulus of the film. Simultaneously, the hydrophilicity of cellulose promotes the formation of micropores on the film surface, accelerating the penetration of environmental moisture and creating initial conditions for subsequent biodegradation. This invention introduces composite fibers without disrupting the microphase separation structure of the TPU's soft and hard segments, avoiding the mechanical property degradation caused by traditional bio-based materials. Polycaprolactone, as a semi-crystalline polyester, readily undergoes hydrolytic breakage of its ester bonds under microbial action, forming a blend system with the TPU hard segments. This synergistic effect of molecular chain segments enhances mechanical properties, while the certain crystallinity of polycaprolactone imparts initial rigidity to the material, effectively maintaining the dimensional stability of the film during degradation. The synergistic effect with the composite fibers not only slows down the decline in mechanical properties during the initial degradation phase but also achieves gradual degradation of the film by regulating the moisture diffusion rate.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-strength bio-based TPU film with controllable degradation properties, characterized in that, The raw materials, by weight, include: 50-100 parts thermoplastic polyurethane elastomer, 10-25 parts polycaprolactone, 1-2 parts polylactic acid, 1-3 parts microcrystalline cellulose, 1-5 parts tetraethyl orthosilicate, 5-10 parts silica powder, 1-2 parts biodegradation accelerator, 1-2 parts slip agent, 1-2 parts anti-blocking agent, and 0.25-0.5 parts antioxidant.

2. The high-strength bio-based TPU film with controllable degradation properties according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, tri(nonylphenyl) phosphite, bisphenol A phosphite, and triphenyl phosphite.

3. The high-strength bio-based TPU film with controllable degradation properties according to claim 1, characterized in that, The slip agent is at least one of erucamide, stearamide, and zinc stearate.

4. The high-strength bio-based TPU film with controllable degradation properties according to claim 1, characterized in that, The anti-blocking agent is talc.

5. The high-strength bio-based TPU film with controllable degradation properties according to claim 1, characterized in that, The biodegradation promoter is citric acid.

6. The high-strength bio-based TPU film with controllable degradation properties according to claim 1, characterized in that, Silica micro powder is obtained by treating nano-silica with a silane coupling agent.

7. A method for preparing a high-strength bio-based TPU film with controllable degradation properties as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Add tetraethyl orthosilicate to an ethanol aqueous solution and stir until homogeneous. Add microcrystalline cellulose and mix until homogeneous. Adjust the pH of the system to 3-4. Stir at 40-60℃ for 1-3 hours. Cool to 2-6℃, filter, wash, freeze dry, pulverize and sieve to obtain composite fiber. S2. After vacuum drying the thermoplastic polyurethane elastomer and polycaprolactone, mix them together, then add the composite fiber and stir for 1-5 minutes to obtain the premix. S3. Mix silica micro powder, antioxidant, polylactic acid, slip agent, anti-blocking agent and biodegradation promoter evenly, add to premix and stir for 5-15 minutes, melt extrude at 180-200℃ and blow mold to form a film.

8. The method for preparing a high-strength bio-based TPU film with controllable degradation properties according to claim 7, characterized in that, In S1, the pH of the system is adjusted to 3-4 using hydrochloric acid with a concentration of 1-2 mol / L.

9. The method for preparing a high-strength bio-based TPU film with controllable degradation properties according to claim 7, characterized in that, In S1, the aspect ratio of the composite fiber is 20-40.

10. The method for preparing a high-strength bio-based TPU film with controllable degradation properties according to claim 7, characterized in that, In S3, the blow-in ratio during the blow molding process is 1:2-4.

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