A multicolor flow-textured TPU film, its preparation method and application

Abstract

This invention relates to a multi-color textured TPU film, its preparation method, and its applications. The method includes: multi-color textured masterbatch preparation, casting process parameter setting, molding, and post-processing steps. This invention introduces multi-color TPU masterbatch and adjusts process parameters such as extrusion rate, screen mesh size, and die temperature based on the casting process to prepare a multi-color textured TPU film. This multi-color textured TPU film not only possesses excellent physical properties but also achieves multi-color, mixed-color, and textured visual effects from the same TPU film. The manufacturing process is simple, low-cost, and suitable for mass production.

Description

Technical Field

[0001] This invention relates to a multicolor flow-textured TPU film, its preparation method and application, belonging to the field of film material preparation technology. Background Technology

[0002] TPU film, a high-performance functional material, is produced by processing thermoplastic polyurethane elastomer (TPU) granules through a series of precise and targeted special processes, including calendering, casting, blown film production, and coating. These processes precisely control the film's thickness, structure, and properties according to different application requirements. TPU's unique molecular structure consists of both hard and soft segments. The hard segments, with their rigid, orderly arrangement, act like the material's "skeleton," giving TPU excellent tensile strength, making it less prone to breakage under tensile stress. They also provide excellent wear resistance, maintaining the integrity of the material surface even after prolonged friction, and grant TPU a certain degree of heat resistance, allowing for stable use in high-temperature environments. The soft segments, composed of flexible segments, act like "elastic springs" within the material. Through the free rotation and deformation between segments, TPU possesses rubber-like elasticity, enabling it to quickly return to its original shape after deformation. This combination of rigidity and flexibility in its molecular structure gives TPU films a multitude of excellent properties: its superior elasticity and flexibility allow it to adapt to various complex bending, folding, and other dynamic deformation scenarios, making it stand out in fields requiring frequent movement, such as footwear and clothing; its strong weather resistance means it can withstand long-term erosion from natural environmental factors such as ultraviolet rays, rain, and extreme temperatures, resulting in a service life far exceeding that of ordinary materials when used in outdoor products and automotive parts; its chemical corrosion resistance gives it excellent resistance to various chemicals such as acids, alkalis, and oils, making it suitable for applications requiring high chemical stability, such as medical devices and industrial protection; and its good light transmittance and clarity make it ideal for optical films and display devices. It plays an important role in fields such as protection; its environmentally friendly and non-toxic characteristics align with the current global advocacy of green manufacturing and sustainable development, making it safe and reliable for use in food packaging, children's products, and other fields; its easy processing and molding features allow it to be manufactured into products of different shapes and specifications through various processes such as injection molding, extrusion, and blow molding, greatly reducing production difficulty and costs; in addition, its excellent tear and puncture resistance makes it indispensable in fields requiring high-strength protection, such as sports equipment and military equipment; its excellent resilience ensures performance stability during long-term use; its good electrical insulation properties make it play an important role in the field of electronics and electrical appliances; and its recyclable and reusable characteristics further enhance its environmental and economic value. With these comprehensive advantages, TPU film is used in a wide range of fields, from everyday consumer goods to high-end industrial products. In the apparel and footwear industry, it is used to make waterproof and breathable jacket fabrics and highly elastic sports shoe uppers. In the medical field, it is used to produce soft and comfortable infusion bags and biocompatible medical catheters. In the automotive industry, it is used to manufacture wear-resistant and weather-resistant interior materials and seals. In the electronics field, it is used to make high-performance protective mobile phone cases and high-insulation cable sheaths. In the packaging field, it is used to produce biodegradable and environmentally friendly packaging bags.

[0003] Currently, TPU film color designs have reached a wide variety of types, including multi-color, monochrome, and dazzling colors, which can meet the personalized appearance needs of different customers. However, to achieve complex and artistic effects such as multi-color, mixed colors, and flow patterns on the same TPU film, in most cases, it is still necessary to rely on secondary processing methods such as digital printing and ink printing. These secondary processing techniques have significant drawbacks in actual operation. Taking digital printing as an example, the process involves multiple cumbersome steps, including film pretreatment, pattern design output, inkjet printing, color fixing, and post-processing. Each step requires precise control of process parameters such as temperature, humidity, and pressure, placing extremely high demands on equipment precision and operator skill. If any step deviates, it can lead to problems such as distorted pattern colors and blurred edges, resulting in low production efficiency and a significant increase in the complexity of the entire process. From a cost perspective, the high purchase cost of digital printing equipment, the high cost of special inks, and the large amount of labor input all contribute to increasing the cost of multi-color processing of TPU films, severely compressing the profit margins of enterprises. Moreover, the solvents used in the ink printing process may pose potential hazards to the environment and human health. More importantly, the multi-color effects obtained through secondary processing do not perform well in terms of weather resistance. Long-term exposure to natural environments such as sunlight, rain, and temperature changes can easily cause the ink to fade and peel off, resulting in the loss of the original aesthetics and integrity of the pattern on the film surface, which cannot meet the needs of outdoor products, automotive decorations, and other applications with high weather resistance requirements. Although CN112895512A discloses a single-color TPU casting process that achieves stable production of single-color TPU films by controlling parameters such as temperature and speed during melt casting, this process encounters difficulties when co-extruding multi-color masterbatches. The differences in melt viscosity and flowability between different color masterbatches make uniform mixing during extrusion difficult, leading to disordered flow lines, uneven color distribution, and chaotic textures, failing to achieve the desired multi-color flow line effect. JP2019052017A addresses the adhesive's water resistance issue by using PCDI (polycarbonate diisocyanate) as a modifier. By improving the molecular structure of adhesives, their bonding performance in humid environments has been enhanced. However, this technology only focuses on optimizing the performance of adhesives and does not involve the effective control of melt rheological behavior. The rheological characteristics of the melt during the extrusion process, such as shear rate and stress distribution, directly affect the mixing uniformity of multicolor masterbatches and the flow pattern forming effect. Without the control of this key factor, it is impossible to solve the problem of turbulent diffusion during one-time forming of multicolor flow patterns. When multiple colors of melt flow in the mold channel, turbulence will cause uneven color diffusion, forming irregular color spots or stripes, which seriously affects the appearance quality and performance of the film.Therefore, the industry still faces bottlenecks in one-time molding technology for multi-color flow patterns. How to achieve precise control of melt rheological behavior by optimizing melt formulation, improving extrusion equipment structure, or adjusting processing parameters, thereby effectively suppressing turbulent diffusion and obtaining a uniform and beautiful multi-color flow pattern effect, has become a key technical problem that urgently needs to be solved. Solving this problem will greatly promote the application of TPU film in high-end decoration, functional composite materials and other fields, and improve the overall technical level and market competitiveness of the industry. Summary of the Invention

[0004] TPU film, a high-performance functional material, is produced by processing thermoplastic polyurethane elastomer (TPU) granules through a series of precise and targeted special processes, including calendering, casting, blown film production, and coating. These processes precisely control the film's thickness, structure, and properties according to different application requirements. TPU's unique molecular structure consists of both hard and soft segments. The hard segments, with their rigid, orderly arrangement, act like the material's "skeleton," giving TPU excellent tensile strength, making it less prone to breakage under tensile stress. They also provide excellent wear resistance, maintaining the integrity of the material surface even after prolonged friction, and grant TPU a certain degree of heat resistance, allowing for stable use in high-temperature environments. The soft segments, composed of flexible segments, act like "elastic springs" within the material. Through the free rotation and deformation between segments, TPU possesses rubber-like elasticity, enabling it to quickly return to its original shape after deformation. This combination of rigidity and flexibility in its molecular structure gives TPU films a multitude of excellent properties: its superior elasticity and flexibility allow it to adapt to various complex bending, folding, and other dynamic deformation scenarios, making it stand out in fields requiring frequent movement, such as footwear and clothing; its strong weather resistance means it can withstand long-term erosion from natural environmental factors such as ultraviolet rays, rain, and extreme temperatures, resulting in a service life far exceeding that of ordinary materials when used in outdoor products and automotive parts; its chemical corrosion resistance gives it excellent resistance to various chemicals such as acids, alkalis, and oils, making it suitable for applications requiring high chemical stability, such as medical devices and industrial protection; and its good light transmittance and clarity make it ideal for optical films and display devices. It plays an important role in fields such as protection; its environmentally friendly and non-toxic characteristics align with the current global advocacy of green manufacturing and sustainable development, making it safe and reliable for use in food packaging, children's products, and other fields; its easy processing and molding features allow it to be manufactured into products of different shapes and specifications through various processes such as injection molding, extrusion, and blow molding, greatly reducing production difficulty and costs; in addition, its excellent tear and puncture resistance makes it indispensable in fields requiring high-strength protection, such as sports equipment and military equipment; its excellent resilience ensures performance stability during long-term use; its good electrical insulation properties make it play an important role in the field of electronics and electrical appliances; and its recyclable and reusable characteristics further enhance its environmental and economic value. With these comprehensive advantages, TPU film is used in a wide range of fields, from everyday consumer goods to high-end industrial products. In the apparel and footwear industry, it is used to make waterproof and breathable jacket fabrics and highly elastic sports shoe uppers. In the medical field, it is used to produce soft and comfortable infusion bags and biocompatible medical catheters. In the automotive industry, it is used to manufacture wear-resistant and weather-resistant interior materials and seals. In the electronics field, it is used to make high-performance protective mobile phone cases and high-insulation cable sheaths. In the packaging field, it is used to produce biodegradable and environmentally friendly packaging bags.

[0005] Currently, TPU film color designs have reached a wide variety of types, including multi-color, monochrome, and dazzling colors, which can meet the personalized appearance needs of different customers. However, to achieve complex and artistic effects such as multi-color, mixed colors, and flow patterns on the same TPU film, in most cases, it is still necessary to rely on secondary processing methods such as digital printing and ink printing. These secondary processing techniques have significant drawbacks in actual operation. Taking digital printing as an example, the process involves multiple cumbersome steps, including film pretreatment, pattern design output, inkjet printing, color fixing, and post-processing. Each step requires precise control of process parameters such as temperature, humidity, and pressure, placing extremely high demands on equipment precision and operator skill. If any step deviates, it can lead to problems such as distorted pattern colors and blurred edges, resulting in low production efficiency and a significant increase in the complexity of the entire process. From a cost perspective, the high purchase cost of digital printing equipment, the high cost of special inks, and the large amount of labor input all contribute to increasing the cost of multi-color processing of TPU films, severely compressing the profit margins of enterprises. Moreover, the solvents used in the ink printing process may pose potential hazards to the environment and human health. More importantly, the multi-color effects obtained through secondary processing do not perform well in terms of weather resistance. Long-term exposure to natural environments such as sunlight, rain, and temperature changes can easily cause the ink to fade and peel off, resulting in the loss of the original aesthetics and integrity of the pattern on the film surface, which cannot meet the needs of outdoor products, automotive decorations, and other applications with high weather resistance requirements. Although CN112895512A discloses a single-color TPU casting process that achieves stable production of single-color TPU films by controlling parameters such as temperature and speed during melt casting, this process encounters difficulties when co-extruding multi-color masterbatches. The differences in melt viscosity and flowability between different color masterbatches make uniform mixing during extrusion difficult, leading to disordered flow lines, uneven color distribution, and chaotic textures, failing to achieve the desired multi-color flow line effect. JP2019052017A addresses the adhesive's water resistance issue by using PCDI (polycarbonate diisocyanate) as a modifier. By improving the molecular structure of adhesives, their bonding performance in humid environments has been enhanced. However, this technology only focuses on optimizing the performance of adhesives and does not involve the effective control of melt rheological behavior. The rheological characteristics of the melt during the extrusion process, such as shear rate and stress distribution, directly affect the mixing uniformity of multicolor masterbatches and the flow pattern forming effect. Without the control of this key factor, it is impossible to solve the problem of turbulent diffusion during one-time forming of multicolor flow patterns. When multiple colors of melt flow in the mold channel, turbulence will cause uneven color diffusion, forming irregular color spots or stripes, which seriously affects the appearance quality and performance of the film.Therefore, the industry still faces bottlenecks in one-time molding technology for multi-color flow patterns. How to achieve precise control of melt rheological behavior by optimizing melt formulation, improving extrusion equipment structure, or adjusting processing parameters, thereby effectively suppressing turbulent diffusion and obtaining a uniform and beautiful multi-color flow pattern effect, has become a key technical problem that urgently needs to be solved. Solving this problem will greatly promote the application of TPU film in high-end decoration, functional composite materials and other fields, and improve the overall technical level and market competitiveness of the industry.

[0006] Table 1 Product Parameters for Example 0

[0007] Comparative Example A (Difference from Example 0) Filter mesh count = 100 mesh Comparative Example B (differences from Example 0) Die head temperature = 160℃ Comparative Example C (differences from Example 0) Blue / Red Masterbatch Mass Ratio = 1:3

[0008] Example 1

[0009] Step 1: Preparation of multi-color flow pattern masterbatch TPU masterbatch in natural color: 25 parts TPU flow-pattern blue masterbatch: 3 parts TPU flow pattern red masterbatch: 3 parts (blue:red mass ratio = 1:1) Antioxidant (Type 1010): 1 part UV-resistant additive (UV-531): 1 part Mixing method: High-speed mixer, 1200 rpm, 15 minutes Step 2: Casting process settings Screw temperature: 200℃ (Zone I), 205℃ (Zone II), 210℃ (Zone III) Die head temperature: 195℃ (temperature difference ≤ 10℃) Laminating roller temperature: 160℃ Laminating roller pressure: 45 Kgf Filter mesh size: 150 mesh Step 3: Preparation of adhesive layer Polyurethane adhesive resin: 85 parts Antioxidant: 1 part Water-resistant agent (Stabaxol P200): 0.5 parts Polycarbodiimide crosslinking agent (PCDI, molecular weight 3500 g / mol): 3 parts Nano-sized boron nitride (particle size 80 nm, specific surface area 220 m² / g): 0.8 parts Mixing method: Ultrasonic dispersion for 30 minutes + mechanical stirring at 2000 rpm for 20 minutes Coating method: Slit coating head, coating amount 15 g / m² Step 4: Lamination and Drying Composite temperature: 140℃ Drying gradient: 80℃ (10 min) → 120℃ (15 min) → 80℃ (10 min) Composite pressure: 0.5 MPa Step 5: Maturation and peeling Curing conditions: 25℃ / RH60%, 48 hours Peeling speed: 5 m / min

[0010] Example 2

[0011] Step 1: Masterbatch Preparation TPU masterbatch in natural color: 10 parts TPU flow pattern blue masterbatch: 0.5 parts Antioxidant: 0.5 parts UV-resistant additive: 0.1 parts Step 2: Casting process Screw temperature: 170℃ (uniform) Die head temperature: 170℃ (temperature difference 0℃) Laminating roller temperature: 140℃ Laminating roller pressure: 30 Kgf Step 3: Adhesive layer Polyurethane adhesive resin: 70 parts PCDI: 0.5 parts Nano boron nitride: 0.1 parts (mass ratio 5:1) Step 4: Drying Gradient: 40℃ (20 min) → 80℃ (20 min) → 40℃ (20 min)

[0012] Example 3

[0013] Step 1: Masterbatch Preparation TPU masterbatch in natural color: 30 parts TPU flow pattern red masterbatch: 6 parts Antioxidant: 3 parts UV protection additive: 3 parts Step 2: Casting process Screw temperature: 220℃ (uniform) Die head temperature: 220℃ (temperature difference 0℃) Laminating roller temperature: 200℃ Laminating roller pressure: 60 Kgf Step 3: Adhesive layer Polyurethane adhesive resin: 100 parts PCDI: 5 copies Nano boron nitride: 1 part (mass ratio 5:1) Step 4: Drying Gradient: 100℃ (10 min) → 160℃ (10 min) → 100℃ (10 min) Comparative Example 1 (Difference from Example 1: No PCDI / boron nitride) Step 3 Changes: Remove PCDI and boron nitride Other aspects are the same as in Example 1. Comparative Example 2 (Difference from Example 1: PCDI only) Step 3 Changes: Add PCDI: 3 copies Remove boron nitride Other aspects are the same as in Example 1. Comparative Example 3 (Difference from Example 1: only boron nitride) Step 3 Changes: Added boron nitride: 0.8 parts Remove PCDI Other aspects are the same as in Example 1. Comparative Example 4 (Difference from Example 1: Boron nitride is replaced with titanium dioxide) Step 3 Changes: Add PCDI: 3 copies Replace with titanium dioxide (particle size 100nm): 0.8 parts Other aspects are the same as in Example 1. Comparative Example 5 (Difference from Example 1: Imbalanced proportions) Step 3 Changes: Add PCDI: 1 copy Add boron nitride: 1 part (mass ratio 1:1) Other aspects are the same as in Example 1. The obtained products were tested according to the following standards, and the results are shown in Table 1.

[0014] ① ΔE: ISO 2919 "Determination of color difference in plastics" ② Color difference transition zone: GB / T 30776-2014 "Microscopic Image Analysis of Plastics" ③ Bending resistance: ASTM D2176 "Test for Flexural Resistance of Elastic Materials"

[0015] The technical solution claimed in claim 1 of this invention achieves multi-color flow pattern one-time molding (ΔE≤3.5) for the first time through the synergistic effect of filter mesh number (200 mesh), die temperature (195℃), and blue-red ratio (1:1), breaking through the technical prejudice of "requiring secondary processing". PCDI forms a cross-linked network to lock the color master particles and inhibit diffusion; nano-boron nitride directionally shears the melt and guides the flow pattern to arrange in an orderly manner; the ratio of the two is specific: the interfacial energy is minimal at 3.75:1; this invention produces unexpected technical effects (ΔE≤2 vs Example 03.2) through PCDI / boron nitride at a ratio of (3-5):1, and cannot be achieved by a single component or simple substitution (comparative examples 4-5 verify the material specificity).

[0016] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0017] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention. Attached Figure Description Figure 1 The flowchart for the preparation of multicolor flow-textured TPU film provided by the present invention.

Claims

1. A method for preparing a multi-color flow-textured TPU film, characterized in that: Includes the following steps: (1) Multicolor flow pattern masterbatch preparation: mix TPU natural color masterbatch, at least one colored flow pattern masterbatch, antioxidant and anti-UV additive; (2) Casting process settings: Adjust screw temperature, die temperature, bonding roller temperature and bonding roller pressure; (3) Preparation of adhesive layer: Polyurethane adhesive resin, antioxidant, water-resistant agent, polycarbodiimide crosslinking agent and nano boron nitride are mixed and coated; (4) Composite and drying: The adhesive layer of step (3) is composited with the masterbatch extrusion substrate of step (1) and then dried in a gradient. (5) Mature peeling to produce multi-colored flow pattern TPU film.

2. The method as described in claim 1, characterized in that: The proportions of each group in step (1) are as follows: 10-30 parts of TPU natural color masterbatch, 0.5-6 parts of colored flow pattern masterbatch, 0.5-3 parts of antioxidant, and 0.1-3 parts of anti-UV additive.

3. The method as described in claim 1 or 2, characterized in that: The colored flow pattern masterbatch comprises blue flow pattern masterbatch and red flow pattern masterbatch, and the mass ratio of the two is 1:(0.8-1.2).

4. The method as described in claim 1, characterized in that: In step (2): The screw temperature is 170-220℃, and the die head temperature is 170-220℃. The temperature difference between the die head and the screw should be ≤10℃. The laminating roller temperature is 140-200℃, and the laminating roller pressure is 30-60Kgf.

5. The method as described in claim 1, characterized in that: The proportions of each group in step (3) are as follows: 70-100 parts of polyurethane adhesive resin, 0.5-3 parts of antioxidant, 0.03-1.5 parts of water resistant agent, 0.5-5 parts of polycarbodiimide crosslinking agent, and 0.1-1 parts of nano boron nitride.

6. The method as described in claim 5, characterized in that: The polycarbodiimide crosslinking agent is an aromatic polycarbodiimide with a molecular weight of 2000-5000 g / mol; the nano boron nitride has a particle size of 50-100 nm and a specific surface area of ​​≥200 m² / g.

7. The method as described in claim 5, characterized in that: The mass ratio of polycarbodiimide crosslinking agent to nano boron nitride is (3-5):

1.

8. The method as described in claim 1, characterized in that: In step (4), the gradient drying adopts a temperature increase and then decrease method, with a drying temperature of 40-160℃.

9. A multi-color flow-textured TPU film, characterized in that: Prepared by any one of claims 1-8, its surface has a multi-color mixed flow pattern effect, the flow pattern width is 0.1-0.5 mm, and the flow pattern spacing is 0.3-1.0 mm; The clarity of the flow pattern ΔE ≤ 1.5, and the number of folding cycles ≥ 500,000; The total thickness of the film is 0.2-0.8mm, and the surface has a pearlescent or gradient color effect; The flow pattern contains at least two colors, with no obvious diffusion at the color boundaries and a color difference transition zone width ≤ 50 μm.

10. The application of the multicolor flow-textured TPU film of claim 9 in the preparation of sports shoe uppers, electronic product protective cases or outdoor equipment components.

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