Semi-shading type double-color TPU (thermoplastic polyurethane) film as well as preparation method and application thereof

Abstract

The invention relates to the field of thin film materials, in particular to a semi-shading type double-color TPU thin film, a preparation method and application. The semi-shading type double-color TPU film comprises at least one light-transmitting area and a shading developing area, is prepared from thermoplastic polyurethane (TPU) resin, shading filler, color master batch, an interface compatilizer and a functional aid according to a certain weight percentage, has the thickness of 0.05-0.5 mm, and is of an integrated structure by co-extrusion molding of the light-transmitting area and the shading developing area; the preparation method comprises the following steps: respectively preparing materials, adding the materials into an extruder of a double-material-channel co-extrusion system, controlling the temperature to extrude and form a film, cooling and rolling, and arranging a'dovetail joint '-shaped interlocking structure in a partitioned runner in a co-extrusion die head. The invention further relates to application of the film in the aspects of automotive trim shading pads and the like. The preparation method has the technical effects that the TPU film which has semi-shading and double-color effects, good performance of a light-transmitting area and a shading color development area and high interface bonding strength is prepared, and the TPU film can be applied to multiple fields.

Description

Technical Field

[0001] This application relates to the field of polymer film materials, and in particular to a semi-opaque dual-color TPU film, its preparation method, and its application. Background Technology

[0002] Thermoplastic polyurethane (TPU) films are widely used in clothing, footwear, electronics, automotive, and medical fields due to their excellent flexibility, abrasion resistance, high elasticity, and good processing performance. With the upgrading of consumption and the increasing demands for product design aesthetics, the market demand for polymer films with complex visual effects and functional integration is growing. For example, in automotive interiors, it is often necessary to integrate translucent logos or light strips into sunshades; in sports protective gear, it is necessary to have both the internal structure visible (translucent area) and a cool colored border (sunshade area).

[0003] Currently, the traditional method to achieve this effect mainly involves post-processing lamination, such as bonding a transparent TPU film to an opaque colored film using adhesives, or selectively printing light-blocking inks onto a transparent film. In addition, existing technologies also include multi-layer film production through co-extrusion, but these methods primarily focus on the superposition of barrier or mechanical properties.

[0004] These methods have many drawbacks: the post-composite processing is cumbersome and costly; the bonding interface is easily peeled off, resulting in poor durability; the printed layer is prone to wear and peeling, and has an unpleasant feel; and they are not environmentally friendly (using solvent-based adhesives or inks). There is limited research on multi-layer co-extrusion for achieving clear partitioning of "light-transmitting" and "colored light-blocking" integrated molding within the same plane. The main technical challenges lie in the significant difference in rheological behavior between the light-transmitting formulation and the highly filled light-blocking formulation, which can easily lead to interface instability, blurring, or extrusion cracking during co-extrusion; weak interfacial bonding between the two phases, making delamination during use; and the introduction of light-blocking fillers can severely impair the inherent flexibility and tensile properties of TPU. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a semi-opaque dual-color TPU film, its preparation method, and its applications. This film, through a unique formulation design and innovative co-extrusion process, successfully achieves integrated molding of the light-transmitting area and the light-blocking color-developing area, solving the technical challenges of interface fusion and performance balance.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A semi-opaque dual-color TPU film, the film comprising at least one light-transmitting area and one light-opaque color-developing area; the film is composed of the following components by weight percentage:

[0008] Thermoplastic polyurethane (TPU) resin: 70-85%;

[0009] Light-shielding filler: 10-25%;

[0010] Masterbatch: 2-8%;

[0011] Interface compatibilizer: 1-3%;

[0012] Functional additives: 1-4%.

[0013] By adopting the above technical solution, the film can achieve clear partitioning of "light transmission" and "colored light blocking" in the same plane, which solves the problem of interface instability when co-extruding light transmission formula and high-filler light blocking formula. It enhances the interfacial bonding force between the two phases, reduces the damage of light blocking filler to the inherent flexibility and tensile properties of TPU, and gives the film excellent mechanical properties, weather resistance and color stability, meeting the requirements of integrated design and aesthetic function.

[0014] Preferably, the light-shielding filler is a mixture of rutile titanium dioxide and barium sulfate in a weight ratio of (1:1) to (1:3) and has an average particle size of 0.2-0.8 μm.

[0015] By adopting the above technical solution, the film includes a light-transmitting area and a light-shielding and color-developing area, and is composed of thermoplastic polyurethane resin, light-shielding filler, color masterbatch, interface compatibilizer and functional additives in a specific ratio. The light-shielding filler is made of rutile titanium dioxide and barium sulfate in a weight ratio of (1:1) to (1:3) with an average particle size of 0.2-0.8μm, which can achieve a balance between light shielding and mechanical properties. When the total filler content in the light-shielding area is in the range of 20-25%, the light shielding rate can reach an excellent level. Increasing the proportion of barium sulfate is beneficial to maintaining flexibility.

[0016] Preferably, the color masterbatch is a high-concentration coloring masterbatch based on a polyurethane carrier, with a pigment content of ≥40%, and the color of the color masterbatch is selected from black, gray, blue or red.

[0017] By adopting the above technical solution, the color masterbatch uses polyurethane as a carrier and has a pigment content of ≥40%, which can provide high-concentration coloring. Combined with black, gray, blue or red, it can make the light-shielding color display area of ​​the semi-opacified dual-color TPU film present a specific color. The color masterbatch can also contribute part of the light-shielding effect and work synergistically with the light-shielding filler to improve the light-shielding performance of the film.

[0018] Preferably, the interface compatibilizer is maleic anhydride-grafted thermoplastic polyurethane or an oxazoline-based compatibilizer.

[0019] By adopting the above technical solution and using maleic anhydride-grafted thermoplastic polyurethane or oxazoline compatibilizer as interface compatibilizer, the interfacial bonding strength between the light-transmitting area and the light-shielding color-developing area of ​​the film can be improved, avoiding unstable interface and weak bonding, making the interface peel strength ≥20 N / cm, and ensuring the visual clarity of the interface, thus solving the problems of easy peeling and poor durability of the bonding interface in traditional methods.

[0020] Preferably, the functional additives include at least one of UV stabilizers, antioxidants, and hydrolysis inhibitors.

[0021] By adopting the above technical solution, the semi-opaque dual-color TPU film includes a light-transmitting area and a light-blocking color-developing area, and is composed of thermoplastic polyurethane resin, light-blocking filler, color masterbatch, interface compatibilizer and functional additives in a specific ratio. At the same time, the functional additives are selected from at least one of UV stabilizers, antioxidants and hydrolysis stabilizers, which can absorb ultraviolet rays to prevent photoaging, prevent thermo-oxidative degradation to improve thermal stability, inhibit polyurethane hydrolysis reaction to extend film life, thereby giving the film excellent weather resistance and a longer service life.

[0022] Preferably, the visible light transmittance of the light-transmitting area is 40%-70%, and the haze is ≤15%; the visible light shading rate of the light-shielding color-developing area is ≥90%, and the interface peel strength between the light-transmitting area and the light-transmitting area is ≥20 N / cm.

[0023] By adopting the above technical solution, the light-transmitting area of ​​the film has a visible light transmittance of 40%-70% and a haze of no more than 15%, which can meet the light transmission design requirements; at the same time, the visible light shading rate of the light-shielding and color-developing area reaches more than 90%, which can achieve a good shading effect; and the interface peel strength between the light-shielding and color-developing area and the light-transmitting area is not less than 20 N / cm, ensuring that the interface between the two areas is firmly bonded.

[0024] Preferably, the thickness of the film is 0.05-0.5 mm, and the light-transmitting area and the light-blocking color-developing area are formed into an integrated structure through co-extrusion molding.

[0025] By adopting the above technical solutions, the film has a suitable thickness range, which can meet the needs of different application scenarios. The light-transmitting area and the light-blocking color-developing area are formed into an integrated structure through co-extrusion molding, which can solve the problems of cumbersome post-composite processing, high cost, easy peeling of the bonding interface, poor durability, easy wear and peeling of the printed layer, poor feel and poor environmental protection in traditional processes. It can also solve the technical problems of unstable interface, blurring or extrusion cracking when co-extruding light-transmitting formula and high-filler light-blocking formula, weak bonding force between the two phases and easy delamination, and light-blocking filler damaging the flexibility and tensile properties of TPU. It can achieve clear partitioning of "light transmission" and "colored light blocking" integrated molding, which meets the requirements of integrated design and aesthetic function.

[0026] A method for preparing a semi-opaque dual-color TPU film as described in any one of claims 1-7, comprising the following steps:

[0027] a) Prepare materials for the light-transmitting area and the light-blocking color-developing area separately: premix the respective formulation components and melt granulate;

[0028] b) The two types of granules are added separately to the two independent extruders of the dual-channel co-extrusion system;

[0029] c) Control the temperature of the two extruders at 170-200℃, and extrude and cast films synchronously through a co-extrusion die with partitioned flow channels;

[0030] d) Cool, stretch, and wind up the formed film.

[0031] By adopting the above technical solution, materials for the light-transmitting area and the light-blocking color-developing area are prepared and granulated separately, so that the materials in the two areas can be uniformly mixed. Adding the two granules to the independent extruder of the dual-channel co-extrusion system can achieve precise feeding. By controlling the extruder temperature and extruding and casting the film simultaneously through the partitioned flow channel co-extrusion die, it can be ensured that the two materials are extruded at the appropriate temperature, so as to achieve the integrated molding of the light-transmitting area and the light-blocking color-developing area. Cooling, drawing and winding the molded film can obtain a complete semi-opaque two-color TPU film, which solves the problems of cumbersome post-composite processing and easy peeling of the bonding interface in traditional methods. It realizes the one-time molding of semi-opaque two-color TPU film with clear and firm interface, and has good light transmittance, color performance and mechanical properties.

[0032] Preferably, in step c), the partitioned flow channel in the co-extrusion die head is provided with a dovetail tenon-type interlocking structure to enhance the mechanical interlocking and fusion of the materials in the two zones at the interface.

[0033] By adopting the above technical solution, when preparing semi-opaque dual-color TPU film, the "dovetail" type interlocking structure is set in the partitioned flow channel inside the co-extrusion die head, which can enhance the mechanical interlocking and fusion of the light-transmitting material and the light-blocking color-developing material at the interface, making the interface between the light-transmitting area and the light-blocking color-developing area of ​​the film more firmly bonded and improving the overall performance of the film.

[0034] Application of a semi-opaque dual-color TPU film as described in any one of claims 1-7 in automotive interior sunshade mats, sports protective gear window components, smart watch straps, or high-end cosmetic packaging.

[0035] By adopting the above technical solution, semi-opaque dual-color TPU film can be used for automotive interior sunshade pads, sports protective gear window components, smart watch straps, or high-end cosmetic packaging. The film has both high light transmittance areas and specific color high opacity areas on the same film, and the interface between the two areas is clear and firmly bonded. It has excellent mechanical properties, weather resistance, and color stability, and can meet the integrated design and aesthetic function requirements of these application scenarios.

[0036] In summary, this application includes at least one of the following beneficial technical effects:

[0037] 1. Through formula optimization and special co-extrusion process, it is possible to simultaneously have high light transmittance areas and specific color high light shading areas on the same film, and the interface between the two areas is clear and firmly bonded, which solves the problems of easy peeling of the bonding interface and unstable interface of multi-layer co-extrusion in traditional methods.

[0038] 2. The film has excellent mechanical properties, weather resistance and color stability, avoiding the serious damage to the inherent flexibility and tensile properties of TPU caused by the introduction of light-blocking fillers;

[0039] 3. The dual-channel co-extrusion system and specially designed die head are used for preparation, which can form in one step, simplifying the processing flow, reducing costs, and solving the problems of cumbersome and costly post-processing composite processes in traditional manufacturing. Detailed Implementation

[0040] The present invention will be described in detail below through specific embodiments and comparative examples, but the scope of protection of the present invention is not limited thereto.

[0041] I. Experimental Materials

[0042] TPU resin: Grade 1185A (Shore hardness 85A), BASF, Germany;

[0043] Light-shielding fillers: rutile titanium dioxide (TiO2), average particle size 0.3 μm; precipitated barium sulfate (BaSO4), average particle size 0.5 μm;

[0044] Masterbatch: Polyurethane carrier, pigment content 50%, colors include black, gray, blue and red;

[0045] Interface compatibilizer: maleic anhydride-grafted TPU (MAH-g-TPU), grafting rate 0.8-1.2%;

[0046] Functional additives: UV stabilizer UV-234, antioxidant Irganox 1010, hydrolysis inhibitor Stabaxol P.

[0047] II. Preparation Process

[0048] Weigh each raw material component in the light-transmitting area and the light-blocking color-developing area separately, and mix them in a high-speed mixer for 3-5 minutes;

[0049] The mixture is added separately to a twin-screw extruder, melt-blended and extruded at 170-190℃;

[0050] The two types of granules were respectively added to two single-screw extruders, A and B, in a dual-channel co-extrusion system;

[0051] Set the temperature of extruder A (material in the light-transmitting zone) to 175-180℃ and the temperature of extruder B (material in the light-shielding zone) to 180-185℃.

[0052] The material is extruded synchronously through a co-extrusion die with a dovetail-shaped interlocking flow channel and cooled and shaped by a three-roll cooling casting machine;

[0053] The process involves traction, edge trimming, and winding to obtain a semi-opaque, two-color TPU film with a thickness of 0.2 mm.

[0054] III. Experimental Formula

[0055] Example formulations (1-10) Components Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 TPU resin (transparent area) 98 96 97 95 97 94 98 96 97 95 TPU resin (light-shielding area) 73 70 75 68 72 66 74 71 76 69 <![CDATA[TiO2 (Transparent Region)]]> 0 0.7 0 1 0 1.5 0 0.5 0 1.2 <![CDATA[TiO2 (light-shielding area)]]> 6.7 11 4.5 10 8.3 12.5 7.5 9 5 11.3 <![CDATA[BaSO4 (translucent region)]]> 0 1.3 0 2 0 2.5 0 1.5 0 1.8 <![CDATA[BaSO4 (Light-shielding area)]]> 13.3 11 13.5 10 11.7 12.5 12.5 9 15 11.3 Black masterbatch (transparent area) 0 0 0 0 0 0 0 0 0 0 Black masterbatch (light-shielding area) 5 6 5 5 5 7 4 5 2 5 Gray masterbatch (transparent area) 0 0 0 0 0 0 0 0 0 0 Gray masterbatch (light-shielding area) 0 0 0 0 0 0 0 0 0 0 Blue masterbatch (transparent area) 0 0 0 0 0 0 0 0 0 0 Blue masterbatch (light-shielding area) 0 0 0 0 0 0 0 0 0 0 Red masterbatch (transparent area) 0 0 0 0 0 0 0 0 0 0 Red masterbatch (light-shielding area) 0 0 0 0 0 0 0 0 0 0 Interface compatibilizer (transparent area) 1 1 2 1 1 1 1 1 2 1 Interface compatibilizer (light-shielding area) 1 1 1 1 1 1 1 1 1 1 Functional additive package (transparent area) 1 1 1 1 1 1 1 1 1 1 Functional additive pack (light-shielding area) 1 1 1 1 1 1 1 1 1 1

[0056] IV. Comparative Experimental Design

[0057] Comparative formulations (1-6) Components Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 TPU resin (transparent area) 98 85 98 97 98 97 TPU resin (light-shielding area) 82 - 88 90 65 73 <![CDATA[TiO2 (Transparent Region)]]> 0 3.3 0 0 0 0 <![CDATA[TiO2 (light-shielding area)]]> 4 - 2 1 8.3 6.7 <![CDATA[BaSO4 (translucent area)]]> 0 6.7 0 0 0 0 <![CDATA[BaSO4 (Light-shielding area)]]> 8 - 4 2 16.7 13.3 Black masterbatch (transparent area) 0 3 0 0 0 0 Black masterbatch (light-shielding area) 4 - 4 5 5 5 Interface compatibilizer (transparent area) 1 1 0 1 1 1 Interface compatibilizer (light-shielding area) 1 - 0 1 1 1 Functional additive package (transparent area) 1 1 1 1 1 1 Functional additive pack (light-shielding area) 1 - 1 1 1 1

[0058] *Note: Comparative Example 2 uses a single formulation and does not distinguish between light-transmitting and light-blocking areas; "-" indicates that this option is not available.*

[0059] V. Performance Test Results

[0060] Performance test results of the examples (1-10) Test Project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Light transmittance (%) of the light-transmitting area 65 55 70 48 68 42 72 58 69 50 Haze in the light-transmitting area (%) 10 12 8 18 9 22 7 14 8 20 Shading rate of shaded area (%) 95 98 93 99 96 99.5 94 97 92 98.5 Interfacial peel strength (N / cm) 28 25 30 22 26 20 29 24 32 21 Film breaking elongation (%) 450 420 480 380 460 350 490 410 500 370 L* value (blackness) of the shaded area 25 20 28 18 26 15 30 22 35 17 Interface visual clarity Clear Clear Clear Clearer Clear Clearer Clear Clear Clear Clearer

[0061] Comparative performance test results (1-6) Test Project Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Light transmittance (%) of the light-transmitting area 68 32 66 70 62 64 Haze in the light-transmitting area (%) 9 60 11 8 15 10 Shading rate of shaded area (%) 85 88 75 65 96 95 Interfacial peel strength (N / cm) 15 - 8 18 12 27 Film breaking elongation (%) 400 350 500 520 320 440 L* value (blackness) of the shaded area 35 40 38 45 24 26 Interface visual clarity Vague No interface Severe blur Vague Clear Clear

[0062] Composition of functional adjuvant package (by weight percentage, based on total weight of functional adjuvant package) Types of adjuvants Content (wt%) Specific brand / specification Main functions UV protectant 30 UV-234 (BASF) Absorbs ultraviolet rays and prevents photoaging. antioxidants 50 Irganox 1010 (BASF) Prevents thermo-oxidative degradation and improves thermal stability Anti-hydrolysis agent 20 Stabaxol P (Rhein Chemicals) Inhibits polyurethane hydrolysis and extends its lifespan.

[0063] Test Method Description Table

[0064] Table 6: Performance Testing Methods and Standards Test Project Test Standards Brief description of test equipment / methods Light transmittance ASTM D1003 A haze meter was used to measure the transmittance of light at a wavelength of 550 nm. Haze ASTM D1003 Use a haze meter to measure the proportion of scattered light to total transmitted light. shading rate Calculated value Opacity (%) = (1 - Transmittance / 100) × 100 interfacial peel strength ASTM D1876 (T-type peel) Using a universal testing machine, the tensile speed was 100 mm / min. Film breaking elongation ASTM D638 Using a universal testing machine, the tensile speed was 500 mm / min. L* value (blackness) of the shaded area CIE L*a*b* Color Space Using a spectrophotometer, a D65 light source, and a 10° observation angle. Interface visual clarity Visual evaluation Three people gave independent evaluations, and the majority opinion was taken, resulting in four levels.

[0065] *Note: The shading rate is calculated as (1 - transmittance) * 100%; the lower the L value, the darker the color; the subjective evaluation of interface clarity is divided into four levels: "clear", "relatively clear", "blurry" and "severely blurry".

[0066] VI. Data Analysis and Discussion

[0067] The following analysis, combining formulation and test data, details the impact of various factors on film performance:

[0068] 1. Impact Analysis of the Light-Shielding Filler System

[0069] The light-shielding filler (TiO2 / BaSO4) is the core factor determining the performance of the light-shielding zone. As seen in Examples 1, 3, 5, 7, and 9, when the total filler content in the light-shielding zone is in the range of 20-25% (TiO2:BaSO4 approximately 1:2), the light-shielding rate reaches an excellent level of 93-96% (e.g., Example 1: 95%, Example 5: 96%). In Comparative Example 1, the total filler content is only 12%, resulting in a light-shielding rate of only 85%; in Comparative Example 4, the total filler content is only 3%, resulting in a light-shielding rate as low as 65%, completely failing to meet the light-shielding requirements. This proves that a high filler content is a necessary condition for obtaining a high light-shielding rate.

[0070] The filler ratio also has an impact: Example 9 uses a 1:3 TiO2 / BaSO4 ratio (20% of total content), with a slightly lower shading rate of 92%, but a high elongation at break of 500%, indicating that increasing the BaSO4 ratio helps maintain flexibility, but at the cost of slightly sacrificing shading efficiency. Example 6 uses a 1:1 ratio with a high total content of 25%, achieving a shading rate of 99.5%, but the elongation at break drops to 350%, demonstrating the negative impact of the filler on mechanical properties. This invention achieves the optimal balance between shading and mechanical properties by optimizing a ratio of 1:1 to 1:2.

[0071] 2. The Influence of Masterbatch Type and Dosage

[0072] Examples 1-8 and 10 all used black masterbatch at a dosage of 4-7%. The L-value (blackness index) of the shading area shows that as the amount of masterbatch increases, the L-value decreases (the color becomes darker). Example 6 had the lowest L-value (15, the darkest) at a dosage of 7%, while Example 9 had the highest L-value (35, dark gray) at a dosage of only 2%. Masterbatch not only provides color but also contributes to the shading effect, especially dark-colored masterbatch.

[0073] Although Comparative Example 4 used less light-shielding filler, the light-shielding rate was only 65% ​​with a color masterbatch dosage of 5%, proving that high light-shielding cannot be achieved by relying solely on color masterbatch and must be combined with light-shielding filler.

[0074] 3. The influence of the design of the light-transmitting zone formula

[0075] There are three design strategies for the light-transmitting area: ① Completely transparent (e.g., Examples 1, 3, 5, 7, 9, without filler, light transmittance 65-72%, haze 7-10%); ② Semi-transparent milky white (e.g., Examples 2, 4, 6, 8, 10, with 1-3% filler added, light transmittance 42-58%, haze 12-22%). The latter uses a small amount of filler to scatter light, creating a soft visual effect and meeting different design requirements.

[0076] Comparative Example 2 used a single formulation to attempt to balance light transmission and shading. The results showed poor performance in the light transmission area (32% light transmittance, 60% haze) and insufficient performance in the shading area (88%), proving that a dual-formulation zoned design is necessary.

[0077] 4. The key role of interfacial compatibilizers

[0078] The interfacial compatibilizer (MAH-g-TPU) is crucial for interfacial bonding strength. All examples (1-10) with 1-2% compatibilizer added exhibited interfacial peel strength ≥20 N / cm. Examples 3 and 9, with 2% compatibilizer added to the light-transmitting region, achieved maximum interfacial strengths of 30 and 32 N / cm, respectively.

[0079] Comparative Example 3, with no compatibilizer added, exhibited an interfacial strength of only 8 N / cm despite a formulation similar to Example 1, and the interface was "severely blurred," indicating poor melt compatibility, leading to interfacial instability and weak bonding. Comparative Example 5, with a total filler content as high as 25% (TiO2:BaSO4=1:2), had an interfacial strength of only 12 N / cm. The reason for this was that the high filler content resulted in a much higher melt viscosity in the light-shielding region compared to the light-transmitting region, and the rheological mismatch weakened the interfacial bonding, which was difficult to fully compensate for even with a compatibilizer.

[0080] 5. Synergistic effect of process and formulation

[0081] Examples 1-10 all used co-extrusion dies with dovetail runners, and combined with appropriate formulations (filler content, compatibilizer), resulting in clear interfaces. Comparative Example 6 had a formulation almost identical to Example 1, but was co-extruded using a standard flat-seam die. While the interface strength (27 N / cm) was still acceptable, it was lower than that of Example 1 (28 N / cm) using a special die, demonstrating that the mechanical interlocking provided by the special die further enhances the interface.

[0082] Although Comparative Examples 1 and 4 used compatibilizers and co-extrusion processes, their interface clarity was rated as "fuzzy" either because of insufficient filler (small performance difference between the light-shielding and light-transmitting areas, resulting in an indistinct interface) or because of too little filler (too small performance difference between the two areas).

[0083] 6. Comprehensive Performance Evaluation

[0084] Examples 3 and 7 demonstrate optimal overall performance: clear light-transmitting areas (70-72% transmittance, 7-8% haze), excellent performance in the shading areas (93-94% shading), strongest interfacial bonding (30-29 N / cm), and superior mechanical properties (480-490% elongation). Their common characteristics include pure light-transmitting areas, moderate filler content in the shading areas (18-20%), and sufficient use of compatibilizer.

[0085] Example 6 represents a high shading application (shading rate 99.5%, L* value 15), suitable for occasions with extremely strict shading requirements, although its flexibility is reduced (elongation 350%).

[0086] This invention utilizes an independent dual-formulation system to specifically optimize the light-transmitting and light-blocking areas, and then firmly combines them through interface compatibility technology and a special co-extrusion process, successfully solving the problem of multifunctional integration that traditional methods cannot achieve.

[0087] in conclusion

[0088] The semi-opaque dual-color TPU film provided by this invention, through innovative zoned formulation design (especially the compounding and high-content use of opaque fillers and the introduction of interface compatibilizers) and a special co-extrusion molding process (dedicated die), successfully produces an integrated film with a clear and strong interface, possessing both high light transmittance and high opacity color rendering functions. This product boasts excellent performance, a simplified processing flow, and good environmental friendliness, and has broad application prospects in multiple fields such as automotive, consumer electronics, and sporting goods.

[0089] This application also provides a method for preparing a semi-opaque dual-color TPU film, including the following steps:

[0090] S1. Prepare materials for the light-transmitting zone and the light-blocking color-developing zone separately: Premix and melt-granulate the components of each formulation. First, accurately weigh the raw material components such as thermoplastic polyurethane (TPU) resin, light-blocking filler, color masterbatch, interface compatibilizer, and functional additives according to the different formulations for the light-transmitting and light-blocking color-developing zones. Then, place these raw materials in a high-speed mixer and mix for 3-5 minutes to ensure that the components are fully and evenly mixed. Next, add the mixture to a twin-screw extruder separately and melt-blend and extrude granulate at 170-190℃. During this process, it is important to control the extruder temperature and screw speed to ensure that the materials are fully melted and mixed to obtain uniform granules.

[0091] S2, the two types of granules are added separately to the two independent extruders of the dual-channel co-extrusion system. The dual-channel co-extrusion system can achieve separate conveying and extrusion of the material in the light-transmitting zone and the material in the light-blocking and color-developing zone. The prepared light-transmitting zone granules are added to extruder A, and the light-blocking and color-developing zone granules are added to extruder B, preparing for subsequent co-extrusion molding.

[0092] S3 controls the temperature of two extruders between 170-200℃, simultaneously extruding and casting the material through a co-extrusion die with partitioned flow channels. The temperature of extruder A (transparent zone material) is set at 175-180℃, and the temperature of extruder B (shadow zone material) is set at 180-185℃. The material is simultaneously extruded through the co-extrusion die with a dovetail-type interlocking flow channel. This dovetail-type interlocking structure enhances the mechanical interlocking and fusion of the two zones at the interface. The extruded material is then cooled and formed in a three-roll cooling casting machine to create a semi-shadow-proof, two-color TPU film.

[0093] S4 involves cooling, traction, and winding the formed film. The formed film requires thorough cooling to ensure its dimensional stability and performance. Then, the film is pulled to the appropriate position using a traction device, and finally wound up to obtain the finished semi-opaque two-color TPU film.

[0094] The implementation principle of this embodiment is as follows: by preparing materials for the light-transmitting area and the light-blocking color-developing area separately, the mutual interference between the two different formulations is avoided, ensuring the stability of the performance of each area. The use of a dual-channel co-extrusion system and a co-extrusion die enables the synchronous extrusion and integrated molding of the two materials, improving production efficiency. The dovetail interlocking structure enhances the interfacial bonding force between the two areas, solving problems such as interface instability and blurring in traditional co-extrusion processes. Temperature control and process parameter settings throughout the preparation process ensure the rheological properties and molding quality of the materials, ultimately producing an integrated film with a clear and firm interface, possessing both high light transmittance and high light-blocking color-developing functions. Compared with traditional post-processing composite methods, this method has advantages such as simple procedures, low cost, and good environmental friendliness.

[0095] This application also provides an application of a semi-opaque dual-color TPU film in automotive interior sunshade mats. In automotive interiors, it is often necessary to integrate translucent markings or light strips onto the sunshade mat. The translucent area of ​​the semi-opaque dual-color TPU film can be used to set translucent markings or light strips, achieving a clear display effect; the light-blocking and color-coding area can serve as the sun-blocking part, providing the necessary sun-blocking function. Its excellent mechanical properties and weather resistance ensure long-term use in the complex environment inside a car without problems such as interface peeling or wear. Moreover, this film is environmentally friendly, meeting the environmental requirements for automotive interior materials.

[0096] The implementation principle of this embodiment is as follows: the unique properties of the semi-opaque dual-color TPU film meet the needs of automotive interior sunshade pads for complex visual effects and functional integration. Its integrated structure avoids problems such as easy peeling of the bonding interface and poor durability caused by traditional post-processing lamination methods, thus improving product quality and reliability. At the same time, the film's high light transmittance, high opacity, and color rendering properties, as well as its good mechanical properties and weather resistance, enable it to be used stably in the high-temperature and high-light environments inside automobiles, providing a high-quality material choice for automotive interiors.

[0097] This application also provides an application of a semi-opaque dual-color TPU film in the viewing window component of sports protective gear. Sports protective gear needs to display both the internal structure (transparent area) and a stylish colored border (opaque area). The transparent area of ​​the semi-opaque dual-color TPU film allows the user to clearly see the internal structure of the protective gear, such as the movement of joints; the colored border of the opaque area enhances the aesthetics and style of the protective gear. Its excellent flexibility and abrasion resistance are suitable for the frequent use and friction of sports protective gear during exercise, and it will not be easily damaged.

[0098] The implementation principle of this embodiment is as follows: the characteristics of the semi-opaque dual-color TPU film are highly compatible with the requirements of the visual components of sports protective gear. The integrated design of the light-transmitting area and the light-blocking color-revealing area meets the dual requirements of the protective gear for light transmission and colored light blocking, while the flexibility and abrasion resistance of the film ensure the practicality and durability of the protective gear in sports scenarios. Compared with traditional post-processing or printing methods, the visual components made of this film are more durable and aesthetically pleasing, providing strong support for the design and performance improvement of sports protective gear.

[0099] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A semi-opaque dual-color TPU film, characterized in that, The film comprises at least one light-transmitting region and one light-blocking color-developing region; by weight percentage, the film is composed of the following components: Thermoplastic polyurethane (TPU) resin: 70-85%; Light-shielding filler: 10-25%; Masterbatch: 2-8%; Interface compatibilizer: 1-3%; Functional additives: 1-4%.

2. The semi-opaque dual-color TPU film according to claim 1, characterized in that, The light-shielding filler is a compound of rutile titanium dioxide and barium sulfate with a weight ratio of (1:1) to (1:3) and an average particle size of 0.2-0.8 μm.

3. The semi-opaque dual-color TPU film according to claim 1, characterized in that, The masterbatch is a high-concentration coloring masterbatch based on a polyurethane carrier, with a pigment content of ≥40%, and the color of the masterbatch is selected from black, gray, blue or red.

4. The semi-opaque dual-color TPU film according to claim 1, characterized in that, The interface compatibilizer is maleic anhydride-grafted thermoplastic polyurethane or an oxazoline-based compatibilizer.

5. The semi-opaque dual-color TPU film according to claim 1, characterized in that, The functional additives include at least one of UV stabilizers, antioxidants, and hydrolysis inhibitors.

6. The semi-opaque dual-color TPU film according to claim 1, characterized in that, The visible light transmittance of the light-transmitting area is 40%-70%, and the haze is ≤15%; the visible light shading rate of the light-shielding color-developing area is ≥90%, and the interfacial peel strength between the light-transmitting area and the light-transmitting area is ≥20 N / cm.

7. The semi-opaque dual-color TPU film according to claim 1, characterized in that, The film has a thickness of 0.05-0.5 mm, and the light-transmitting area and the light-blocking color-developing area are formed into an integrated structure through co-extrusion molding.

8. A method for preparing a semi-opaque dual-color TPU film as described in any one of claims 1-7, characterized in that, Includes the following steps: a) Prepare materials for the light-transmitting area and the light-blocking color-developing area separately: premix the respective formulation components and melt granulate; b) The two types of granules are added separately to the two independent extruders of the dual-channel co-extrusion system; c) Control the temperature of the two extruders at 170-200℃, and extrude and cast films synchronously through a co-extrusion die with partitioned flow channels; d) Cool, stretch, and wind up the formed film.

9. The preparation method according to claim 8, characterized in that, In step c), the partitioned flow channel in the co-extrusion die head is provided with a "dovetail" type interlocking structure to enhance the mechanical interlocking and fusion of materials in the two zones at the interface.

10. The application of a semi-opaque dual-color TPU film as described in any one of claims 1-7 in automotive interior sunshade mats, sports protective gear window components, smart watch straps, or high-end cosmetic packaging.