Secondary forming method of TPU carbon fiber soft cloth

Abstract

A secondary forming method of TPU carbon fiber soft cloth comprises the following steps of material preparation, laminated structure design, forming, mold taking and cutting, secondary forming and post-treatment, fusion of TPU and woven cloth is completed through primary hot pressing in the mode of two times of hot pressing forming and cold pressing forming, and shaping is completed through secondary hot pressing. Through innovative material combination and a stepped hot pressing-cold pressing process, molecular-level combination of the fiber cloth and TPU is achieved, the production process is optimized, the tensile strength, toughness and impact resistance are remarkably improved, the defects of an existing shoe material in the aspects of mechanical property, production efficiency and surface treatment can be overcome, and the shoe material is suitable for large-scale popularization and application. A high-strength, high-toughness, high-glossiness product is provided.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material manufacturing, and in particular relates to a secondary molding method of TPU carbon fiber soft cloth. Background Art

[0002] In the field of shoe material manufacturing, especially in the production of sports shoe side panels and heel support structures, reinforcing materials such as carbon fiber and glass fiber are widely used to improve the lightweight, strength and impact resistance of products. However, the existing technology has many shortcomings in achieving these goals. Traditional processes usually use pure carbon fiber or glass fiber hot pressing molding methods to make finished products through resin impregnation and high temperature and high pressure curing, but such products are often hard and lack toughness, which makes it difficult to meet the requirements of shoe materials for flexibility and comfort. Another common method is to use thermoplastic polyurethane (TPU) or other thermoplastic materials alone for molding. Although these materials have good flexibility, they are insufficient in terms of support and tensile strength, and cannot meet the needs of high-strength sports shoes. In addition, some manufacturers have tried to simply laminate TPU with fiber cloth to combine the advantages of the two, but due to problems such as insufficient material bonding and unreasonable hot pressing parameters, the finished products are easy to delaminate, have poor toughness or insufficient surface finish, affecting the overall performance and appearance quality of the product.

[0003] The main defects of the existing technology are reflected in many aspects. First, the material bonding force is poor. In the traditional lamination process, TPU and fiber cloth are only physically bonded, and molecular-level impregnation is not achieved, resulting in low interface bonding strength. The product is prone to cracking or delamination after repeated bending. Secondly, the production process is inefficient. Most processes require multiple independent steps such as pre-impregnation, molding and finishing, which not only prolongs the production cycle but also increases costs. Thirdly, there are obvious defects in the surface treatment of the finished product. The surface of the shoe material produced by the traditional process is rough or uneven in gloss, and additional spraying or lamination treatment is required, which not only increases environmental risks such as volatile organic compound (VOC) emissions, but also further increases production costs. In addition, the existing scheme is relatively simple in structural design, and it is difficult to take into account both high toughness and high support. For example, the carbon fiber is too hard and the TPU is too soft, which cannot adapt to the complex needs of sports shoes under dynamic mechanical conditions.

[0004] Previously, the key technical difficulties that the industry has failed to resolve have also restricted the development and promotion of similar technical solutions. For example, in terms of coordinated control of temperature and pressure, traditional processes can easily lead to excessive flow of TPU or embrittlement of fiber cloth due to improper parameter matching. The present invention achieves sufficient melt penetration and shaping of the material through differentiated temperature control and a stepped hot pressing-cold pressing process, while avoiding thermal damage and deformation problems. In terms of multi-layer material interface optimization, the existing technology is difficult to balance the differences in expansion coefficients between TPU, hot melt adhesive, fiber cloth and pearlescent paper, while the present invention significantly improves the interface bonding strength through sandwich structure design and secondary molding method. In addition, functional integration is also an important obstacle. The composite process of pearlescent paper and TPU has been mostly used for decorative materials before, and the present invention innovatively applies it to the field of footwear materials, while solving the needs of aesthetics and functionality, and overcoming the contradiction between fit fastness and surface finish.

[0005] Certain technical prejudices have long existed within the industry, such as the belief that "high toughness" and "high rigidity" are mutually exclusive and that pearlescent paper is only suitable for decorative layers. This invention, through the combination of TPU and fiber cloth and a secondary hot pressing process, successfully demonstrates that high toughness and high rigidity can be synergistically optimized. Through these innovations, this invention fills a technological gap in flexible, high-strength shoe material composites, significantly improves production efficiency and product performance, and provides a brand-new solution for the industry. Summary of the Invention

[0006] The present invention addresses the problem that existing shoe material composite materials have significant defects in mechanical properties, production efficiency and surface treatment. To this end, a secondary molding method of TPU carbon fiber soft cloth is provided. Through innovative material combination design and stepped hot pressing process, molecular-level bonding of fiber cloth and TPU is achieved, while the production process is optimized, significantly improving the tensile strength, toughness and impact resistance of the product.

[0007] A secondary molding method for TPU carbon fiber soft cloth, comprising the following steps: material preparation, laminate structure design, molding, mold taking and cutting, secondary molding and post-processing;

[0008] The material preparation includes preparing woven cloth, pearlescent paper and TPU film, and cutting them according to requirements;

[0009] The laminated structure design adopts a multi-layer material stacking method to stack woven fabric, pearlescent paper and TPU film;

[0010] The molding stage includes a hot pressing molding and a cold pressing molding. The superimposed materials are placed in the mold for the first time. During the hot pressing molding, the upper plate temperature of the mold is set to 125-135°C, the lower plate temperature is set to 165-175°C, the hot pressing time is 300-350 seconds, and the pressure is 100-150kg to fuse the TPU with the woven fabric. After the hot pressing is completed, cold pressing is performed. The cold pressing method is water cooling, the water temperature is 5-15°C, the cold pressing pressure is set to 100-120kg, and the cold pressing time is 180-200s.

[0011] The mold taking and cutting stage includes the product removal operation after the cold pressing is completed and the cutting operation based on the 2D unfolded plane diagram of the 3D product to obtain the TPU soft cloth with a planar structure;

[0012] In the secondary molding stage, the TPU soft cloth is placed in the mold again and subjected to a secondary hot pressing molding process. The secondary hot pressing process transforms the flat structure of the TPU soft cloth into the desired 3D shape structure. After the secondary hot pressing is completed, the finished product is taken out;

[0013] The post-processing stage includes trimming, metal detection, weighing and shipping operations.

[0014] As a further improvement, the fiber woven cloth is selected from one or more combinations of carbon fiber, glass fiber, aramid, and basalt fiber.

[0015] As a further improvement, the thickness of the TPU film is 0.3 mm to 0.5 mm, and a matte TPU film or a glossy TPU film is selected. The TPU film is a film without adhesive film, or a film with hot melt adhesive on one side.

[0016] As a further improvement, in the laminated structure design, at least one TPU film is laminated on both sides of the woven cloth, and pearlescent paper is laminated on the surface of at least one TPU film; or the TPU film is bonded to the woven cloth by hot melt adhesive.

[0017] As a further improvement, the stacked materials are laminated by pressing two upper and lower steel plates, and then subjected to a hot pressing process and a vacuum process to adsorb the materials and position the materials.

[0018] As a further improvement, during the secondary hot pressing molding, after the TPU soft cloth is put into the mold again, a TPU film or hot melt adhesive, or pearlescent paper, or PET film is attached to the TPU soft cloth.

[0019] As a further improvement, a laser cutting machine is used to cut the materials and finished products.

[0020] As a further improvement, during the secondary molding process, the surface roughness Ra of the finished product is adjusted from Ra≤0.1μm to Ra≥1.5μm by adding a PET film or TPU film.

[0021] The key technical innovations of this invention lie in the integrated application of material combination and laminate structure design, a stepped hot-cold pressing process, a secondary molding method, precision cutting and layout technology, and quality control processes. The material combination and laminate structure design achieve a combination of high strength and high toughness through a composite design of fiber woven cloth and thermoplastic materials. The integration of the functional layer eliminates the need for subsequent spraying or laminating processes. Furthermore, the stepped hot-cold pressing process, through differentiated temperature control technology and parameter optimization, ensures that the TPU melt penetrates the fiber cloth while protecting the pearlescent paper from high-temperature damage. Cold pressing allows for rapid shaping to prevent material deformation.

[0022] The overmolding method achieves the cup- or bowl-shaped structure required for the shoe side panels by converting a flat product into a 3D shape, while also enhancing product performance through the addition of a TPU layer. Precision cutting and layout technology utilizes a laser cutter to cut according to the unfolded drawing, ensuring a cutting accuracy error of no more than 0.2mm. Quality control utilizes a combination of metal detection and weighing to ensure product consistency, with a metal detection sensitivity of no less than 0.3mm and a weighing deviation of no more than ±0.5g.

[0023] The present invention is specifically characterized by a combination of high strength and high toughness, high surface gloss without the need for post-processing, significantly improved production efficiency, lightweight products, improved yield rate, and enhanced environmental protection. The combination of high strength and high toughness is achieved through the initial hot pressing process and secondary molding reinforcement of the TPU melt-impregnated fiber cloth, with the tensile strength increased by no less than 30%. High surface gloss is achieved without the need for post-processing through integrated hot pressing and synchronous molding of pearlescent paper or PE film, with the gloss reaching above 90GU. Significant improvement in production efficiency is achieved through an integrated hot pressing-cold pressing process and precise laser cutting, with the total time shortened to less than 510 seconds. Product lightweighting is achieved through the optimized compounding of fiber woven cloth and TPU, with a 20% reduction in density. Improved yield rate is achieved through the combination of metal detection and weighing, with a foreign matter detection rate of 100% and a mass deviation of no more than ±0.5g. Enhanced environmental protection is achieved by achieving zero VOC emissions by eliminating the spraying process.

[0024] The fiber woven cloth material can be replaced with glass fiber, aramid, basalt fiber, flax fiber or polyester fiber, and lightweight and reinforcement effects can still be achieved. Thermoplastic materials can be replaced with thermoplastic polyurethane elastomer (TPEE), polyethylene (PE) film or polypropylene (PP) film, among which TPEE provides higher resilience, and PE or PP film reduces cost but slightly reduces tensile strength. The surface layer of pearlescent paper can be replaced with PET mirror film, PU coated paper or electroplated aluminum film, all of which can achieve a high gloss effect, among which electroplated aluminum film has better wear resistance but the cost increases by 20%. The cold pressing method can be replaced with air cooling or metal plate conduction cooling, among which air cooling is more energy-efficient, and the metal plate cools faster but needs to prevent condensation. The secondary molding reinforcement layer can be replaced with an additional hot melt adhesive film, among which the hot melt adhesive film is thinner and easier to operate.

[0025] This invention solves the key defects of existing shoe material composite materials through innovative material combination design and stepped hot pressing process, while providing a wide range of technical coverage to ensure efficient, high-quality and environmentally friendly production processes in various application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall process flow of the present invention. DETAILED DESCRIPTION

[0027] In order to further understand the features, technical means, specific objectives and functions achieved by the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Combined with attachment Figure 1 As shown, a secondary molding method of TPU carbon fiber soft cloth includes cutting, lamination, mold application, mold removal, cutting, secondary molding, secondary mold removal, trimming, metal detection, weighing and shipping.

[0029] S1, in the material preparation stage, prepare woven cloth, TPU film, and pearlescent paper, and first perform cutting processing. Taking carbon fiber as an example, choose a plain or twill weave to form a woven cloth, and cut it into the required size according to the shape of the mold. At the same time, cut the TPU film and pearlescent paper into the same size as the woven cloth. Commonly used TPU films with a thickness of 0.3mm are matte or glossy, and 0.5mm TPU films can be used. It is also necessary to prepare hot melt adhesive, TPU film containing single-sided hot melt adhesive. Choose matte or glossy TPU film according to needs. The purpose of using pearlescent paper is to improve the glossiness of the product surface.

[0030] S2, laminate structure design, can have different stacking methods according to needs. For example, set up two TPU films, and sandwich a woven fabric between the two TPU films. Overall, there are many different stacking methods, such as: TPU film + woven fabric + TPU film + pearlescent paper, no need to remove the release paper on both sides; TPU film + hot melt adhesive + woven fabric + TPU film + pearlescent paper, no need to remove the release paper on both sides; pearlescent paper + TPU film + hot melt adhesive + woven fabric + TPU film + pearlescent paper, no need to remove the release paper on both sides. Different laminate structures can be flexibly selected according to production needs.

[0031] In step S3, the laminated materials are placed in a mold and covered with steel plates, with the upper and lower plates sandwiching the materials. The materials are then placed in a hot press for hot pressing. Differentiated temperature control is used during the hot pressing process: the upper plate temperature is set at 130°C, the lower plate temperature is set at 170°C, the hot pressing time is set at 330 seconds, and the pressure is set at 100 kg. During the hot pressing process, the TPU film melts and penetrates the interfiber gaps of the carbon fiber woven fabric, forming a molecular bond. Meanwhile, the pearlescent paper is protected from heat damage by the lower temperature of the upper plate, thus preserving its surface gloss. After hot pressing, the process immediately switches to cold pressing, with the water temperature set at 10°C, the cold pressing pressure also at 100 kg, and the cold pressing time for 180 seconds. This cold pressing process quickly sets the material, prevents TPU rebound deformation, and ensures product dimensional stability. The purpose of this initial hot pressing process is to melt the TPU film into the carbon fiber woven fabric, fully impregnating it and improving the product's toughness and tensile strength.

[0032] S4: After the cold pressing is completed, the product is removed from the mold and the pearlescent paper and release paper of the TPU film are removed to obtain the TPU soft cloth. The product obtained at this time is still in a flat state and needs to be further cut by a laser cutting machine. Laser cutting is based on the 2D unfolded plan view of the 3D product to ensure that the cutting accuracy error does not exceed 0.2mm. For example, the cup-shaped structure of the shoe side panel needs to be accurately laid out on the TPU soft cloth according to its unfolded shape and cut using a laser cutting machine. This step can effectively avoid material shortages or dimensional deviations, laying the foundation for subsequent secondary molding.

[0033] S5, the cut TPU soft cloth enters the secondary hot pressing molding stage, and the flat TPU soft cloth is placed in the mold again for hot pressing and shaping. The temperature of the secondary hot pressing is set to 120°C, the pressure is set to 60kg, and the time is 30 seconds. During the secondary molding process, TPU film can be added as needed to improve the strength of the product, or PE film can be added to adjust the surface roughness (Ra≤0.1μm to Ra≥1.5μm) to meet matte / glossy requirements. For example, for application scenarios that require higher tensile force, a layer of TPU film with the same size as the product can be applied when the flat product is put into the mold; for scenarios that focus on surface smoothness, a layer of PE film can be applied to make the product surface achieve a mirror effect. After the secondary molding is completed, the product is transformed from a flat surface into the required 3D shape structure, such as a cup or bowl shape, to meet the dynamic mechanical requirements of the shoe side panel or heel.

[0034] S6. After the secondary hot pressing is complete, the product is removed from the mold and trimmed. Use scissors to trim the rough edges of the product to ensure a neat appearance. The trimmed products are then placed one by one and placed in a metal detector for foreign object detection. The metal detector has a sensitivity of at least 0.3mm and can effectively eliminate harmful foreign objects such as knife tips and needle points. After passing the inspection, the products are weighed one by one on a weighing machine to ensure that the quality consistency deviation does not exceed ±0.5g. This step can significantly improve the product yield rate and meet high-quality production requirements.

[0035] Finally, in step S6, qualified products are stacked one by one, with a plastic protective film placed between the layers to prevent surface scratches. Once these steps are complete, shipment can begin. This entire process, through innovative material combination design and a stepped hot-pressing and cold-pressing process, addresses key flaws in existing shoe composite materials, achieving multiple advantages: a combination of high strength and toughness, a high surface gloss without the need for post-processing, significantly improved production efficiency, lightweight products, increased yield rates, and enhanced environmental friendliness.

[0036] This process also provides a variety of replacement options to adapt to different application scenarios. For example, the material of the fiber woven cloth 1 can be replaced with glass fiber, aramid, basalt fiber, flax fiber or polyester fiber, all of which can achieve lightweight and reinforcement effects. The TPU film can be replaced with thermoplastic polyurethane TPEE, polyethylene PE film or polypropylene PP film, among which TPEE provides higher resilience, and PE or PP film reduces cost but slightly reduces tensile strength. The surface layer of pearlescent paper can be replaced with PET mirror film, PU coated paper or electroplated aluminum film, all of which can achieve high gloss effect, among which electroplated aluminum film has better wear resistance but increases cost by 20%. The cold pressing method can be replaced with air cooling or metal plate conduction cooling, among which air cooling is more energy-efficient, and the metal plate cools faster but needs to prevent condensation. The secondary molding reinforcement layer can be replaced with an additional hot melt adhesive film, among which the hot melt adhesive film is thinner and easier to operate.

[0037] In practical applications, this process is suitable for the manufacture of high-performance sports shoe side panels, heel support structures, and decorative parts for fashion shoes. For medical protective gear or military protection, the stacking combination and process parameters can be adjusted to flexibly adapt to different mechanical performance requirements. For example, when making the side panels of professional sports shoes, a combination of carbon fiber woven cloth and TPU film is used, and a TPU layer is added during secondary molding, which can significantly improve the product's impact resistance and bending life. When making decorative parts for fashion shoes, the pearlescent paper integration process is used to achieve a mirror or matte effect, replacing the traditional spraying process and reducing environmental pollution.

[0038] In general, the secondary hot pressing and cold pressing treatment has the following advantages:

[0039] 1. Combination of high strength and high toughness - TPU film is melt-impregnated into fiber cloth during hot pressing process.

[0040] Secondary hot pressing and strengthening, by adding TPU layer or hot melt adhesive,

[0041] High surface gloss, no post-treatment required - Pearlescent paper / PE film integrated hot pressing, simultaneous molding.

[0042] Upper steel plate with low temperature protection pearl paper structure.

[0043] Production efficiency is significantly improved - the hot pressing and cold pressing integrated process eliminates the need for separate processes such as pre-preg and spraying.

[0044] Use laser cutting machine for precise laser cutting, with an error of ≤0.2mm.

[0045] Lightweight product - Optimized compounding of fiber woven cloth and TPU reduces density by 20%.

[0046] Improved yield rate - Metal detection + weighing combined, foreign matter detection rate 100%, quality deviation ≤

[0047] ±0.5g.

[0048] Enhanced environmental protection - the spraying process is eliminated, and zero VOC emissions can be achieved.

[0049] 2. The introduction of hot melt adhesive layer - the interface bonding strength is increased by 50%, completely solving the problem of easy delamination.

[0050] Add PE film during secondary molding - surface roughness is adjustable (Ra≤0.1μm to Ra≥1.5μm) to meet matte / glossy requirements

[0051] Dynamic parameter adjustment (temperature / pressure / time - adapt to products of different thicknesses / sizes (e.g., hot pressing time for large molds extended to 400s)

[0052] Multi-fiber blended design (such as carbon fiber + glass fiber) - 30% cost reduction and balanced mechanical properties (tensile strength ≥ 150MPa).

[0053] Cold pressing water temperature control (5-15℃) - avoids TPU rebound deformation and improves dimensional stability (warpage ≤ 0.1mm / m)

[0054] 3. Comparison of typical effect data

[0055] Mechanical properties:

[0056] Tensile strength: conventional process 120 MPa → present invention ≥ 160 MPa (+33%).

[0057] Bending life: traditional 50,000 times → this invention >100,000 times

[0058] Production efficiency:

[0059] The total time consumed by the traditional process is 600s → the present invention is ≤510s (shortened by 15%).

[0060] Surface quality:

[0061] The glossiness of traditional spray coating is 80GU → after hot pressing, the glossiness of pearlescent paper is ≥90GU.

[0062] 4. Benefits of extending the industrial chain

[0063] Shoe material field: Solve the contradiction between "lightweight and tear resistance" in the side panels of sports shoes and extend product life.

[0064] Cost control: Pearlescent paper replaces the spraying process, reducing the cost of each piece by ￥0.5.

[0065] It should be noted that the above description is not a limitation of the present invention. Without departing from the inventive concept of the present invention, any obvious replacement is within the scope of protection of the present invention.

Claims

1. A secondary molding method for TPU carbon fiber soft cloth, characterized in that: The process includes the following steps: material preparation, laminate structure design, molding, mold taking and cutting, secondary molding and post-processing; The material preparation includes preparing woven cloth, pearlescent paper and TPU film, and cutting them according to requirements; The laminated structure design adopts a multi-layer material stacking method to stack woven fabric, pearlescent paper and TPU film; The molding stage includes a hot pressing molding and a cold pressing molding. The superimposed materials are placed in the mold for the first time. During the hot pressing molding, the upper plate temperature of the mold is set to 125-135°C, the lower plate temperature is set to 165-175°C, the hot pressing time is 300-350 seconds, and the pressure is 100-150kg to fuse the TPU with the woven fabric. After the hot pressing is completed, cold pressing is performed. The cold pressing method is water cooling, the water temperature is 5-15°C, the cold pressing pressure is set to 100-120kg, and the cold pressing time is 180-200s. The mold taking and cutting stage includes the product removal operation after the cold pressing is completed and the cutting operation based on the 2D unfolded plane diagram of the 3D product to obtain the TPU soft cloth with a planar structure; In the secondary molding stage, the TPU soft cloth is placed in the mold again and subjected to a secondary hot pressing molding process. The secondary hot pressing process transforms the flat structure of the TPU soft cloth into the desired 3D shape structure. After the secondary hot pressing is completed, the finished product is taken out; The post-processing stage includes trimming, metal detection, weighing and shipping operations.

2. The secondary molding method of TPU carbon fiber soft cloth according to claim 1, characterized in that: The fiber woven cloth is selected from one or more combinations of carbon fiber, glass fiber, aramid, and basalt fiber.

3. The secondary molding method of TPU carbon fiber soft cloth according to claim 1, characterized in that: The thickness of the TPU film is 0.3 mm to 0.5 mm, and a matte TPU film or a glossy TPU film is selected. The TPU film is a film without adhesive film, or a film with hot melt adhesive on one side.

4. The secondary molding method of TPU carbon fiber soft cloth according to claim 1, characterized in that In the laminated structure design, at least one TPU film is adhered to both sides of the woven cloth, and pearlescent paper is adhered to the surface of at least one TPU film; or the TPU film is bonded to the woven cloth by hot melt adhesive.

5. The secondary molding method of TPU carbon fiber soft cloth according to claim 1, characterized in that The stacked materials are laminated by using upper and lower steel plates, and then subjected to a hot pressing process and a vacuum process to absorb the materials and position them.

6. The secondary molding method of TPU carbon fiber soft cloth according to claim 1, characterized in that: When performing secondary hot pressing molding, after the TPU soft cloth is placed in the mold again, TPU film or hot melt adhesive, or pearlescent paper, or PET film is attached to the TPU soft cloth.

7. The secondary molding method of TPU carbon fiber soft cloth according to claim 1, characterized in that: Laser cutting machines are used to cut various materials and finished products.

8. The secondary molding method of TPU carbon fiber soft cloth according to claim 7, characterized in that: During the secondary molding process, the surface roughness Ra of the finished product is adjusted from Ra≤0.1μm to Ra≥1.5μm by adding PET film or TPU film.

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