Cold-resistant thermoplastic polyurethane cable material and method for preparing the same

Abstract

The present application relates to the technical field of thermoplastic polyurethane cable material preparation, and discloses a cold-resistant thermoplastic polyurethane cable material and a preparation method thereof.The method adopts a staged gradient mixing and interface directional reinforcement process, sequentially passes through an inert atmosphere protection to prepare a pre-activated matrix composite composed of polycaprolactone TPU, a nano inorganic nucleating agent and a silane coupling agent, realizes molecular dispersion of a cold-resistant plasticizer, a high molecular weight polyester toughening agent and a hydrolysis-resistant stabilizer under the action of an ultrasonic field to form a low-temperature functional phase, and then carries out forced reactive blending and dynamic vulcanization of the two-phase material and a reactive compatibilizer and an antioxidant system in a multi-stage shearing zone and a static mixing zone in a double-screw extruder to obtain the final material by underwater hot cutting and granulation.The cable material prepared by the method has excellent low-temperature toughness and high-temperature stability, and is suitable for cable application requirements in various harsh temperature environments.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic polyurethane cable material preparation technology, specifically to a cold-resistant thermoplastic polyurethane cable material and its preparation method. Background Technology

[0002] Thermoplastic polyurethane (TPU) has been widely used in the cable material field due to its excellent mechanical properties, abrasion resistance, oil resistance, and good processability. It is particularly prevalent in industrial cables, automotive cables, and cables for special environments where high overall material performance is required. As cable applications expand, the temperature fluctuation range of their operating environments is gradually increasing, and extreme low and high temperature environments place more stringent demands on the performance of TPU cable materials. In cold regions or low-temperature conditions, conventional TPU cable materials are prone to decreased toughness and increased brittleness, leading to cracking and breakage during laying and use, affecting transmission performance and service life. In high-temperature environments, the material may soften, deform, and experience strength reduction, compromising the structural stability and safety of the cable.

[0003] To improve the cold resistance of TPU cable materials, existing technologies often employ modification methods such as adding plasticizers, introducing flexible segments, or blending elastomers. However, traditional plasticizer addition methods are prone to plasticizer migration and precipitation, which not only leads to a long-term decline in the material's cold resistance but may also affect its mechanical strength and aging resistance. Chemical modification methods that introduce flexible segments suffer from harsh reaction conditions, complex processes, and high costs, hindering industrial-scale promotion. While blending elastomers can improve low-temperature toughness to some extent, the poor compatibility between the elastomer and the TPU matrix can easily lead to phase separation, resulting in decreased high-temperature stability and failing to achieve a synergistic improvement in both low-temperature toughness and high-temperature stability.

[0004] To improve the high-temperature stability of materials, existing technologies often involve using hard segment components with high glass transition temperatures or adding inorganic fillers. However, hard segment components with high glass transition temperatures can further exacerbate the brittleness of materials at low temperatures, leading to a deterioration in low-temperature performance. The addition of inorganic fillers requires addressing the issue of uniform dispersion of the filler in the matrix. Poor dispersion not only fails to effectively improve high-temperature stability but also leads to a decrease in the mechanical properties of the material, stress concentration, and affects the reliability of cable materials. Summary of the Invention

[0005] The purpose of this invention is to provide a cold-resistant thermoplastic polyurethane cable material and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a cold-resistant thermoplastic polyurethane cable material and a method for preparing the same, the method comprising:

[0007] Achieving synergy between low-temperature toughness and high-temperature stability through a phased gradient mixing and interface-oriented reinforcement process includes: First, under an inert atmosphere, a pre-activated matrix composite consisting of polycaprolactone-type TPU, nano-inorganic nucleating agents, and silane coupling agents is prepared; Second, under an ultrasonic field, cold-resistant plasticizers, high-molecular-weight polyester toughening agents, and hydrolysis-resistant stabilizers are molecularly dispersed to form a low-temperature functional phase; Third, the above two-phase materials, along with a reactive compatibilizer and antioxidant system, are subjected to forced reactive blending and dynamic vulcanization in a twin-screw extruder through multi-stage shear zones and static mixing zones, followed by underwater hot-cut granulation to obtain the final material.

[0008] Preferably, the preparation of the first-stage pre-activated matrix composite specifically includes the following steps: First, vacuum-dried polycaprolactone-type TPU particles with a water content of less than 200 ppm are added to a high-speed mixer along with 0.5%-1.5% by mass of nano-montmorillonite and 0.2%-0.8% by mass of γ-aminopropyltriethoxysilane. The mixture is then mixed for 15-25 minutes at 600-800 r / min under a nitrogen atmosphere and at 60-80°C, allowing the silane coupling agent to graft onto the surface of the nanoparticles. Subsequently, the mixture is transferred to the feeding section of a first-stage twin-screw extruder, melted at 155-165°C in the mild shear zone of the screw, and dispersed in the subsequent low shear mixing zone for 5-10 minutes to form a uniform pre-activated matrix melt. After water cooling and pelletizing, the matrix composite masterbatch is obtained.

[0009] Preferably, the formation of the second-stage low-temperature functional phase specifically includes the following steps: adding propylene glycol adipate polyester, trioctyl trimellitate, and carbodiimide anti-hydrolysis agent in a mass ratio of (5-15):(8-12):(0.3-0.8) into a closed mixing vessel equipped with an ultrasonic probe; heating the mixing system to 80-100℃, turning on an ultrasonic field with a frequency of 20-40kHz, and treating it for 30-50 minutes under the synergistic effect of mechanical stirring and ultrasonic cavitation until the system presents a uniform, transparent, viscous liquid state, thereby obtaining a low-temperature functional phase concentrate.

[0010] Preferably, the third stage of forced reactive blending and dynamic vulcanization specifically includes the following steps: First, the matrix composite masterbatch obtained in the first stage, the low-temperature functional phase concentrate obtained in the second stage, 1%-3% by mass of epoxy-functionalized styrene-ethylene-butene-styrene block copolymer, and an antioxidant system composed of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1-2 are premixed at a mass ratio of 100:(8-18):(2-5):(0.5-1.5); Second, the premix is ​​fed from the main feed port into a co-rotating twin-screw extruder with special threaded elements, the screw configuration being sequentially set with solid conveying... The system consists of a melting and plasticizing section, two high-intensity shear dispersion sections, a static mixing and reaction section, and an exhaust homogenization section. A lateral liquid injection port is located after the melting and plasticizing section to precisely meter and inject the low-temperature functional phase concentrate into the melt. At a melt temperature of 180-200℃, the material undergoes localized instantaneous high shear in the high-intensity shear section, causing the epoxy groups of the epoxy-functionalized styrene-ethylene-butene-styrene block copolymer to react in situ with the urethane groups of the TPU, achieving interfacial chemical bonding. The melt then enters a reaction section equipped with a Kenics-type static mixer, where dynamic vulcanization and full dispersion are completed under low shear. Finally, after vacuum devolatilization and melt pump pressurization, it is granulated by an underwater pelletizing system.

[0011] Preferably, the process parameters of the twin-screw extruder are: screw speed 250-350 r / min, torque controlled between 60%-80%; the screw elements of the two high-strength shear dispersion sections are composed of a combination of kneading blocks and anti-thread elements, and the shear rates are respectively set to 1200-1500 s. -1 and 800-1000 s -1 The length of the static mixing reaction section is 15-20 times the screw diameter, and the melt residence time is 40-60 seconds.

[0012] Preferably, an online melt viscosity and infrared spectroscopy monitoring device is installed after the exhaust homogenization section and before the die head of the twin-screw extruder to monitor the intrinsic viscosity and characteristic functional group peak area ratio of the melt in real time, and to finely adjust the shear section temperature and lateral liquid injection rate based on the feedback data, so that the melt flow rate of the final product is stabilized in the range of 5-15 g / 10min.

[0013] Preferably, the nano-montmorillonite in the first stage is an organically modified layered silicate with an interlayer spacing of 2.5-3.5 nm as determined by XRD. During the first-stage twin-screw extrusion process, by controlling the shear strength and residence time, it achieves intercalation or partial exfoliation in the TPU matrix.

[0014] Preferably, the number average molecular weight of the propylene glycol adipate polyester is 2000-4000 g / mol, and the pour point of the trioctyl trimellitate is below -50℃. Both need to be dehydrated at 100-120℃ and vacuum degree -0.095MPa for 2-4 hours before ultrasonic treatment.

[0015] Preferably, the present invention also includes a cold-resistant thermoplastic polyurethane cable material, which is prepared by the above-described method for preparing a cold-resistant thermoplastic polyurethane cable material.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] The first stage involves preparing a pre-activated matrix composite under an inert atmosphere. This prevents oxidative degradation of polycaprolactone-based TPU during processing. Simultaneously, the bridging effect of the silane coupling agent achieves a tight bond between the nano-inorganic nucleating agent and the TPU matrix, improving the matrix's crystallinity and structural stability. The uniform dispersion of the nano-inorganic nucleating agent refines the grains and reduces crystal defects, making the matrix material less prone to stress concentration at low temperatures. This lays the structural foundation for improved low-temperature toughness and also enhances the material's structural stability at high temperatures, preventing crystal melting and deformation due to high temperatures.

[0018] The second stage employs ultrasonic field manipulation to achieve molecular-level dispersion of the low-temperature functional phase. Compared to traditional mechanical mixing methods, the high-frequency vibrations generated by the ultrasonic field effectively break down the intermolecular forces between the cold-resistant plasticizer, high-molecular-weight polyester toughening agent, and hydrolysis-resistant stabilizer, promoting full contact and fusion of the components and achieving uniform dispersion at the molecular level. This uniform dispersion ensures that the low-temperature functional phase forms a continuous, flexible network structure within the material. When the material is in a low-temperature environment, this flexible network absorbs external energy, inhibits rigid molecular chain movement, prevents brittle fracture, and significantly improves the material's low-temperature toughness. Simultaneously, the molecular-level dispersion of the hydrolysis-resistant stabilizer ensures its uniform distribution within the material, effectively suppressing performance degradation caused by hydrolysis during use and extending the material's service life.

[0019] The third stage involves forced reactive blending and dynamic vulcanization via a multi-stage shearing zone and a static mixing zone in a twin-screw extruder. The multi-stage shearing zone generates strong shearing action, further refining the dispersed phase size of the pre-activated matrix composite and the low-temperature functional phase, promoting interfacial fusion between the two phases. The static mixing zone ensures stable mixing of the materials, preventing molecular chain breakage due to excessive shearing and maintaining the structural integrity of the material. During forced blending, the reactive compatibilizer reacts chemically with the molecular chains of the two phases, forming stable chemical bonds, strengthening the interfacial bonding between the two phases, effectively inhibiting phase separation, and improving the phase structure stability of the material. The dynamic vulcanization process enables the material to form a cross-linked network structure. This cross-linked network restricts the movement of molecular chains under high-temperature conditions, preventing softening and deformation. Simultaneously, the cross-linked structure enhances the material's mechanical strength and elastic recovery properties, allowing it to quickly return to its original shape under external forces and reducing permanent deformation. Attached Figure Description

[0020] Figure 1 This diagram illustrates the steps of preparing a cold-resistant thermoplastic polyurethane cable material according to the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments to enable those skilled in the art to understand it. It should be noted that the following embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention. Conventional adjustments to the process parameters of the present invention made under the premise of the present invention's concept are all within the scope of protection of the present invention.

[0022] The specific specifications of the raw materials used in this embodiment and comparative example are as follows. Unless otherwise specified, all raw materials are commercially available industrial-grade products:

[0023] Polycaprolactone-type TPU: grade PCL-TPU 3150, number average molecular weight 80000 g / mol, Shore A hardness 92, manufacturer is Yantai Wanhua Chemical Group Co., Ltd.;

[0024] Nano-montmorillonite: an organically modified product, with cetyltrimethylammonium bromide as the modifier, interlayer spacing of 3.2 nm (XRD determination), particle size of 50-100 nm, and manufactured by Zhejiang Fenghong New Material Co., Ltd.

[0025] Silane coupling agent: γ-aminopropyltriethoxysilane (KH-550), purity ≥98%, manufacturer is Nanjing Shuguang Chemical Group Co., Ltd.;

[0026] Propylene glycol adipate polyester: number average molecular weight 3000 g / mol, hydroxyl value ≤10 mg KOH / g, manufacturer is Jiangsu Haian Petrochemical Plant;

[0027] Trioctyl trimellitate: pour point -55℃, purity ≥99%, manufacturer is Zengcheng Kede Chemical Co., Ltd.;

[0028] Carbodiimide anti-hydrolysis agent: brand name Stabaxol P200, purity ≥98%, manufacturer is Rheinland Chemicals, Germany;

[0029] Reactive compatibilizer: epoxy-functionalized styrene-ethylene-butene-styrene block copolymer (SEBS), epoxy value 0.35 mmol / g, manufactured by Kraton Polymers, Inc., USA;

[0030] Antioxidant 1010: Hindered phenol, chemical name is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], purity ≥99%;

[0031] Antioxidant 168: Phosphite, chemical name tris(2,4-di-tert-butylphenyl) phosphite, purity ≥99%;

[0032] Ordinary montmorillonite: without organic modification, interlayer spacing 1.2 nm, manufactured by Zhejiang Fenghong New Material Co., Ltd.

[0033] Common plasticizer: Dioctyl phthalate (DOP), pour point -25℃, manufactured by Zengcheng Kede Chemical Co., Ltd.

[0034] The testing instruments and standards used in this embodiment and comparative example are as follows:

[0035] Low-temperature embrittlement temperature: Tested according to GB / T 5470-2008 "Determination of impact embrittlement temperature of plastics", with a sample size of 10 mm × 10 mm × 2 mm;

[0036] Tensile properties: Tested according to GB / T 1040.2-2006 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", with a tensile rate of 50 mm / min and a dumbbell-shaped 1A specimen.

[0037] Heat distortion temperature: Tested according to GB / T 1633-2000 "Determination of Vicat softening temperature (VST) and heat distortion temperature (HDT) of thermoplastics", with a load of 1.80 MPa and a heating rate of 120℃ / h.

[0038] Melt flow rate (MFR): Tested according to GB / T 3682.1-2018 "Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastic plastics - Part 1: Standard method", test temperature 210℃, load 2.16 kg;

[0039] Hydrolysis resistance: Tested according to GB / T 15905-1995 "Determination of the effects of exposure to damp heat, water spray and salt spray on plastics", with conditions of 70℃, relative humidity of 95%, test time of 1000 h, and tensile strength retention rate before and after the test;

[0040] XRD analysis: A Rigaku D / max-2500 X-ray diffractometer was used with a Cu target and Kα radiation. The scanning range was 2θ = 1-10° and the scanning rate was 2° / min.

[0041] Online melt viscosity and infrared spectroscopy combined monitoring device: adopts a combined system of HAAKE MARS60 rheometer and Nicolet iS50 infrared spectrometer from Thermo Fisher Scientific, Germany.

[0042] Example 1

[0043] See appendix Figure 1 This embodiment describes a method for preparing a cold-resistant thermoplastic polyurethane cable material, which employs a staged gradient mixing and interface directional reinforcement process. The specific steps are as follows:

[0044] 1. First stage: Preparation of pre-activated matrix complex

[0045] First, place polycaprolactone-type TPU particles in a vacuum drying oven and dry them at 120℃ and a vacuum of -0.095MPa for 4 hours until the moisture content is below 200ppm. Weigh 100kg of dried polycaprolactone-type TPU, 1.0kg of nano-montmorillonite (mass fraction 1.0%), and 0.5kg of γ-aminopropyltriethoxysilane (mass fraction 0.5%), and add them together to a high-speed mixer. Introduce nitrogen into the high-speed mixer to maintain an inert atmosphere, set the mixing temperature to 70℃ and the rotation speed to 700r / min, and mix for 20 minutes to allow the silane coupling agent to fully perform surface grafting modification on the nanoparticles.

[0046] Subsequently, the above mixture was transferred to the feeding section of the first-stage twin-screw extruder. The screw diameter of the first-stage twin-screw extruder was 35 mm, and the length-to-diameter ratio (L / D) was 36. The temperatures of each section of the screw were set as follows: feeding section 80℃, compression section 150℃, melting section 160℃, and die head 165℃. The screw speed was set to 150 r / min. The material melted at 160℃ in the mild shear zone (melting section) of the screw and then dispersed for 8 minutes in the subsequent low shear mixing zone to form a uniform pre-activated matrix melt. After the melt was cooled to room temperature by water cooling, it was pelletized by a pelletizer to obtain matrix composite masterbatch with a particle size of 2-3 mm.

[0047] XRD analysis showed that the interlayer spacing of nano-montmorillonite in the obtained matrix composite masterbatch was 3.0 nm, exhibiting a mixed state of intercalation-exfoliation.

[0048] 2. Second stage: Formation of low-temperature functional phases

[0049] Weigh 10 kg of propylene glycol adipate polyester, 10 kg of trioctyl trimellitate, and 0.5 kg of carbodiimide anti-hydrolysis agent, and add them to a closed mixing vessel equipped with an ultrasonic probe at a mass ratio of 10:10:0.5. First, place the propylene glycol adipate polyester and trioctyl trimellitate in a vacuum drying oven and dehydrate them for 3 hours at 110℃ and a vacuum degree of -0.095MPa. Then, add them to the mixing vessel and mix with the anti-hydrolysis agent.

[0050] Turn on the heating system of the mixing vessel and heat the mixing system to 90°C. Turn on the ultrasonic probe and set the ultrasonic frequency to 30kHz and ultrasonic power to 500W. At the same time, turn on the mechanical stirrer and set the stirring speed to 300r / min. Under the combined effect of mechanical stirring and ultrasonic cavitation, process for 40 minutes, taking samples every 10 minutes during the process, until the system presents a homogeneous, transparent, viscous liquid state. Stop the ultrasonication and stirring, and allow it to cool naturally to room temperature to obtain a low-temperature functional phase concentrate for later use.

[0051] 3. Third stage: Forced reactive blending and dynamic vulcanization

[0052] Step 1, Premixing: Weigh 100 kg of the matrix complex masterbatch obtained in the first stage, 13 kg of the low-temperature functional phase concentrate obtained in the second stage, 3 kg of SEBS (mass fraction 3.0%), and 1.0 kg of antioxidant system (antioxidant 1010 and antioxidant 168 are compounded at a mass ratio of 1:1.5, i.e., antioxidant 1010 0.4 kg and antioxidant 168 0.6 kg). Add the above materials to a low-speed mixer and mix at 100 r / min for 5 minutes at room temperature to obtain a uniform premix.

[0053] The second step is twin-screw extrusion, blending, vulcanization, and granulation: The premixed material is fed into a co-rotating twin-screw extruder with special screw elements through the main feed port. The screw diameter of this twin-screw extruder is 65 mm, and the length-to-diameter ratio is L / D=48. The screw configuration is as follows: solid conveying section (length is 8 times the screw diameter), melt plasticizing section (length is 10 times the screw diameter), first high-intensity shear dispersion section (length is 4 times the screw diameter), second high-intensity shear dispersion section (length is 3 times the screw diameter), static mixing reaction section (length is 18 times the screw diameter, with a built-in Kenics-type static mixer), and exhaust homogenization section (length is 5 times the screw diameter). A side liquid injection port is set at the end of the melt plasticizing section. The low-temperature functional phase concentrate is precisely metered and injected into the melt through a metering pump, and the injection rate is matched with the main feed rate.

[0054] The temperatures of each section of the twin-screw extruder are set as follows: solid conveying section 120℃, melt plasticizing section 170℃, first high-intensity shear dispersion section 190℃, second high-intensity shear dispersion section 195℃, static mixing reaction section 185℃, exhaust homogenization section 180℃, and die head 185℃; the screw speed is set to 300 r / min, and the torque is controlled at 70%; the shear rate of the first high-intensity shear dispersion section is set to 1400 s⁻¹, and the shear rate of the second high-intensity shear dispersion section is set to 900 s⁻¹; the residence time of the melt in the static mixing reaction section is 50 seconds.

[0055] After the exhaust homogenization section and before the die head, the online melt viscosity and infrared spectroscopy monitoring device is turned on to monitor the intrinsic viscosity of the melt and the peak area ratio of epoxy groups (characteristic peak 1250 cm⁻¹) and urethane groups (characteristic peak 1730 cm⁻¹) in real time. Based on the monitoring data, the temperature of the first and second high-intensity shear dispersion sections is finely adjusted (fine adjustment range ±5℃) and the lateral liquid injection rate is finely adjusted (fine adjustment range ±0.2 kg / h) to stabilize the melt flow rate of the final product in the range of 8-12 g / 10min.

[0056] After the melt is vacuum devolatilized (vacuum degree -0.09MPa) and pressurized by the melt pump (pressure stabilized at 15MPa), it is granulated by an underwater pelletizing system. The cooling water temperature is controlled at 25℃ and the pelletizing speed is 1500r / min, to obtain the final cold-resistant thermoplastic polyurethane cable material granules.

[0057] Example 2

[0058] This embodiment describes a method for preparing a cold-resistant thermoplastic polyurethane cable material. Except for the following parameter adjustments, the remaining steps are exactly the same as in Embodiment 1:

[0059] First stage: 0.5 kg of nano-montmorillonite (mass fraction 0.5%) and 0.2 kg of γ-aminopropyltriethoxysilane (mass fraction 0.2%) were added; the high-speed mixing temperature was 60℃ and the speed was 600 r / min, and the mixing time was 25 minutes; the melting zone temperature of the first-stage twin-screw extruder was 155℃, and the dispersion time in the low-shear mixing zone was 10 minutes.

[0060] Second stage: 5 kg of propylene glycol adipate polyester, 8 kg of trioctyl trimellitate, and 0.3 kg of carbodiimide anti-hydrolysis agent in a mass ratio of 5:8:0.3; the mixed system is heated to 80℃, ultrasonically treated at 20 kHz for 50 minutes; the dehydration conditions for propylene glycol adipate polyester and trioctyl trimellitate are 100℃ for 3 hours.

[0061] The third stage: the premix ratio is 100 kg of matrix composite masterbatch, 8 kg of low-temperature functional phase concentrate, 2 kg of SEBS, and 0.5 kg of antioxidant system (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1); the twin-screw extruder has a screw speed of 250 r / min and a torque of 60%; the shear rate of the first high-intensity shear dispersion section is 1200 s⁻¹, and the shear rate of the second high-intensity shear dispersion section is 800 s⁻¹; the length of the static mixing reaction section is 15 times the screw diameter, and the melt residence time is 60 seconds; online monitoring and control of the final product MFR stabilizes at 5-8 g / 10 min.

[0062] Example 3

[0063] This embodiment describes a method for preparing a cold-resistant thermoplastic polyurethane cable material. Except for the following parameter adjustments, the remaining steps are exactly the same as in Embodiment 1:

[0064] First stage: 1.5 kg of nano-montmorillonite (1.5% by mass) and 0.8 kg of γ-aminopropyltriethoxysilane (0.8% by mass) were added; the high-speed mixing temperature was 80℃ and the speed was 800 r / min, and the mixing time was 15 minutes; the melting zone temperature of the first-stage twin-screw extruder was 165℃, and the dispersion time in the low-shear mixing zone was 5 minutes.

[0065] Second stage: 15 kg of propylene glycol adipate polyester, 12 kg of trioctyl trimellitate, and 0.8 kg of carbodiimide anti-hydrolysis agent in a mass ratio of 15:12:0.8; the mixed system was heated to 100℃ and treated with ultrasonic frequency of 40 kHz for 30 minutes; the dehydration conditions for propylene glycol adipate polyester and trioctyl trimellitate were 120℃ for 2 hours.

[0066] The third stage: the premix ratio is 100 kg of matrix composite masterbatch, 18 kg of low-temperature functional phase concentrate, 5 kg of SEBS, and 1.5 kg of antioxidant system (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2); the twin-screw extruder has a screw speed of 350 r / min and a torque of 80%; the shear rate of the first high-intensity shear dispersion section is 1500 s⁻¹, and the shear rate of the second high-intensity shear dispersion section is 1000 s⁻¹; the length of the static mixing reaction section is 20 times the screw diameter, and the melt residence time is 40 seconds; online monitoring and control of the final product MFR stabilizes at 12-15 g / 10 min.

[0067] Comparative Example 1

[0068] This comparative example did not use a pre-activated matrix complex preparation process; instead, polycaprolactone-type TPU was directly mixed with other raw materials and extruded. The specific steps are as follows:

[0069] 1. Raw material pretreatment: Polycaprolactone-type TPU particles were dried at 120℃ and vacuum degree -0.095MPa for 4 hours until the moisture content was less than 200ppm; propylene glycol adipate polyester and trioctyl trimellitate were dehydrated at 110℃ and vacuum degree -0.095MPa for 3 hours.

[0070] 2. Premixing: Weigh 100kg of dried TPU, 1.0kg of nano-montmorillonite, 0.5kg of γ-aminopropyltriethoxysilane, 10kg of propylene glycol adipate polyester, 10kg of trioctyl trimellitate, 0.5kg of carbodiimide anti-hydrolysis agent, 3kg of SEBS, and 1.0kg of antioxidant system, add them to a high-speed mixer, mix at 70℃ and 700r / min for 20 minutes to obtain the premix.

[0071] 3. Extrusion granulation: The premixed material is added to a co-rotating twin-screw extruder (same model and screw configuration as in Example 1), and the temperature of each section is set to be the same as in Example 1; the screw speed is 300 r / min and the torque is 70%; no side liquid injection port is set, and no online melt viscosity and infrared spectrum monitoring is performed; the melt is vacuum devolatilized and pressurized by a melt pump before being granulated underwater to obtain cable material particles.

[0072] Comparative Example 2

[0073] In this comparative example, ultrasonic field-assisted dispersion was not used when preparing the low-temperature functional phase. The remaining steps were the same as in Example 1, with the following specific adjustments:

[0074] Second stage: 10 kg of propylene glycol adipate polyester, 10 kg of trioctyl trimellitate, and 0.5 kg of carbodiimide anti-hydrolysis agent were added to a closed mixing vessel, heated to 90°C, and treated with mechanical stirring (300 r / min) for 40 minutes to obtain a low-temperature functional phase (a milky white turbid liquid); the subsequent third stage steps were completely consistent with those in Example 1.

[0075] Comparative Example 3

[0076] This comparative example did not use the reactive compatibilizer SEBS, and the twin-screw extruder did not have a static mixing reaction section. The remaining steps were the same as in Example 1, with the following specific adjustments:

[0077] Third stage premixing: Weigh 100 kg of matrix complex masterbatch, 13 kg of low temperature functional phase concentrate, and 1.0 kg of antioxidant system, and mix them to obtain premix (SEBS-free).

[0078] The screw configuration of the twin-screw extruder was adjusted to include: a solid conveying section, a melt plasticizing section, a first high-intensity shear dispersion section, a second high-intensity shear dispersion section, and a venting homogenization section, while the static mixing reaction section was removed. The parameters such as temperature, screw speed, and shear rate of each section were consistent with those in Example 1. Online melt viscosity and infrared spectroscopy monitoring were not performed.

[0079] Table 1: Summary of Raw Material Formulations and Key Process Parameters for Examples and Comparative Examples

[0080]

[0081] Examples 1-3 follow the phased gradient mixing and interface-oriented reinforcement process of this invention, with reasonable adjustments only to the nano-montmorillonite, silane coupling agent, low-temperature functional phase ratio, and extrusion process parameters. They all include core technical features such as pre-activated matrix composite preparation, ultrasonic-assisted low-temperature functional phase dispersion, SEBS compatibilizer addition, and static mixing reaction section setting. Comparative Example 1 lacks the phased preparation process of the pre-activated matrix composite and directly mixes all raw materials; Comparative Example 2 lacks the ultrasonic field-assisted dispersion step; Comparative Example 3 lacks the SEBS reactive compatibilizer and static mixing reaction section. Through the above variable design, the necessity of each core process of this invention can be clearly verified.

[0082] Table 2: Test Results of Basic Performance of Cable Materials in Examples and Comparative Examples

[0083]

[0084] Table 2 Data Analysis:

[0085] Low-temperature performance: The low-temperature embrittlement temperatures of Examples 1-3 were all below -58℃, with Example 3 reaching the lowest at -65℃, significantly better than Comparative Examples 1-3 (-45~-50℃). This is because the examples used ultrasound-assisted preparation of the low-temperature functional phase, enabling molecular-level dispersion of propylene glycol adipate and trioctyl trimellitate, forming a uniform low-temperature toughening network; simultaneously, the intercalated-exfoliated nano-montmorillonite in the pre-activated matrix composite could inhibit the crystallization of TPU molecular chains at low temperatures, further improving cold resistance. Comparative Example 1, lacking pre-activation, experienced nano-montmorillonite agglomeration, failing to exert a toughening effect; Comparative Example 2, without ultrasound assistance, had uneven dispersion of the low-temperature functional phase, with localized agglomeration, resulting in limited improvement in cold resistance; Comparative Example 3 lacked SEBS compatibilizer, leading to weak interfacial bonding between the matrix and the low-temperature functional phase, making phase separation prone to occur at low temperatures, resulting in an increased embrittlement temperature.

[0086] Mechanical properties: The tensile strength of Examples 1-3 was 30.2~34.8 MPa, and the elongation at break was 550%~620%, both superior to Comparative Examples 1-3. In the examples, the epoxy groups of SEBS reacted in situ with the urethane groups of TPU, achieving interfacial chemical bonding and improving the interfacial bonding force; the low-shear dispersion of the static mixing reaction section made the components more uniformly mixed, further optimizing the mechanical properties. In Comparative Example 1, direct mixing led to the agglomeration of nano-montmorillonite, resulting in stress concentration and a decrease in tensile strength and elongation at break; in Comparative Example 2, the functional phase was unevenly dispersed at low temperature, with many interfacial defects and poor mechanical properties; Comparative Example 3 had no SEBS compatibilizer and no static mixing section, resulting in poor interfacial bonding force and the worst mechanical properties.

[0087] High-temperature stability: The heat distortion temperatures of Examples 1-3 were 85-92℃, higher than those of Comparative Examples 1-3 (72-80℃). This is because the intercalation structure formed by the pre-activated nano-montmorillonite hinders the thermal movement of TPU molecular chains, improving dimensional stability at high temperatures; the chemical bonding between SEBS and TPU forms a cross-linked network, further enhancing high-temperature rigidity. In Comparative Example 1, the nano-montmorillonite aggregated and could not form effective support; Comparative Example 3 lacked a cross-linked network, resulting in easy sliding of molecular chains at high temperatures and the lowest heat distortion temperature.

[0088] Processing fluidity: The MFR of Examples 1-3 was stable at 6.8~13.5 g / 10 min, which meets the processing requirements of cable materials; Comparative Example 1 had uneven dispersion due to direct mixing of raw materials, resulting in high melt viscosity and an MFR of only 4.5 g / 10 min, making processing difficult; Comparative Example 3 had no SEBS crosslinking effect, resulting in low melt viscosity and an MFR as high as 18.2 g / 10 min, which easily led to flow during processing; The Examples effectively ensured the stability of MFR and improved processing consistency by adjusting process parameters through online monitoring.

[0089] Table 3: Long-term aging performance test results of cable materials in the examples and comparative examples

[0090]

[0091] After aging at 70℃ and 95%RH for 1000 hours, Examples 1-3 exhibited tensile strength retention of 85%~90% and elongation at break retention of 82%~87%, significantly higher than Comparative Examples 1-3. This is because the present invention adds a carbodiimide-based anti-hydrolysis agent to the low-temperature functional phase and disperses it uniformly using ultrasound, effectively inhibiting the hydrolytic degradation of TPU; simultaneously, the physical barrier formed by the pre-activated nano-montmorillonite hinders the penetration of water molecules, further enhancing the anti-hydrolysis performance. In Comparative Example 1, the barrier effect failed due to the aggregation of nano-montmorillonite; in Comparative Example 2, the anti-hydrolysis agent was unevenly dispersed, with insufficient local concentration, resulting in poor anti-hydrolysis effect; in Comparative Example 3, the interfacial bonding was weak, allowing water molecules to easily penetrate at the interface, leading to accelerated hydrolysis.

[0092] Examples 1-3, after aging in hot air at 120℃ for 500 hours, exhibited a tensile strength retention rate of 80%~84% and an elongation at break retention rate of 75%~80%, which are superior to the comparative examples. The compound antioxidant system (1010+168) in these examples synergistically inhibits the thermo-oxidative degradation of TPU. 1010 acts as the primary antioxidant to capture free radicals, while 168 acts as an auxiliary antioxidant to decompose hydrogen peroxide. Simultaneously, the cross-linked network formed by SEBS and TPU reduces the thermal motion of molecular chains, lowering the oxidation rate. In contrast, Comparative Examples 1-3, due to uneven dispersion of components or interfacial defects, failed to fully utilize the antioxidants, resulting in a more significant performance decline after thermo-oxidative aging.

[0093] This invention utilizes a phased gradient mixing and interface-oriented reinforcement process to sequentially prepare a pre-activated matrix composite and an ultrasonically dispersed low-temperature functional phase. Following forced reactive blending and dynamic vulcanization, this effectively achieves a synergistic improvement in the low-temperature toughness and high-temperature stability of cold-resistant thermoplastic polyurethane cable materials. The cable materials prepared in Examples 1-3 exhibit a low-temperature embrittlement temperature below -58℃, a tensile strength above 30MPa, a heat distortion temperature above 85℃, and a performance retention rate above 80% after long-term aging, demonstrating excellent overall performance.

[0094] Comparative analysis shows that the pre-activated matrix composite preparation process can improve the dispersion effect of nano-montmorillonite, enhance the mechanical properties and high-temperature stability of the material; ultrasonic-assisted dispersion can ensure the uniformity of the low-temperature functional phase and significantly improve cold resistance; the combination of reactive compatibilizer SEBS and the static mixing reaction section can strengthen interfacial chemical bonding, optimize the compatibility of each component, and improve the overall performance of the material. The process design of this invention is reasonable, and the steps work synergistically. The prepared cable material can meet the requirements for cable coating in low-temperature, high-temperature, and harsh environments, and has broad application prospects.

[0095] 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.

Claims

1. A method for preparing a cold-resistant thermoplastic polyurethane cable material, characterized in that, The method includes: Achieving synergy between low-temperature toughness and high-temperature stability through a phased gradient mixing and interface-oriented reinforcement process includes: First, under an inert atmosphere, a pre-activated matrix composite consisting of polycaprolactone-type TPU, nano-inorganic nucleating agents, and silane coupling agents is prepared; Second, under an ultrasonic field, cold-resistant plasticizers, high-molecular-weight polyester toughening agents, and hydrolysis-resistant stabilizers are molecularly dispersed to form a low-temperature functional phase; Third, the above two-phase materials, along with a reactive compatibilizer and antioxidant system, are subjected to forced reactive blending and dynamic vulcanization in a twin-screw extruder through multi-stage shear zones and static mixing zones, followed by underwater hot-cut granulation to obtain the final material. The preparation of the first-stage pre-activated matrix composite specifically includes the following steps: First, vacuum-dried polycaprolactone-type TPU particles with a water content of less than 200 ppm are added to a high-speed mixer along with 0.5%-1.5% by mass of nano-montmorillonite and 0.2%-0.8% by mass of γ-aminopropyltriethoxysilane. The mixture is then mixed for 15-25 minutes at 600-800 r / min under a nitrogen atmosphere and at 60-80°C, allowing the silane coupling agent to graft onto the surface of the nanoparticles. Subsequently, the mixture is transferred to the feed section of a first-stage twin-screw extruder and melted at 155-165°C in the mild shear zone of the screw. It is then dispersed in the subsequent low-shear mixing zone for 5-10 minutes to form a uniform pre-activated matrix melt. After water cooling and pelletizing, the matrix composite masterbatch is obtained. The first-stage nano-montmorillonite was organically modified with hexadecyltrimethylammonium bromide, and its interlayer spacing was measured to be between 2.5-3.5 nm by XRD. In the first-stage twin-screw extrusion process, by controlling the shear strength and residence time, it was made to achieve intercalation or partial exfoliation in the TPU matrix. The formation of the second-stage low-temperature functional phase specifically includes the following steps: adding propylene glycol adipate polyester, trioctyl trimellitate, and carbodiimide anti-hydrolysis agent in a mass ratio of (5-15):(8-12):(0.3-0.8) into a closed mixing vessel equipped with an ultrasonic probe; heating the mixing system to 80-100℃, turning on an ultrasonic field with a frequency of 20-40kHz, and treating it for 30-50 minutes under the synergistic effect of mechanical stirring and ultrasonic cavitation until the system presents a homogeneous, transparent, viscous liquid state, thus obtaining a low-temperature functional phase concentrate; The third stage of forced reactive blending and dynamic vulcanization specifically includes the following steps: First, the matrix composite masterbatch obtained in the first stage, the low-temperature functional phase concentrate obtained in the second stage, 1%-3% by mass of epoxy-functionalized styrene-ethylene-butene-styrene block copolymer, and an antioxidant system composed of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1-2 are premixed at a mass ratio of 100:(8-18):(2-5):(0.5-1.5); Second, the premix is ​​fed from the main feed port into a co-rotating twin-screw extruder with special threaded elements. The screw configuration is sequentially set with a solid conveying section and a melt plastic section. The system consists of a melting and plasticizing section, two high-intensity shear dispersion sections, a static mixing reaction section, and an exhaust homogenization section. A lateral liquid injection port is located after the melting and plasticizing section to precisely meter and inject the low-temperature functional phase concentrate into the melt. At a melt temperature of 180-200℃, the material undergoes localized instantaneous high shear in the high-intensity shear dispersion section, causing the epoxy groups of the epoxy-functionalized styrene-ethylene-butene-styrene block copolymer to react in situ with the urethane groups of the TPU, achieving interfacial chemical bonding. The melt then enters the static mixing reaction section equipped with a Kenics-type static mixer, where dynamic vulcanization and full dispersion are completed under low shear. Finally, after vacuum devolatilization and melt pump pressurization, it is granulated by an underwater pelletizing system.

2. The method for preparing a cold-resistant thermoplastic polyurethane cable material according to claim 1, characterized in that, The process parameters of the twin-screw extruder are: screw speed 250-350 r / min, torque controlled between 60%-80%; the screw elements of the two high-strength shear dispersion sections are composed of a combination of kneading blocks and reverse thread elements, and the shear rate is set to 1200-1500 s. -1 and 800-1000 s -1 The length of the static mixing reaction section is 15-20 times the screw diameter, and the melt residence time is 40-60 seconds.

3. The method for preparing a cold-resistant thermoplastic polyurethane cable material according to claim 2, characterized in that, An online melt viscosity and infrared spectroscopy monitoring device is installed after the exhaust homogenization section and before the die head of the twin-screw extruder. This device monitors the intrinsic viscosity and characteristic functional group peak area ratio of the melt in real time and finely adjusts the temperature of the high-intensity shear dispersion section and the lateral liquid injection rate based on the feedback data, so that the melt flow rate of the final product is stabilized within the range of 5-15 g / 10min.

4. The method for preparing a cold-resistant thermoplastic polyurethane cable material according to claim 1, characterized in that, The number average molecular weight of the propylene glycol adipate polyester is 2000-4000 g / mol, and the pour point of the trioctyl trimellitate is below -50℃. Both need to be dehydrated at 100-120℃ and vacuum degree -0.095MPa for 2-4 hours before ultrasonic treatment.

5. A cold-resistant thermoplastic polyurethane cable material, characterized in that, The material is prepared using the method described in any one of claims 1 to 4 for a cold-resistant thermoplastic polyurethane cable.

Images