Fluorine-free efficient carbon-forming flame-retardant polyether polyurethane and preparation method thereof

Abstract

The present application relates to the field of polyurethane, in particular to a kind of fluorine-free high-efficiency carbon-forming flame-retardant polyether polyurethane and preparation method thereof.Flame-retardant polyether polyurethane includes the following components by mass fraction: thermoplastic polyether polyurethane matrix 75-87 parts, halogen-free fluorine-free catalytic carbon composite flame retardant 13-18 parts, functional additive 0-5 parts.The present application realizes high-efficiency flame retardation under very low addition amount through synergistic effect of phosphorus-nitrogen flame-retardant system and catalytic carbon system, only 13-18 parts of flame retardant addition amount is needed, 0.5-3.0mm wall thickness product can reach UL1581 VW-1 highest flame-retardant grade, completely no dripping, solve the industry pain point of traditional halogen-free flame-retardant system high addition amount, thin-wall flame-retardant substandard, rely on fluorine-containing additive anti-dripping, perfect adaptation to the flame-retardant demand of thin-wall product such as electric wire and cable.

Description

Technical Field

[0001] This invention relates to the field of polyurethane, specifically to a fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane and its preparation method. Background Technology

[0002] Polyether-type thermoplastic polyurethane (polyether TPU) is a typical thermoplastic elastomer material, composed of alternating soft segments made of polyether polyol and hard segments made of diisocyanate and small molecule chain extenders. This microphase separation structure of soft and hard segments endows the material with excellent comprehensive properties. Polyether TPU combines the high elasticity and flexibility of rubber with the processability of plastics, while also possessing excellent hydrolysis resistance, tear resistance, abrasion resistance, and low-temperature resistance. It is widely used in many core fields such as wire and cable, electronics, automotive manufacturing, aerospace, and rail transportation. Especially in the field of wire and cable sheathing, its excellent hydrolysis resistance and flexibility make it a core substrate for high-end cables.

[0003] However, polyether TPU has a limiting oxygen index of only 16%-18%, making it an extremely flammable polymer material. Its combustion process presents significant technical challenges: First, it undergoes a violent free radical chain reaction during combustion, resulting in a rapid heat release rate and rapid fire spread. Second, the material undergoes severe melting during combustion, accompanied by the generation of a large number of flammable droplets. These droplets carry active free radicals and flammable small molecules, which can easily ignite surrounding combustibles, causing secondary fires and significantly increasing the fire risk. Third, traditional flame-retardant modification methods severely degrade the core performance of polyether TPU, limiting its application in fields with high fire safety requirements.

[0004] Currently, flame retardant modification of polyether TPU is mainly divided into two categories: chemical copolymerization modification and physical filler modification. Chemical copolymerization modification involves introducing flame-retardant groups, such as those containing phosphorus or nitrogen, into the main chain or side chain of the molecule during the polyurethane polymerization process to achieve flame retardant function. This method has a long-lasting flame retardant effect and minimal impact on material properties, but it suffers from problems such as complex polymerization processes, high requirements for production equipment, poor flexibility in adjusting product grades, and extremely high production costs. It can only be applied in small batches in a few high-end fields and cannot achieve large-scale industrial promotion.

[0005] Physical filler modification is currently the mainstream technical solution in the industry. By adding flame retardants during the processing of polyether TPU, the flame retardant performance is improved. This method is simple, cost-controllable, and flexible in formula adjustment, making it suitable for large-scale industrial production. However, existing filler modification solutions have many technical defects that are difficult to solve: (1) Halogenated flame retardant system: With bromine-antimony flame retardants as the core, the flame retardant efficiency is high and the impact on the mechanical properties of the material is small. It is usually combined with Teflon (polytetrafluoroethylene) to achieve anti-dripping effect. However, when this system burns, it releases a large amount of toxic and corrosive gases and highly toxic dioxins, which seriously endanger the environment and human health. With the increasingly strict global environmental regulations such as RoHS and REACH, its use has been restricted or prohibited in many fields. Halogen-free and fluorine-free has become an inevitable trend in the industry. (2) Conventional halogen-free flame retardant system: It is based on phosphorus and nitrogen intumescent flame retardants and metal hydroxides. It is environmentally friendly, but has fatal defects: First, the flame retardant efficiency is extremely low. It requires a high addition of 28-35% to achieve the basic flame retardant effect. However, high filling will cause the core mechanical properties of polyether TPU, such as flexibility, tensile strength and elongation at break, to drop significantly, completely losing its high elasticity material advantage. At the same time, it seriously deteriorates the processing fluidity of the material. Second, the carbonization effect is poor and it cannot effectively suppress the generation of melt droplets. It usually requires the addition of fluorine-containing additives such as Teflon to achieve anti-dripping. However, fluorine-containing additives have poor compatibility with polyurethane substrates and are prone to migration and precipitation, affecting the appearance, electrical properties and long-term performance of the product. At the same time, it does not meet the requirements of fluorine-free environmental protection. Third, the flame retardant performance of thin-walled products is poor. Usually, the wall thickness of the product needs to reach more than 6mm to pass the UL1581 VW-1 flame retardant test. It cannot meet the flame retardant requirements of thin-walled products such as wires and cables, and the application scenarios are severely limited.

[0006] Therefore, developing a halogen-free and fluorine-free flame-retardant polyurethane material with high flame-retardant efficiency, excellent thin-wall flame-retardant properties, no dripping, and excellent maintenance of the core mechanical and processing properties of polyether TPU is a technical challenge that urgently needs to be overcome in the industry, and it has important economic value and social significance. Summary of the Invention

[0007] To address the core shortcomings of existing flame-retardant polyether polyurethane technologies, such as environmental unfriendliness due to halogen and fluorine content, high flame retardant dosage, significant loss of mechanical properties, failure to meet flame retardancy standards for thin-walled polyurethanes, easy dripping during combustion, and easy precipitation of additives, one objective of this invention is to provide a fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane. This material is completely halogen-free and fluorine-free, environmentally compliant, and achieves a UL1581 VW-1 flame retardancy rating with a 2.0mm thin wall thickness, completely suppressing dripping. Simultaneously, it excellently retains the core properties of polyether TPU, such as high elasticity, high toughness, hydrolysis resistance, and aging resistance, exhibiting excellent processing performance and adaptability to various molding processes. Another objective of this invention is to provide a method for preparing this fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane. This preparation method is simple, compatible with existing industrial production equipment, has high production efficiency, good batch stability, and can achieve large-scale mass production.

[0008] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention discloses a fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane, comprising the following components by mass parts: 75-87 parts of thermoplastic polyether polyurethane matrix, 13-18 parts of halogen-free and fluorine-free catalytic carbonization composite flame retardant, and 0-5 parts of functional additives.

[0009] Preferably, the thermoplastic polyether polyurethane matrix is ​​an alternating block copolymer composed of polyether polyol soft segments, diisocyanate, and chain extender, with a Shore hardness of 85A-95A.

[0010] Preferably, the thermoplastic polyether polyurethane matrix is ​​a polyether-type thermoplastic polyurethane prepared by polymerizing tetrahydrofuran to obtain polytetrahydrofuran ether polyol as the soft segment. This type of substrate has superior hydrolysis resistance, low-temperature flexibility, and mechanical properties, and is the mainstream substrate in the fields of wires and cables.

[0011] Preferably, the functional additive is one or more of antioxidants, dispersants, and hydrolysis-resistant agents.

[0012] Preferably, the halogen-free and fluorine-free catalytic carbon-forming composite flame retardant comprises, by weight parts: The composition consists of 90-98 parts of phosphorus-nitrogen flame-retardant composite, 0.5-5 parts of modified inorganic particles, 0.5-3 parts of surface-modified coupling agent, and 0-3 parts of reinforcing additive.

[0013] Preferably, the phosphorus-nitrogen flame retardant composite component comprises aluminum hypophosphite, piperazine, dimethyl diphenylphosphine (DMDP), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in a mass ratio of (2-4):(0.5-1.5):(0.3-0.8):(0.05-0.2).

[0014] More preferably, the mass ratio of aluminum hypophosphite, piperazine, DMDP, and DOPO is 3:1:0.5:0.1.

[0015] Among them, aluminum hypophosphite is a high-phosphorus flame retardant that combines gas-phase and condensed-phase flame retardant effects. Upon thermal decomposition, it releases free radicals such as PO· and HPO·, which capture highly reactive hydroxyl and alkoxy free radicals in the combustion chain reaction, terminating the gas-phase combustion reaction. Simultaneously, the metaphosphoric acid substances generated during decomposition promote dehydration and charring of the substrate, forming a dense carbon layer. Piperazine is a high-nitrogen flame retardant that, upon thermal decomposition, releases inert gases such as nitrogen and ammonia, diluting the concentration of combustible gases and oxygen, reducing the combustion reaction rate. It also synergistically forms a phosphorus-nitrogen expansion flame retardant system with phosphorus-based components, improving charring efficiency. DMDP and DOPO are organophosphorus flame retardants with good compatibility with polyurethane substrates, improving the dispersibility of the flame retardant system in the substrate. They also supplement phosphorus-based flame retardant components, enhancing free radical capture and charring effects, and reducing the impact on the material's mechanical properties. By blending these four components in specific proportions, a high-phosphorus, high-nitrogen component design is achieved, balancing gas-phase and condensed-phase flame retardant effects while maintaining flame retardant efficiency and substrate compatibility.

[0016] Preferably, the modified inorganic particles are ultrafine silica particles modified by hydrolysis at temperatures above 1000℃, with a particle size of 0.5-2μm.

[0017] More preferably, the modified inorganic particles have a particle size of 1 μm.

[0018] The preparation method of the halogen-free and fluorine-free catalytic carbonization composite flame retardant includes the following steps: S1. Surface modification of modified inorganic particles: The modified inorganic particles are vacuum dried to remove surface adsorbed water, and then a surface modification coupling agent is added. The particles are then mixed at high speed under heating conditions to carry out surface modification treatment, so that the coupling agent is fully grafted onto the surface of the inorganic particles to obtain modified inorganic particles. S2. Compounding and homogenization treatment: Add each raw material of the phosphorus-nitrogen flame retardant composite component into the mixing equipment according to the ratio, premix evenly, add the modified inorganic particles obtained in step S1, add the reinforcing additives, continue high-speed mixing until the system is completely homogeneous, and after discharge, the halogen-free flame retardant of polyester polyether with catalytic carbonization is obtained.

[0019] Preferably, in step S1, the vacuum drying temperature is 110-130℃ and the drying time is 1-3h; the surface modification treatment temperature is 70-90℃, the mixing speed is 300-500rpm, and the mixing time is 10-20min.

[0020] Preferably, in step S2, the premixing speed is 300-500 rpm and the mixing time is 3-8 min; the subsequent mixing speed is 300-500 rpm and the mixing time is 8-15 min, and the mixing temperature is controlled at 40-60℃ to avoid thermal decomposition of the raw materials.

[0021] After high-temperature hydrolysis modification, silicon dioxide particles develop defects or dislocations in their crystal structure, causing the grains to carry a negative charge and generate strong polarity. This results in a white, porous, ultrafine, and non-agglomerated amorphous structure with a trioctahedral three-layer structure, while also containing trace amounts of aluminum, sodium, potassium, iron, magnesium, and other ions.

[0022] Preferably, the surface-modifying coupling agent is an aminosilane coupling agent, and the amount added is 0.8-1.2% of the total mass of the flame retardant powder.

[0023] Preferably, the surface-modifying coupling agent is one or more of KH-550, KH-792, and KH-602.

[0024] Preferably, the reinforcing agent is an antioxidant.

[0025] Secondly, this invention discloses a method for preparing a fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane, comprising the following steps: (1) Raw material drying pretreatment: Place the thermoplastic polyether polyurethane matrix in an oven with ventilation function and dry it at 80℃ for 2-4 hours to fully remove the adsorbed moisture in the raw material and avoid performance degradation caused by hydrolysis of the raw material during processing. After drying, seal it for later use. (2) Ingredient homogenization and mixing: The dried thermoplastic polyether polyurethane matrix, halogen-free and fluorine-free catalytic carbon composite flame retardant and functional additives are added to a high-speed mixer according to the formula. The mixture is stirred at high speed at room temperature until the system is completely homogeneous to obtain the premix. (3) Melt extrusion granulation: The premixed material is added to a twin-screw extruder and processed using a low-shear melt extrusion process. After the material is melt-blended and homogenized, it is extruded from the die head, cooled by a water cooling tank, stretched, and granulated by a pelletizer to obtain the fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane particles.

[0026] Preferably, in step (2), the speed of high-speed stirring is 300-500 rpm and the stirring time is 3-8 min to ensure that the components are mixed evenly and to avoid the temperature rise of the material caused by high-speed stirring.

[0027] Preferably, in step (3), the temperature of the twin-screw extruder is set as follows: 145-155℃ for the first section, 190-210℃ for the second to eighth sections, and 185-195℃ for the ninth section; the screw speed is controlled at 200-350 rpm.

[0028] Preferably, the flame-retardant polyether polyurethane particles obtained in step (3) can be dried at 80°C for 2-3 hours and then processed by conventional thermoplastic processing techniques such as injection molding and extrusion molding to prepare various flame-retardant products such as wire and cable sheaths, electronic and electrical structural parts, automotive interior parts, and aerospace parts.

[0029] The beneficial effects of this invention are as follows: 1. The flame-retardant polyether polyurethane of the present invention is completely free of halogens, Teflon and heavy metals. No toxic or corrosive gases or dioxins are produced during combustion, and no fluorine is released. It meets environmental protection standards, is suitable for the application needs of high-end environmentally friendly products, and conforms to the industry's trend of halogen-free and fluorine-free development.

[0030] 2. This invention achieves highly efficient flame retardancy with extremely low addition amounts through the synergistic effect of phosphorus-nitrogen flame retardant system and catalytic carbonization system. Only 13-18 parts of flame retardant are needed to enable products with a wall thickness of 2.0mm to reach the highest flame retardancy rating of UL1581 VW-1. At the same time, it completely inhibits the generation of combustion dripping, solving the industry pain points of high addition amount, failure to meet the flame retardancy standards for thin-walled products, and reliance on fluorinated additives to prevent dripping in traditional halogen-free flame retardant systems. It is perfectly suited to the flame retardancy requirements of thin-walled products such as wires and cables.

[0031] 3. The flame retardant system of the present invention has a low addition amount and achieves good interfacial compatibility with the polyurethane matrix through surface modification. The loss rate of core mechanical properties of polyether TPU, such as tensile strength, elongation at break, flexibility, and tear resistance, is less than 15%, and the inherent characteristics of high elasticity and high toughness of polyether TPU are fully preserved. At the same time, it does not affect the original excellent hydrolysis resistance and aging resistance of the substrate, and can meet the use requirements of humid environment and long-term service, thus taking into account both flame retardant performance and material performance.

[0032] 4. This invention modifies the surface of inorganic particles using a quaternary ammonium siloxane coupling agent, enabling the flame retardant components to achieve uniform nanoscale dispersion in the polyurethane matrix without agglomeration and with strong interfacial bonding. During long-term thermal aging and damp heat aging, there is no migration or precipitation of flame retardant, ensuring the long-term stability of the product's appearance, mechanical properties, and electrical properties, and extending the product's service life.

[0033] 5. The flame-retardant polyether polyurethane of the present invention has a simple preparation process, requires no special equipment, and can be directly produced and molded on existing conventional thermoplastic processing equipment such as twin-screw extruders, injection molding machines, and cable extruders without the need for equipment modification; the addition of the flame-retardant system does not degrade the thermoplastic processing performance of polyether TPU, the material has good melt flowability, a wide processing window, high molding efficiency, and good batch stability of products, which can realize large-scale industrial mass production.

[0034] 6. The amount of flame retardant added in this invention is much lower than that in traditional halogen-free flame retardant systems, which significantly reduces the raw material cost of flame retardant modification. At the same time, the material has excellent processing and mechanical properties, and there is no problem of increased defect rate during production. The overall production cost is more than 20% lower than that of existing flame retardant polyether polyurethane systems, giving it strong market competitiveness and promotional value.

[0035] 7. The flame retardant system of the present invention enables the modified polyether TPU to achieve an oxygen index of 30%-34. Detailed Implementation

[0036] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0037] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0038] In the following examples and comparative examples, all raw materials used are commercially available industrial-grade products, as detailed below: Polyether TPU-1: Shore hardness 85A, polytetrahydrofuran ether type, commercially available industrial grade; Polyether TPU-2: Shore hardness 95A, polytetrahydrofuran ether type, commercially available industrial grade; Conventional halogen-free flame retardant: an intumescent flame retardant with an APP / MPP ratio of 3:1, commercially available industrial grade; Teflon micron powder: a commercially available industrial-grade anti-dripping agent; Functional additives: Antioxidant 1010, Antioxidant 168, and polycarbodiimide hydrolysis resistant agent are all commercially available industrial grade.

[0039] The present invention will be further described below with reference to the following embodiments.

[0040] Example 1 A fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane, with the following components by mass parts: 82 parts of polyether TPU-1, 16 parts of halogen-free and fluorine-free catalytic carbonization composite flame retardant, and 2 parts of functional additives (0.3 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of hydrolysis resistant agent).

[0041] The halogen-free and fluorine-free catalytic carbonization composite flame retardant has the following components by mass: 96.2 parts of phosphorus-nitrogen flame retardant composite component, of which aluminum hypophosphite, piperazine, DMDP, and DOPO are in a mass ratio of 3:1:0.5:0.1, including 72 parts of aluminum hypophosphite, 24 parts of piperazine, 12 parts of DMDP, and 2.4 parts of DOPO; 0.8 parts of modified inorganic particles; 1.0 part of aminosilane coupling agent; and 2.0 parts of reinforcing additives (0.5 parts of antioxidant 1010).

[0042] The preparation method of halogen-free and fluorine-free catalytic carbonization composite flame retardant includes the following steps: S1 Surface modification of modified inorganic particles: The modified inorganic particles were vacuum dried at 120℃ for 2h, and then added to a high-speed mixer with aminosilane coupling agent KH-550. The mixture was mixed at 80℃ and 350rpm for 15min to complete the surface modification and obtain the modified inorganic particles. The modified inorganic particles are ultrafine silica particles modified by high-temperature hydrolysis above 1000℃ with a particle size of 1μm.

[0043] S2 Compound Homogenization Treatment: Add aluminum hypophosphite, piperazine, DMDP, and DOPO to a high-speed mixer according to the ratio, premix at 350 rpm for 5 min, then add the modified inorganic particles obtained in step S1, then add the reinforcing additives, and continue mixing at 350 rpm for 10 min. The mixing temperature is controlled at 50℃. After discharge, a halogen-free flame retardant is obtained.

[0044] The preparation method of flame-retardant polyether polyurethane includes the following steps: (1) Raw material drying pretreatment: Place polyether TPU-1 in an oven with ventilation function and dry it at 80°C for 3 hours to remove moisture. After drying, seal it for later use. (2) Ingredient homogenization and mixing: According to the ratio, the dried polyether TPU-1, halogen-free and fluorine-free catalytic carbon composite flame retardant and functional additives are added to a high-speed mixer and stirred at 350 rpm for 5 minutes at room temperature to obtain a premix. (3) Melt extrusion granulation: The premixed material is added to a twin-screw extruder and melt extruded using a low-shear process. The temperature of each section of the twin screw is set as follows: 150℃ for the first section, 195℃ for the second section, 205℃ for the third to seventh sections, 200℃ for the eighth section, and 190℃ for the ninth section. The screw speed is 300 rpm, and only one 90-degree shear module is installed in the screw. After melt blending, the material is extruded from the die head, cooled by a water cooling tank, stretched, and granulated to obtain flame-retardant polyether polyurethane particles.

[0045] Example 2 A fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane, with the following components by mass parts: 85 parts of polyether TPU-1, 13 parts of halogen-free and fluorine-free catalytic carbonization composite flame retardant, and 2 parts of functional additives (0.3 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of hydrolysis resistant agent).

[0046] The preparation methods of the halogen-free and fluorine-free catalytic carbonization composite flame retardant and the flame-retardant polyether polyurethane in this embodiment are completely consistent with those in Example 1.

[0047] Example 3 The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane of this embodiment has the following components by mass parts: 80 parts of polyether TPU-1, 18 parts of halogen-free and fluorine-free catalytic carbonization composite flame retardant, and 2 parts of functional additives (0.3 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of hydrolysis resistant agent).

[0048] The preparation methods of the halogen-free and fluorine-free catalytic carbonization composite flame retardant and the flame-retardant polyether polyurethane in this embodiment are completely consistent with those in Example 1.

[0049] Example 4 The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane of this embodiment has the following components by mass parts: 82 parts of polyether TPU-2, 16 parts of halogen-free and fluorine-free catalytic carbonization composite flame retardant, and 2 parts of functional additives (0.3 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of hydrolysis resistant agent).

[0050] The preparation methods of the halogen-free and fluorine-free catalytic carbonization composite flame retardant and the flame-retardant polyether polyurethane in this embodiment are completely consistent with those in Example 1.

[0051] Example 5 The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane of this embodiment has the following components by mass parts: 83 parts of polyether TPU-1, 15 parts of halogen-free and fluorine-free catalytic carbonization composite flame retardant, and 2 parts of functional additives (0.3 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of hydrolysis resistant agent).

[0052] The preparation methods of the halogen-free and fluorine-free catalytic carbonization composite flame retardant and the flame-retardant polyether polyurethane in this embodiment are completely consistent with those in Example 1.

[0053] Comparative Example 1 This comparative example is pure polyether TPU, with the following components: 98 parts of polyether TPU-1 and 2 parts of functional additives. The only difference between this example and Example 1 is that no halogen-free and fluorine-free catalytic carbonization composite flame retardant is added. This example serves as a blank control group.

[0054] Comparative Example 2 This comparative example is a conventional halogen-free flame-retardant polyether polyurethane, with the following components: 68 parts of polyether TPU-1, 30 parts of conventional halogen-free flame retardant, and 2 parts of functional additives. The only difference between this example and Example 1 is that the halogen-free and fluorine-free catalytic carbonization composite flame retardant is replaced with a conventional halogen-free flame retardant.

[0055] Comparative Example 3 This comparative example is a fluorinated halogen-free flame-retardant polyether polyurethane, with the following components: 78 parts of polyether TPU-1, 20 parts of conventional halogen-free flame retardant, 2 parts of Teflon micro powder, and 0 parts of functional additives. The only difference between this preparation method and Example 1 is that the halogen-free and fluorine-free catalytic carbonization composite flame retardant is replaced with a conventional halogen-free flame retardant.

[0056] Comparative Example 4 The flame-retardant polyether polyurethane in this comparative example differs from that in Example 1 only in that the flame retardant used does not contain modified inorganic particles, while the other components and preparation methods are the same as in Example 1.

[0057] Performance testing The polyurethane particles prepared in Examples 1-5 and Comparative Examples 1-4 were dried in an oven at 80°C for 3 hours, and then injection molded into standard test strips. After being placed in a standard environment for 24 hours, various performance tests were conducted according to the following standards: 1. Flame retardant performance: UL1581 vertical burning test, sample thickness 2.0mm, test according to UL1581 standard, record flame retardant rating and dripping condition; Limiting oxygen index (LOI) test according to GB / T 2406.2-2009 standard.

[0058] 2. Mechanical properties: Tensile strength and elongation at break were tested according to GB / T 528-2009 standard, using dumbbell-shaped specimens and a tensile rate of 500 mm / min; Shore hardness was tested according to GB / T 531.1-2008 standard.

[0059] 3. Hydrolysis resistance: In accordance with GB / T 2573-2008 standard, the sample was placed in a damp heat aging chamber at 80℃ and 95% relative humidity for 168h, and the tensile strength retention rate after aging was tested.

[0060] 4. Hot air aging performance: In accordance with GB / T 3512-2014 standard, the sample was placed in a 100℃ hot air aging chamber for 168 hours and the tensile strength retention rate after aging was tested.

[0061] 5. Precipitation performance test: The injection-molded sample was placed in an 80℃ oven for 72 hours for heat treatment. After taking it out, the sample surface was observed to see if there was any powder precipitation. At the same time, the surface energy test was used to characterize the precipitation.

[0062] 6. Processing fluidity: Melt flow rate (MFR) was tested using a melt flow indexer at 190℃ / 5kg, in accordance with GB / T 3682-2018 standard.

[0063] 7. Environmental performance: The halogen and fluorine content is tested by ion chromatography, and the content of restricted substances is tested in accordance with RoHS 2.0 standard.

[0064] The results of the various performance tests are shown in the table below:

[0065] The test results above show that: 1. The flame-retardant polyether polyurethanes of Examples 1-5 of this invention, with a low flame retardant addition of 13-18 parts, can achieve a UL1581 V-0 rating or higher for 2.0 mm wall thickness samples. Among them, an addition of more than 15% can achieve the highest VW-1 flame retardant rating, and there is no combustion dripping at all. The oxygen index is over 30%, which is far superior to the pure TPU of Comparative Example 1 and the conventional halogen-free flame retardant systems of Comparative Examples 2 and 4. It perfectly solves the problems of flammability and easy dripping of polyether TPU.

[0066] 2. The flame-retardant polyether polyurethane of the present invention has minimal impact on the mechanical properties of the substrate. The tensile strength retention rate of Example 1 exceeds 90%, and the elongation at break retention rate is close to 90%, which is far superior to the high-addition flame-retardant systems of Comparative Example 2 and Comparative Example 3. It fully retains the core characteristics of high elasticity and high toughness of polyether TPU. At the same time, the melt flow rate of the material is close to that of pure TPU, with excellent processing fluidity and no processing deterioration problems.

[0067] 3. The flame-retardant polyether polyurethane of the present invention has excellent hydrolysis resistance and aging resistance. The tensile strength retention rate after wet heat aging and hot air aging is basically the same as that of pure TPU, which is far superior to the traditional high-filler flame-retardant system and can meet the requirements of long-term service.

[0068] 4. The flame-retardant polyether polyurethane of the present invention has excellent compatibility with the substrate and no precipitation after heat aging, while the system with added Teflon in Comparative Example 3 showed serious precipitation, which could not meet the appearance and performance requirements of the product for long-term use; at the same time, the present invention is completely halogen-free and fluorine-free, which meets the environmental protection requirements.

[0069] 5. Comparative Example 4, without the addition of catalytic carbon-forming inorganic particles, failed to achieve effective flame retardancy and anti-dripping even with the addition of the same phosphorus-nitrogen flame retardant components, demonstrating the synergistic effect of catalytic carbon-forming inorganic particles and the phosphorus-nitrogen flame retardant system.

[0070] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane, characterized in that, By mass parts, it includes the following components: 75-87 parts of thermoplastic polyether polyurethane matrix, 13-18 parts of halogen-free and fluorine-free catalytic carbonization composite flame retardant, and 0-5 parts of functional additives. The thermoplastic polyether polyurethane matrix is ​​an alternating block copolymer composed of polyether polyol soft segments, diisocyanate, and chain extender.

2. The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 1, characterized in that, The functional additives are one or more of antioxidants, dispersants, and hydrolysis-resistant agents.

3. The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 1, characterized in that, The halogen-free and fluorine-free catalytic carbon-forming composite flame retardant comprises, by mass parts: The composition consists of 90-98 parts of phosphorus-nitrogen flame-retardant composite, 0.5-5 parts of modified inorganic particles, and 0.5-3 parts of surface-modified coupling agent.

4. The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 3, characterized in that, The phosphorus-nitrogen flame-retardant composite component comprises aluminum hypophosphite, piperazine, dimethyl diphenylphosphine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in a mass ratio of (2-4):(0.5-1.5):(0.3-0.8):(0.05-0.2).

5. The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 3, characterized in that, The modified inorganic particles are ultrafine inorganic particles modified by high-temperature hydrolysis at temperatures above 1000℃, with a particle size of 0.5-2μm.

6. The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 3, characterized in that, The surface-modifying coupling agent is an aminosilane coupling agent, and the addition amount is 0.8-1.2% of the total mass of the flame retardant powder; the surface-modifying coupling agent is one or more of KH-550, KH-792, and KH-602.

7. The fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 3, characterized in that, The enhancing agent is one or more antioxidants.

8. A method for preparing the fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 1, characterized in that, Includes the following steps: (1) Raw material drying pretreatment: Place the thermoplastic polyether polyurethane matrix in an oven with ventilation function and dry it at 80℃ for 2-4 hours to fully remove the adsorbed moisture in the raw material and avoid performance degradation caused by hydrolysis of the raw material during processing. After drying, seal it for later use. (2) Ingredient homogenization and mixing: The dried thermoplastic polyether polyurethane matrix, halogen-free and fluorine-free catalytic carbon composite flame retardant and functional additives are added to a high-speed mixer according to the formula. The mixture is stirred at high speed at room temperature until the system is completely homogeneous to obtain the premix. (3) Melt extrusion granulation: The premixed material is added to a twin-screw extruder and processed using a low-shear melt extrusion process. After the material is melt-blended and homogenized, it is extruded from the die head, cooled by a water cooling tank, stretched, and granulated by a pelletizer to obtain the fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane particles.

9. The preparation method of a fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 1, characterized in that, In step (2), the speed of high-speed stirring is 300-500 rpm and the stirring time is 3-8 min.

10. The preparation method of a fluorine-free, high-efficiency carbon-forming flame-retardant polyether polyurethane according to claim 1, characterized in that, In step (3), the temperature of the twin-screw extruder is set as follows: 145-155℃ for the first section, 190-210℃ for the second to eighth sections, and 185-195℃ for the ninth section; the screw speed is controlled at 200-350 rpm.

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