Highly flame retardant elastomer composite and its use in special cables

Abstract

This invention discloses a high flame-retardant elastomer composite material and its application in special cables, belonging to the technical field of polymer composite materials and cable materials. The composite material comprises, by weight, 100 parts of matrix resin, 60-120 parts of composite flame retardant, 15-40 parts of plasticizer, 1-5 parts of antioxidant, and 2-8 parts of crosslinking agent. The matrix resin is a blend of polyether-type thermoplastic polyurethane and ethylene-vinyl acetate copolymer. The composite flame retardant is a core-shell structure inorganic flame retardant, with a core of nano-zinc hydroxystannate and a shell of magnesium hydroxide, and the surface is modified by a double wet process using a composite silane coupling agent and calcium stearate. The material of this invention meets the UL1581 VW-1 and IEC 60332-3-22 FT4 flame retardant ratings, has an elongation at break ≥350%, and can withstand 1000 temperature cycles from -40℃ to 150℃ without cracking, exhibiting excellent overall performance and suitable for high flame-retardant flexible special cables.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials and cable engineering technology, specifically relating to a high flame-retardant elastomer composite material and its application in special cables. Background Technology

[0002] With the rapid development of high-end equipment industries such as new energy vehicles and energy storage systems, higher performance requirements have been placed on their supporting special cables. These cables not only need excellent flexibility and resistance to high and low temperatures, but also need to meet stringent high flame-retardant ratings to meet the safety protection needs of confined spaces such as vehicle interiors and energy storage compartments. The flame-retardant properties of cables directly affect the speed of fire spread and are of great significance to ensuring the safety of personnel and property.

[0003] Currently, the insulation and sheathing layers of special cables mostly use thermoplastic elastomer materials, such as polyurethane (TPU) and ethylene-vinyl acetate copolymer (EVA). Among them, TPU has excellent elasticity, abrasion resistance, and low-temperature resistance, but its flame retardant properties are poor, making it difficult to meet the flame retardant requirements of high-end applications. EVA has good processing performance, low cost, and is easy to combine with flame retardants, but when used alone, its elasticity and high and low temperature stability are insufficient, making it unsuitable for applications such as high-voltage wiring harnesses in new energy vehicles that require frequent bending and withstand extreme temperature changes.

[0004] To improve the flame retardant properties of elastomer materials, existing technologies typically employ the addition of inorganic flame retardants. However, using a single inorganic flame retardant presents challenges such as high dosage requirements and poor compatibility with the matrix resin. Excessive flame retardant dosage (usually exceeding 150 parts) degrades the material's elasticity and processing properties, resulting in an elongation at break below 150%, increased brittleness, and susceptibility to cracking, failing to meet the flexibility requirements of cables. Insufficient dosage, on the other hand, makes it difficult to meet high-end flame retardant standards.

[0005] Furthermore, existing inorganic flame retardants are mostly modified using a single silane coupling agent, which has limited modification effects. The flame retardants are prone to uneven dispersion and agglomeration in the matrix resin, which not only reduces the synergistic flame retardant efficiency but also further impairs the mechanical properties and flexibility of the material. Simultaneously, in conventional preparation processes, flame retardants are susceptible to high shear stress, resulting in structural damage and a decline in flame retardant efficacy.

[0006] Existing technologies have attempted to construct core-shell structured flame retardants to enhance synergistic effects. For example, CN114479183A discloses an organically modified zinc hydroxystannate-hypophosphite flame retardant, which uses zinc hydroxystannate as the core, hypophosphite as the shell, and melamine-formaldehyde resin as the surface coating layer, suitable for flame retardancy and smoke suppression of PVC resin. However, the rigid organic coating layer used in this scheme has poor compatibility with flexible matrices such as TPU / EVA, and does not consider the integrity protection of the flame retardant structure during processing under high filling conditions, making it difficult to apply to highly flexible special cable materials.

[0007] Therefore, developing an elastomer composite material with high flame retardancy, excellent elasticity, good high and low temperature stability, and excellent processing performance, as well as corresponding preparation methods and special cables, to meet the application needs of high-end scenarios such as new energy vehicles and energy storage systems has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a high flame-retardant elastomer composite material that achieves excellent flame-retardant effect without sacrificing flexibility by synergistically designing a polymer matrix, a surface-modified inorganic flame-retardant system, and a low-migration plasticizing system, and is suitable for the manufacture of special cables.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A high flame-retardant elastomer composite material, by weight, comprises the following components: 100 parts of matrix resin, 60-120 parts of composite flame retardant, 15-40 parts of plasticizer, 1-5 parts of antioxidant, and 2-8 parts of crosslinking agent; The matrix resin is a blend of polyether thermoplastic polyurethane (TPU) and ethylene-vinyl acetate copolymer (EVA), wherein the mass ratio of TPU to EVA is 1:(0.3-0.8). The composite flame retardant is an inorganic composite flame retardant with a core-shell structure. Its core is nano-zinc hydroxystannate, and its shell is magnesium hydroxide coated by chemical deposition. The surface of the composite flame retardant is subjected to dual wet modification treatment with composite silane coupling agent and calcium stearate.

[0010] This invention achieves synergistic complementarity of TPU and EVA by rationally proportioning the two materials. TPU possesses excellent elasticity and low-temperature resistance, while EVA enhances the material's processing performance and compatibility with flame retardants. The two are blended at a mass ratio of 1:(0.3-0.8), enabling the matrix resin to simultaneously possess good elasticity, processability, and high and low temperature stability.

[0011] The composite flame retardant adopts a core-shell structure design. The core nano-zinc hydroxystannate has excellent smoke suppression and flame retardant synergistic effects, while the outer shell magnesium hydroxide has good heat absorption and flame retardant effects. The two are combined by chemical deposition to form a core-shell structure, which can achieve synergistic flame retardant effect and significantly improve the flame retardant performance of the composite material. At the same time, the compatibility between the composite flame retardant and the matrix resin is significantly improved by the dual wet modification treatment of composite silane coupling agent and calcium stearate.

[0012] Furthermore, the TPU is a polytetrahydrofuran ether diol type thermoplastic polyurethane with a hardness of 80A-95A; the vinyl acetate (VA) content in the EVA is 28%-40%. Polytetrahydrofuran ether diol type TPU has superior hydrolysis resistance and high / low temperature resistance; the hardness controlled at 80A-95A gives the composite material good elasticity and resistance to deformation; the VA content in the EVA is controlled at 28%-40%, ensuring both the material's flexibility and processing performance, while also improving its compatibility with flame retardants and other additives.

[0013] Furthermore, the particle size of the composite flame retardant is D50≤1.5μm and D97≤3.0μm; in the core-shell structure, the mass ratio of the core nano-zinc hydroxystannate to the shell magnesium hydroxide is (1:2-5). Controlling the particle size of the composite flame retardant within the above range improves its dispersion uniformity in the matrix resin and reduces its impact on the material's mechanical properties; controlling the core-shell mass ratio at 1:(2-5) optimizes the synergistic effect of the core's smoke suppression and flame retardancy and the shell's heat absorption and flame retardancy, ensuring that the composite material meets high-end flame retardant standards.

[0014] Furthermore, the composite silane coupling agent is a mixture of vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 1:(0.5-1.5); and the surface of the composite flame retardant is synergistically modified by the composite silane coupling agent and calcium stearate. Vinyltrimethoxysilane can chemically react with the matrix resin to enhance the bonding force between the flame retardant and the matrix; γ-aminopropyltriethoxysilane can improve the surface polarity of the flame retardant and enhance its compatibility with the matrix resin. The two are compounded in a mass ratio of 1:(0.5-1.5) and then synergistically modified with calcium stearate using a dual wet process to achieve a synergistic effect of modification, which can further improve the dispersibility and compatibility of the flame retardant.

[0015] Further, the plasticizer is at least one of trioctyl trimellitate (TOTM) or di(2-ethylhexyl) adipate (DOA); the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a 1:1 mass ratio; the crosslinking agent is at least one of dicumyl peroxide (DCP) or triallyl isocyanurate (TAIC). TOTM and DOA both exhibit excellent plasticizing effects and high / low temperature resistance, improving the flexibility and processing performance of the composite material, and have good compatibility with the matrix resin and flame retardant. The 1:1 mixture of antioxidants 1010 and 168 achieves a synergistic effect of free radical capture and hydroperoxide decomposition, effectively delaying material aging and extending the material's service life. DCP and TAIC both have good crosslinking effects, improving the mechanical properties, wear resistance, and high / low temperature stability of the composite material.

[0016] Furthermore, the composite material also includes 0-10 parts of lubricant and 0-20 parts of reinforcing filler; the lubricant is at least one of stearic acid, calcium stearate, or paraffin wax; the reinforcing filler is surface-modified nano-calcium carbonate or fumed silica. The lubricant can further improve the processing performance of the material, reduce frictional resistance during processing, and prevent material sticking to the mold; the reinforcing filler enhances the mechanical strength and wear resistance of the composite material, and the surface-modified nano-calcium carbonate or fumed silica has good compatibility with the matrix resin.

[0017] A method for preparing the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: The core-shell structured nano-hydroxystannate zinc-magnesium hydroxide inorganic composite flame retardant powder is prepared into an aqueous suspension with a solid content of 10%-20%. A composite silane coupling agent composed of vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 1:(0.5-1.5) is added, and the mixture is reacted at 60-80℃ for 30-60 minutes. Then, the pH is adjusted to 8.0-9.0, calcium stearate is added, and the reaction is continued for 20-40 minutes. After spray drying, the activated composite flame retardant is obtained. S2. Matrix resin blending: TPU and EVA are melt-blended in an internal mixer at 110-130℃ in a certain proportion to obtain a matrix blend; S3. Mixing and granulation: The matrix blend obtained in step S2, the modified composite flame retardant, plasticizer, antioxidant and crosslinking agent obtained in step S1 are added to a twin-screw extruder for mixing in proportion. The screw speed is controlled at 300-600 rpm and the processing temperature is 140-170℃. After extrusion, cooling and pelletizing, high flame retardant elastomer composite material particles are obtained.

[0018] The preparation method is simple and reproducible. In step S1, by controlling the solid content of the suspension, reaction temperature and time, the double wet modification of the composite flame retardant is ensured to be uniform and sufficient, and the modification effect is stable and consistent, thereby improving the activation degree of the flame retardant. In step S2, the mixing temperature is controlled at 110-130℃ to ensure that TPU and EVA are fully melted. In step S3, controlling the screw speed and processing temperature can ensure that the components are fully mixed, while avoiding material degradation during processing.

[0019] Furthermore, in step S3, the twin-screw extruder adopts a meshing co-directional twin screw with a length-to-diameter ratio of (40-48):1 and is equipped with a side feed port. The modified composite flame retardant is added through the side feed port to avoid high shear force damaging the flame retardant coating structure.

[0020] A co-rotating twin-screw extruder with a length-to-diameter ratio of (40-48):1 is used to improve the mixing effect and ensure that the components are evenly dispersed. Modified composite flame retardants are added through the side feed port to avoid the flame retardants being subjected to excessive shear force when added through the main feed port, thereby protecting the integrity of the core-shell coating structure of the flame retardants and ensuring that their flame retardant synergistic effect is not affected.

[0021] A highly flame-retardant flexible special cable includes a conductor and an insulation layer and / or sheath layer covering the conductor. The insulation layer and / or sheath layer are made from the highly flame-retardant elastomer composite material described in any one of the preceding claims, through extrusion molding and processing using irradiation crosslinking or silane crosslinking processes. Using the highly flame-retardant elastomer composite material of this invention to prepare the cable's insulation layer and / or sheath layer, combined with extrusion molding, irradiation crosslinking, or silane crosslinking processes, gives the insulation layer and sheath layer excellent flame-retardant properties, elasticity, and high and low temperature stability, while also possessing good insulation properties and abrasion resistance, thus meeting the application requirements of special cables.

[0022] Furthermore, the cable is used in high-voltage wiring harnesses or battery connection cables of energy storage systems in new energy vehicles. The cable passes the UL 1581 VW-1 vertical burning test and the IEC 60332-3-22 FT4 bundled burning test, and shows no cracking after 1000 temperature cycles from -40℃ to 150℃.

[0023] The cable's flame-retardant properties and resistance to high and low temperatures meet the requirements of high-end applications such as high-voltage wiring harnesses in new energy vehicles and battery connection cables in energy storage systems, effectively improving the safety and reliability of equipment, reducing fire risks, and extending the cable's service life.

[0024] The beneficial effects of this invention are: 1. By constructing a core-shell structured composite flame retardant with zinc hydroxystannate as the core and magnesium hydroxide as the outer shell, cable samples prepared with a total addition amount of only 60-120 parts passed the UL 1581 VW-1 vertical burning test and the IEC 60332-3-22 FT4 bundled burning test. This system, through the synergistic effect of zinc hydroxystannate gas-phase free radical capture and magnesium hydroxide condensate phase endothermic water release, exhibits significantly higher flame retardant efficiency than a single magnesium hydroxide system with the same filling amount.

[0025] 2. A dual wet modification technique using a composite silane coupling agent and calcium stearate is employed to construct a flexible interface layer on the flame retardant surface, significantly improving the interfacial compatibility between the inorganic filler and the TPU / EVA matrix. The resulting composite material maintains an elongation at break ≥350% under high-filling conditions, exhibits no cracking during low-temperature embrittlement at -40℃, and retains ≥85% tensile strength and ≥80% elongation at break after 168 hours of hot air aging at 150℃, meeting long-term reliability requirements.

[0026] 3. This invention achieves the simultaneous satisfaction of FT4 flame retardant rating and elongation at break ≥350% under the condition of adding ≤120 parts of halogen-free flame retardant, breaking through the prejudice of traditional technology.

[0027] 4. The material has a Shore A hardness between 80 and 95A, excellent wear resistance, meets the requirements of millions of reciprocating bends in cable chain systems, and is suitable for highly flexible special cables.

[0028] 5. The material can be processed using conventional extrusion equipment, resulting in high production efficiency. It eliminates the need for rubber vulcanization processes, significantly reducing energy consumption and making it suitable for large-scale industrial production. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can understand it.

[0030] It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope defined by the claims should be included within the scope of protection of the present invention.

[0031] In the following examples, all raw materials used are commercially available conventional raw materials, wherein: TPU is polytetrahydrofuran ether diol type; EVA is a commercially available conventional product, and the VA content meets the requirements of the invention; in the composite silane coupling agent, A171 is vinyltrimethoxysilane, and KH550 is γ-aminopropyltriethoxysilane; the antioxidant is 1010 and 168 compounded in a 1:1 ratio; other additives are all commercially available conventional products; in Comparative Example 4, the flame retardant disclosed in patent CN114479183A is simulated, with zinc hydroxystannate as the core and aluminum hypophosphite as the shell, and the surface is coated with melamine-formaldehyde resin, and the remaining raw materials are the same as in the examples.

[0032] In this invention, unless otherwise specified, "parts" refers to parts by weight.

[0033] A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0034] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0035] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: Nano-sized zinc hydroxystannate and magnesium hydroxide are dispersed in deionized water at a mass ratio of 1:3. Magnesium hydroxide is coated onto the surface of zinc hydroxystannate by chemical deposition to obtain core-shell structured nano-zinc hydroxystannate-magnesium hydroxide composite flame retardant powder (D50=1.2μm, D97=2.8μm). The core-shell structured composite flame retardant powder is prepared into an aqueous suspension with a solid content of 15%, and the above-mentioned composite silane coupling agent is added. The mixture is reacted at 70℃ for 45 minutes. Then, the pH is adjusted to 8.5 with ammonia, calcium stearate is added, and the reaction is continued for 30 minutes. After spray drying (inlet temperature 220℃, outlet temperature 95℃), the activated composite flame retardant is obtained. S2. Matrix resin blending: TPU and EVA are melt-blended in an internal mixer at 120°C for 8 minutes in proportion to obtain a matrix blend; S3. Mixing and Granulation: The matrix blend obtained in step S2, the modified composite flame retardant, plasticizer, antioxidant, and crosslinking agent obtained in step S1 are added to a twin-screw extruder in proportion for mixing. The twin-screw extruder adopts a meshing co-directional twin screw with a length-to-diameter ratio of 44:1 and is equipped with a side feed port. The modified composite flame retardant is added through the side feed port. The processing temperature is controlled as follows: Zone 1 140℃, Zone 2 150℃, Zone 3 160℃, Zone 4 165℃, Die head 165℃, and screw speed 450rpm. After extrusion, cooling, and pelletizing, high flame-retardant elastomer composite material particles are obtained, denoted as S1.

[0036] A highly flame-retardant flexible special cable includes a conductor, an insulation layer, and a sheath layer. The sheath layer is made of the aforementioned composite material through extrusion molding and radiation cross-linking processes. This cable is used in high-voltage wiring harnesses or battery connection cables in energy storage systems of new energy vehicles. The specific preparation method involves drying S1 particles in a 90°C oven for 4 hours and then extruding them into 3×2.5mm diameter sheets using an extruder. 2 The cable sheath was extruded at a temperature of 155℃ and a linear speed of 35m / min. After cross-linking by irradiation with a 5MeV electron accelerator (absorbed dose of 120kGy), a high flame-retardant flexible special cable, denoted as C1, was obtained.

[0037] Example 2 A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (77 parts of TPU, 23 parts of EVA, TPU to EVA mass ratio 1:0.3), 80 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0038] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0039] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: Prepare an activated composite flame retardant according to the method in Example 1; S2. Matrix resin blending: TPU and EVA are melt-blended in an internal mixer at 120°C for 8 minutes in proportion to obtain a matrix blend; S3. Mixing and granulation: This is exactly the same as in Example 1, that is, the twin-screw extruder has an aspect ratio of 44:1, side feeding, and the same parameters such as processing temperature and screw speed. After extrusion, cooling and pelletizing, high flame-retardant elastomer composite material particles are obtained, which are denoted as S2.

[0040] A high flame-retardant flexible special cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a high flame-retardant flexible special cable, denoted as C2.

[0041] Example 3 A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (67 parts of TPU, 33 parts of EVA, TPU to EVA mass ratio 1:0.5), 100 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0042] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0043] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: exactly the same as in Example 1; S2. Matrix resin blending: TPU and EVA are melt-blended in an internal mixer at 120°C for 8 minutes in proportion to obtain a matrix blend; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, high flame retardant elastomer composite material particles are obtained, denoted as S3.

[0044] A high flame-retardant flexible special cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a high flame-retardant flexible special cable, denoted as C3.

[0045] Example 4 A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (56 parts of TPU, 44 parts of EVA, TPU to EVA mass ratio 1:0.8), 120 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0046] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0047] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: exactly the same as in Example 1; S2. Matrix resin blending: TPU and EVA are melt-blended in an internal mixer at 120°C for 8 minutes in proportion to obtain a matrix blend; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, high flame-retardant elastomer composite material particles are obtained, denoted as S4.

[0048] A high flame-retardant flexible special cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a high flame-retardant flexible special cable, denoted as C4.

[0049] Example 5 A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of composite flame retardant (core-shell mass ratio 1:2, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0050] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0051] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: Nano-sized zinc hydroxystannate and magnesium hydroxide are dispersed in deionized water at a mass ratio of 1:2. Magnesium hydroxide is coated on the surface of zinc hydroxystannate by chemical deposition to obtain core-shell structured nano-zinc hydroxystannate-magnesium hydroxide composite flame retardant powder (D50=1.2μm, D97=2.8μm). Subsequent modification and spray drying steps are exactly the same as in Example 1 to obtain an activated composite flame retardant. S2. Matrix resin blending: exactly the same as in Example 1; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, high flame-retardant elastomer composite material particles are obtained, denoted as S5.

[0052] A high flame-retardant flexible special cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a high flame-retardant flexible special cable, denoted as C5.

[0053] Example 6 A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of composite flame retardant (core-shell mass ratio 1:5, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0054] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0055] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: Nano-sized zinc hydroxystannate and magnesium hydroxide are dispersed in deionized water at a mass ratio of 1:5. Magnesium hydroxide is coated on the surface of zinc hydroxystannate by chemical deposition to obtain core-shell structured nano-zinc hydroxystannate-magnesium hydroxide composite flame retardant powder (D50=1.2μm, D97=2.8μm). Subsequent modification and spray drying steps are exactly the same as in Example 1 to obtain an activated composite flame retardant. S2. Matrix resin blending: exactly the same as in Example 1; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, high flame-retardant elastomer composite material particles are obtained, denoted as S6.

[0056] A high flame-retardant flexible special cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a high flame-retardant flexible special cable, denoted as C6.

[0057] Example 7 A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0058] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:0.5, with an addition amount of 3% of the flame retardant mass) and calcium stearate (with an addition amount of 1.5% of the flame retardant mass).

[0059] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: The preparation of core-shell structure composite flame retardant powder is exactly the same as in Example 1; the powder is formulated into an aqueous suspension with a solid content of 15%, and a composite silane coupling agent composed of A171 and KH550 in a mass ratio of 1:0.5 is added. The subsequent pH adjustment, reaction, and spray drying steps are exactly the same as in Example 1 to obtain an activated composite flame retardant. S2. Matrix resin blending: exactly the same as in Example 1; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, high flame retardant elastomer composite material particles are obtained, denoted as S7.

[0060] A high flame-retardant flexible special cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a high flame-retardant flexible special cable, denoted as C7.

[0061] Example 8 A high flame-retardant elastomer composite material, with the following components by weight: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0062] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1.5, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0063] The preparation method of the above-mentioned high flame-retardant elastomer composite material includes the following steps: S1. Pretreatment of composite flame retardant: The preparation of core-shell structure composite flame retardant powder is exactly the same as in Example 1; the powder is formulated into an aqueous suspension with a solid content of 15%, and a composite silane coupling agent composed of A171 and KH550 in a mass ratio of 1:1.5 is added. The subsequent pH adjustment, reaction and spray drying steps are exactly the same as in Example 1 to obtain the activated composite flame retardant. S2. Matrix resin blending: exactly the same as in Example 1; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, high flame-retardant elastomer composite material particles are obtained, denoted as S8.

[0064] A high flame-retardant flexible special cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a high flame-retardant flexible special cable, denoted as C8.

[0065] Comparative Example 1 An elastomeric composite material, by weight, has the following components: 100 parts of matrix resin (pure TPU, without EVA), 100 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0066] The surface of the composite flame retardant is subjected to a dual wet modification treatment with a composite silane coupling agent (A171:KH550=1:1, added at 3% of the flame retardant mass) and calcium stearate (added at 1.5% of the flame retardant mass).

[0067] The preparation method of the above-mentioned elastomeric composite material includes the following steps: S1. Pretreatment of composite flame retardant: exactly the same as in Example 1; S2. Preparation of matrix resin: Take 100 parts of TPU, without blending with EVA, and use it directly as the matrix resin; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, elastomeric composite material particles are obtained, denoted as D1.

[0068] A flexible cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a flexible cable denoted as CD1.

[0069] Comparative Example 2 An elastomeric composite material, by weight, has the following components: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of flame retardant (commercially available unmodified magnesium hydroxide, particle size 1.5μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0070] The preparation method of the above-mentioned elastomeric composite material includes the following steps: S1. Flame retardant preparation: Commercially available magnesium hydroxide (particle size 1.5μm) without surface modification can be used directly without pretreatment modification; S2. Matrix resin blending: exactly the same as in Example 1; S3. Mixing and granulation: exactly the same as in Example 1, the matrix blend, the above-mentioned unmodified magnesium hydroxide and other additives are added to a twin-screw extruder for mixing, and after extrusion, cooling and pelletizing, elastomeric composite particles are obtained, denoted as D2.

[0071] A flexible cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a flexible cable denoted as CD2.

[0072] Comparative Example 3 An elastomeric composite material, by weight, has the following components: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of composite flame retardant (core-shell mass ratio 1:3, D50=1.2μm, D97=2.8μm), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0073] The surface of the composite flame retardant was only modified by a composite silane coupling agent (A171:KH550=1:1, the amount added is 3% of the flame retardant mass), without the addition of calcium stearate.

[0074] The preparation method of the above-mentioned elastomeric composite material includes the following steps: S1. Pretreatment of composite flame retardant: The core-shell structured nano-hydroxystannate zinc-magnesium hydroxide composite flame retardant powder (preparation method is exactly the same as in Example 1, D50=1.2μm, D97=2.8μm) is prepared into an aqueous suspension with a solid content of 15%. A composite silane coupling agent composed of A171 and KH550 in a mass ratio of 1:1 is added. The mixture is reacted at 70°C for 45 minutes. No calcium stearate is added and no pH adjustment is required. The modified flame retardant is obtained directly by spray drying. S2. Matrix resin blending: exactly the same as in Example 1; S3. Mixing and granulation: exactly the same as in Example 1, through extrusion, cooling and pelletizing, elastomeric composite material particles are obtained, denoted as D3.

[0075] A flexible cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a flexible cable denoted as CD3.

[0076] Comparative Example 4 An elastomeric composite material, by weight, has the following components: 100 parts of matrix resin (70 parts of TPU, 30 parts of EVA, TPU to EVA mass ratio 1:0.4), 100 parts of flame retardant (prepared according to the method of Example 1 of CN114479183A, with zinc hydroxystannate as the core and aluminum hypophosphite as the shell, and surface coated with melamine-formaldehyde resin), 25 parts of plasticizer (TOTM), 3 parts of antioxidant (1010 and 168 compounded in a 1:1 ratio), 4 parts of crosslinking agent (DCP), 0 parts of lubricant, and 0 parts of reinforcing filler.

[0077] The preparation method of the above-mentioned elastomeric composite material includes the following steps: S1. Flame retardant preparation: Use the flame retardant prepared according to the method disclosed in CN114479183A (with zinc hydroxystannate as the core, aluminum hypophosphite as the shell, and melamine-formaldehyde resin coating on the surface), no additional modification is required; S2. Matrix resin blending: exactly the same as in Example 1; S3. Mixing and granulation: exactly the same as in Example 1, the matrix blend, the above-mentioned flame retardant and other additives are added to a twin-screw extruder for mixing, and after extrusion, cooling and pelletizing, elastomeric composite material particles are obtained, denoted as D4.

[0078] A flexible cable is prepared in the same way as in Example 1, with the sheath layer made of the above-mentioned composite material, resulting in a flexible cable denoted as CD4.

[0079] Performance testing Tensile strength and elongation at break: Tested according to GB / T 1040.3 "Determination of Tensile Properties of Plastics". The composite material particles obtained in the examples and comparative examples were dried in a 90℃ oven for 4 hours, then molded into standard dumbbell-shaped specimens with a thickness of 2.0 mm using an injection molding machine. After crosslinking by irradiation with a 5MeV electron accelerator (absorbed dose 120 kGy), tensile tests were performed on a universal testing machine at a tensile rate of 200 mm / min and an ambient temperature of 23±2℃. Five specimens were tested in each group, and the average value of the test results was taken.

[0080] Shore A hardness: Tested according to GB / T 2411 "Determination of indentation hardness (Shore hardness) of plastics and hard rubber using a hardness tester". The sample thickness is ≥6mm. After being placed in an environment of 23±2℃ for 24 hours, the Shore A hardness is measured with a Shore A hardness tester, and the average value of the test results at 5 different locations is taken.

[0081] Limiting Oxygen Index (LOI): Tested according to GB / T 2406 "Determination of Combustion Behavior by Oxygen Index Method for Plastics". The sample size is 80mm × 10mm × 3.0mm, and the minimum oxygen concentration required to sustain combustion is determined in an oxygen index meter.

[0082] UL 1581 VW-1 Vertical Burning Test: Conducted according to the VW-1 vertical burning test method in UL 1581 "Reference Standard for Wires and Cables". The cable sample is vertically fixed in a combustion chamber, and a standard flame is applied five times, each time for 15 seconds, with a 15-second interval. Judgment criteria: After five applications of flame, the sample's burning time does not exceed 60 seconds, the cotton below is not ignited by dripping material, and the burned area of ​​the paper flag above does not exceed 25%.

[0083] IEC 60332-3-22 FT4 Bundled Combustion Test: Conducted according to IEC 60332-3-22 "Vertical Flame Spread Test for Bundled Wires or Cables". The cable sample is loaded onto a standard ladder rack with 7 liters of fuel per meter, and a 20kW flame source is applied for 40 minutes. The flame spread height and self-extinguishing time are then tested.

[0084] Low-temperature embrittlement temperature: The test was conducted according to GB / T 5470 "Determination of impact embrittlement temperature of plastics". After the sample was kept at a constant temperature of -40℃ for 30 minutes, it was impacted with an impact hammer at a speed of 2m / s. Ten samples were tested at each temperature point, and the number of cracks was recorded.

[0085] Low-temperature winding test: The test shall be conducted in accordance with GB / T 2951.14 "General test methods for insulation and sheath materials of cables and optical fibers - Part 14: General test methods - Low temperature test". After placing the cable sample in a -40℃ low-temperature chamber for 4 hours, immediately wind it at a constant speed for 5 turns on a winding spool with a diameter of 6 times the outer diameter of the cable, and visually inspect the sheath layer for cracks.

[0086] Hot air aging test: The test was conducted according to GB / T 2951.12 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 12: General Test Methods - Hot Aging Test". Dumbbell-shaped test pieces were suspended in a forced-air drying oven at 150±2℃ for 168 hours. After removal, they were placed at 23±2℃ for 24 hours. The tensile strength and elongation at break after aging were tested, and the retention rate was calculated. Tensile strength retention rate (%) = (Tensile strength after aging / Tensile strength before aging) × 100% Elongation at break retention rate (%) = (Elongation at break after aging / Elongation at break before aging) × 100% High-temperature pressure test: Conducted according to GB / T 2951.31 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 31: General Test Methods - High-Temperature Pressure Test". Place the cable sample at 150°C for 4 hours while applying the specified pressure, and measure the percentage of indentation depth to sample thickness.

[0087] Temperature cycling test: Place the cable sample in a high and low temperature alternating test chamber and cycle according to the following procedure: heat to 150℃ at a rate of 5℃ / min and hold for 30 minutes; then cool to -40℃ at a rate of 5℃ / min and hold for 30 minutes; this constitutes one cycle. After 500 and 1000 cycles respectively, visually inspect the sheath layer for cracks and test the volume resistivity retention rate.

[0088] Volume resistivity: Tested according to GB / T 1410 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials". The sample was placed in an environment of 23±2℃ and 50±5% humidity for 24 hours, and the volume resistivity was measured using a high resistance meter at a DC voltage of 500V. The volume resistivity was then calculated.

[0089] The composite materials (S1-S8) prepared in Examples 1-8, the composite materials (D1-D4) prepared in Comparative Examples 1-4, and the corresponding cables (C1-C4, CD1-CD4) were subjected to performance tests. The test items and results are shown in the table below: Table 1 Mechanical and flame-retardant properties of composite materials in each embodiment and comparative example Table 2 Thermal aging and electrical performance of cables in various embodiments and comparative examples Table 3. High and low temperature cycling test results of cables in various embodiments According to the data in the table above: 1. The products of Examples 1-8 of this invention, with a low filler content of only 80-120 parts of composite flame retardant, have passed the highest level flame retardant tests of VW-1 and FT4, with an elongation at break of ≥350%, no cracking at -40℃ low temperature embrittlement, ≥80% retention rate of thermal aging performance at 150℃, and no cracking after 1000 cycles from -40℃ to 150℃. They have excellent comprehensive performance and meet the requirements of high-end special cables for new energy vehicles, energy storage systems, etc. 2. Compared with the pure TPU matrix of Comparative Example 1, the present invention significantly improves the dispersibility and interfacial compatibility of flame retardants by introducing EVA, and significantly enhances the mechanical properties, low-temperature performance and flame retardant performance of the material; 3. Compared with the unmodified flame retardant in Comparative Example 2 and the single silane modification in Comparative Example 3, the dual modification process of silane coupling agent and calcium stearate used in this invention has a significant synergistic effect, effectively improving the dispersibility and interfacial bonding of the flame retardant, and solving the industry problem of decreased mechanical properties under high filling conditions. 4. Compared with the existing flame retardant in Comparative Example 4, the composite flame retardant of the present invention has better compatibility with the TPU / EVA matrix, does not produce stress concentration, and can simultaneously ensure high flame retardancy and high flexibility, overcoming the defect that the existing technology cannot be applied to flexible elastomer systems.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high flame-retardant elastomer composite material, characterized in that, By weight, it includes the following components: 100 parts of base resin, 60-120 parts of composite flame retardant, 15-40 parts of plasticizer, 1-5 parts of antioxidant and 2-8 parts of crosslinking agent; The matrix resin is a blend of polyether thermoplastic polyurethane and ethylene-vinyl acetate copolymer, wherein the mass ratio of polyether thermoplastic polyurethane to ethylene-vinyl acetate is 1:(0.3-0.8). The composite flame retardant is an inorganic composite flame retardant with a core-shell structure. Its core is nano-zinc hydroxystannate, and its shell is magnesium hydroxide coated by chemical deposition. The surface of the composite flame retardant is subjected to dual wet modification treatment with composite silane coupling agent and calcium stearate.

2. The high flame-retardant elastomer composite material according to claim 1, characterized in that, The polyether-type thermoplastic polyurethane is a polytetrahydrofuran ether diol-type thermoplastic polyurethane with a hardness of 80A-95A; the vinyl acetate content in the ethylene-vinyl acetate is 28%-40%.

3. The high flame-retardant elastomer composite material according to claim 1, characterized in that, The composite flame retardant has a particle size of D50≤1.5μm and D97≤3.0μm; in the core-shell structure, the mass ratio of the core nano-zinc hydroxystannate to the shell magnesium hydroxide is 1:(2-5).

4. The high flame-retardant elastomer composite material according to claim 1, characterized in that, The composite silane coupling agent is a mixture of vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 1:(0.5-1.5); and the surface of the composite flame retardant is synergistically modified by the composite silane coupling agent and calcium stearate.

5. The high flame-retardant elastomer composite material according to claim 1, characterized in that, The plasticizer is at least one of trioctyl trimellitate or adipate; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1; the crosslinking agent is at least one of dicumyl peroxide or triallyl isocyanurate.

6. The high flame-retardant elastomer composite material according to claim 1, characterized in that, The composite material further includes 0-10 parts of lubricant and 0-20 parts of reinforcing filler; the lubricant is at least one of stearic acid, calcium stearate or paraffin; the reinforcing filler is surface-modified nano-calcium carbonate or fumed silica.

7. A method for preparing a high flame-retardant elastomer composite material according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Pretreatment of composite flame retardant: The core-shell structured nano-hydroxystannate zinc-magnesium hydroxide inorganic composite flame retardant powder is prepared into an aqueous suspension with a solid content of 10%-20%. A composite silane coupling agent composed of vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 1:(0.5-1.5) is added, and the mixture is reacted at 60-80℃ for 30-60 minutes. Then, the pH is adjusted to 8.0-9.0, calcium stearate is added, and the reaction is continued for 20-40 minutes. After spray drying, the activated composite flame retardant is obtained. S2. Matrix resin blending: Polyether-type thermoplastic polyurethane and ethylene-vinyl acetate copolymer are melt-blended in an internal mixer at 110-130°C in a certain proportion to obtain a matrix blend; S3. Mixing and granulation: The matrix blend obtained in step S2, the modified composite flame retardant, plasticizer, antioxidant and crosslinking agent obtained in step S1 are added to a twin-screw extruder for mixing in proportion. The screw speed is controlled at 300-600 rpm and the processing temperature is 140-170℃. After extrusion, cooling and pelletizing, high flame retardant elastomer composite material particles are obtained.

8. The method for preparing the high flame-retardant elastomer composite material according to claim 7, characterized in that, In step S3, the twin-screw extruder uses a meshing co-directional twin screw with a length-to-diameter ratio of (40-48):1 and is equipped with a side feed port. The modified composite flame retardant is added through the side feed port.

9. A highly flame-retardant flexible special cable, comprising a conductor and an insulation layer and / or sheath layer covering the outside of the conductor, characterized in that, The insulation layer and / or sheath layer are made from the high flame-retardant elastomer composite material of any one of claims 1-6 by extrusion molding and processing using irradiation crosslinking or silane crosslinking processes.

10. The high flame-retardant flexible special cable according to claim 9, characterized in that, The cable is used in high-voltage wiring harnesses in new energy vehicles or as a battery connection cable in energy storage systems.

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