Polyolefin cable material for energy storage cable and preparation method thereof

Abstract

The invention discloses a polyolefin cable material for an energy storage cable and a preparation method thereof, and relates to the technical field of cable materials, the polyolefin cable material comprises the following preparation raw materials by mass: 30-55 parts of matrix resin, 40-70 parts of a flame retardant, 2-10 parts of a compatible flexibilizer, 1-8 parts of a smoke suppressant and 1.0-5.0 parts of a processing aid; the flame retardant comprises coated aluminum hypophosphite and ceramic powder; the ceramic powder is mullite powder treated by amino silicon oil, and the coated aluminum hypophosphite is aluminum hypophosphite coated by ammonium polyphosphate and melamine-formaldehyde resin. The preparation method comprises the following steps: S1, preparing the raw materials according to the required ratio, premixing the matrix resin, and thermally mixing the other preparation raw materials to obtain a premix; and S2, carrying out melt blending, extrusion, cooling and grain-sized dicing on the premix to obtain the polyolefin cable material for the energy storage cable. The polyolefin cable material for the energy storage cable has the advantages of being high in toughness and free of molten drops on the basis of being high in flame retardance and low in fuming property.

Description

Technical Field

[0001] This invention belongs to the field of cable material technology, specifically to polyolefin cable material for energy storage cables and its preparation method. Background Technology

[0002] The energy storage compartment contains concentrated battery clusters with extremely high energy density and dense cabling. If a fire breaks out due to overheating, short circuits, or arcing, the dense smoke and toxic gases released from burning traditional cables will severely hinder personnel evacuation and firefighting efforts, potentially leading to a catastrophic chain reaction. Therefore, the cables used inside the compartment must possess extremely high flame retardancy, extremely low smoke density, absolutely no dripping, and excellent thermal stability.

[0003] Low-smoke, halogen-free flame-retardant polyolefin materials are the preferred choice for meeting the above requirements. Current technologies mainly rely on filling polyolefin matrices (such as EVA and PE) with a high proportion of metal hydroxides, such as aluminum hydroxide (ATH) or magnesium hydroxide. These fillers exert their flame-retardant effect by decomposing and absorbing heat and releasing water vapor. However, this system has inherent drawbacks: First, to achieve the UL94V-0 rating, the extremely high filler content severely degrades the mechanical properties of the material, resulting in poor flexibility, low elongation, and brittleness; second, the high filler content leads to a sharp increase in melt viscosity, making processing and extrusion difficult and resulting in a rough cable surface; finally, the flame-retardant efficiency of hydroxides is limited, and the char layer formed during combustion is loose and porous, with poor suppression of smoke and heat, making it difficult to meet the extreme safety requirements of energy storage scenarios.

[0004] To address these issues, the industry has attempted various methods, such as compounding hydroxides with different particle sizes, using silane coupling agents for surface treatment, or introducing intumescent flame retardants (e.g., ammonium polyphosphate, APP). However, these solutions often have trade-offs: ammonium polyphosphate has poor compatibility with polyolefins, is hygroscopic, and easily decomposes at processing temperatures, leading to decreased material thermal stability and surface degradation; simple surface treatments have limited effectiveness in improving processing flowability under extremely high filler conditions; and systematic synergistic research on smoke suppression and anti-dripping is still insufficient. Patent document CN109627568A discloses a polyolefin cable sheath material and its preparation method, which uses microencapsulated aluminum hypophosphite as a flame retardant. The flame retardant formed by a single coating agent only solves the oxidation and corrosion problems of aluminum hypophosphite, and requires the simultaneous compounding of three different microcapsules to achieve a certain flame retardant effect. Summary of the Invention

[0005] To overcome the aforementioned technical problems, this invention provides a polyolefin cable material for energy storage cables and its preparation method. The polyolefin cable material for energy storage cables of this invention possesses advantages such as high flame retardancy, low smoke emission, high toughness, and no dripping properties.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] This invention discloses a polyolefin cable material for energy storage cables, comprising the following raw materials in parts by weight: 30-55 parts matrix resin, 40-70 parts flame retardant, 2-10 parts compatibility toughening agent, 1-8 parts smoke suppressant, and 1.0-5.0 parts processing aids; Preferably, the polyolefin cable material for energy storage cables comprises the following raw materials in parts by weight: 35-50 parts matrix resin, 50-65 parts flame retardant, 3-8 parts compatibility toughening agent, 2-6 parts smoke suppressant, and 1.5-4.0 parts processing aids; The matrix resin, by mass fraction, comprises 15-50% polyolefin elastomer and the balance polyethylene resin; preferably, the matrix resin comprises 20-40% polyolefin elastomer and the balance polyethylene resin. The flame retardant includes coated aluminum hypophosphite and ceramic powder; the coated aluminum hypophosphite is aluminum hypophosphite coated with ammonium polyphosphate and melamine-formaldehyde resin; wherein, in the early stage of combustion, ammonium polyphosphate decomposes to generate phosphoric acid compounds, which catalyze the dehydration and crosslinking of the polymer matrix to form an expanded carbon layer, while capturing free radicals in the gas phase; the hydrophobicity of melamine-formaldehyde resin can reduce moisture absorption; The ceramic powder is mullite powder treated with amino silicone oil; mullite powder itself is more hydrophilic, and the mullite powder treated with amino silicone oil has better compatibility with the matrix resin; in addition, the porous structure on the surface of mullite provides adsorption and catalytic sites, transforming the traditional gas-solid phase flame retardant into a condensed phase charring flame retardant mode.

[0008] According to some embodiments of the present invention, the flame retardant, by mass fraction, comprises 5-25 wt% coated aluminum hypophosphite, 3-20 wt% ceramic powder, 0.5-2.5% silicone powder, and the balance magnesium hydroxide; Preferably, the flame retardant is composed of 10-20 wt% coated aluminum hypophosphite, 5-15 wt% ceramic powder, 0.8-1.5% silicone powder, and the balance magnesium hydroxide; According to some embodiments of the present invention, the polyethylene resin is at least one selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and ethylene-vinyl acetate copolymer (EVA). The preferred materials are low-density polyethylene (LDPE) or ethylene-vinyl acetate copolymer (EVA, VA content 18%~28%).

[0009] According to some embodiments of the present invention, the polyolefin elastomer is at least one selected from ethylene-octene copolymer (POE), ethylene-butene copolymer (PBE), styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), and ethylene propylene diene monomer (EPDM); preferably, it is ethylene-octene copolymer (POE).

[0010] According to some embodiments of the present invention, the D50 of the mullite powder is 30~60μm, preferably 40~50μm.

[0011] According to some embodiments of the present invention, the refractoriness of the mullite powder is ≥1780℃, preferably 1790~1800℃.

[0012] According to some embodiments of the present invention, the mullite powder comprises, by mass fraction: 51~54% SiO2, 44~46% Al2O3, Fe2O3≤0.8%, TiO2≤1.4%, and CaO+MgO≤0.3%.

[0013] According to some embodiments of the present invention, the D50 of the magnesium hydroxide is 3~10 μm.

[0014] According to some embodiments of the present invention, the D50 of the aluminum hypophosphite is 10~40 μm.

[0015] According to some embodiments of the present invention, the compatibility toughening agent is a maleic anhydride grafted polymer, preferably a maleic anhydride grafted polyolefin elastomer (POE-g-MAH), a maleic anhydride grafted polyethylene (PE-g-MAH), or a maleic anhydride grafted ethylene-vinyl acetate ester (EVA-g-MAH).

[0016] According to some embodiments of the present invention, the smoke suppressant comprises 15-45% ferrocene and the balance zinc borate; preferably, the smoke suppressant comprises 20-40% ferrocene and the balance zinc borate. Ferrocene can capture gaseous free radicals, while zinc borate can act as a condensed phase ceramic anti-dripping agent.

[0017] According to some embodiments of the present invention, the processing aid is at least one of a lubricant, an antioxidant, and a dispersant.

[0018] Furthermore, the lubricant is one or more of zinc stearate, calcium stearate, polyethylene wax, and oxidized polyethylene wax, with zinc stearate being preferred.

[0019] Further, the antioxidant is at least one of antioxidant 1076, antioxidant 1010, and dilauryl thiodipropionate (DLTP), with antioxidant 1076 being preferred.

[0020] Furthermore, the dispersant is one of ethylene bis-stearamide (EBS), N,N'-ethyl bis-stearamide, or silicone powder.

[0021] According to some embodiments of the present invention, the limiting oxygen index (LOI) of the polyolefin cable material for energy storage cables is 39-42%; According to some embodiments of the present invention, the smoke density (Ds) of the polyolefin cable material for energy storage cables is 80~100; According to some embodiments of the present invention, the tensile strength of the polyolefin cable material for the energy storage cable is ≥12MPa; According to some embodiments of the present invention, the elongation at break of the polyolefin cable material for the energy storage cable is ≥180%.

[0022] This invention also discloses a method for preparing low-smoke halogen-free flame-retardant polyolefin cable material for energy storage cables, comprising the following steps: S1. Prepare raw materials according to the required ratio, premix the matrix resin, and then heat mix the other raw materials to obtain the premix; S2. The premixed material is melt-blended, extruded, cooled, and pelletized to obtain polyolefin cable material for energy storage cables.

[0023] S1 also includes the steps of pre-preparing key components, namely the preparation of coated aluminum hypophosphite, the preparation of ceramic powder and the preparation of flame retardant; In S1, the preparation of the coated aluminum hypophosphite is as follows: 100 parts of aluminum hypophosphite are added to water to prepare a suspension with a solid content of 20-40%, and the pH is adjusted to 7.5-8.5; the suspension is heated to 65-75℃ and 5-15 parts of ammonium polyphosphate are added and stirred for 60-120 min, then 3-10 parts of melamine and 2.4-12 parts of formaldehyde solution (37%) are slowly added, the pH is adjusted to 4.5-5.5 and stirring is continued for 120-180 min. After the reaction is completed, coated aluminum hypophosphite is obtained.

[0024] In S1, the preparation of the ceramic powder is as follows: Mullite powder is placed in a high-speed mixer and preheated to 70~90℃. At a speed of 500~800 rpm, amino silicone oil accounting for 1.0~3.0% of the mass of mullite is slowly added by atomization spraying. After spraying, the mixture is kept warm and stirred for 20~40 minutes. The mixture is then discharged and cooled.

[0025] In S1, the flame retardant is prepared by mixing coated aluminum hypophosphite, ceramic powder and magnesium hydroxide, and then slowly adding silicone powder at 50~70°C, and mixing at 500~800 rpm for 10~20 min to obtain the flame retardant. In S1, the premix is ​​stirred at 45~65℃ for 5~15 min; In S1, the thermal mixing is carried out at 65~85°C and at a speed of 600~900 rpm for 10~20 minutes. In S2, the melt blending is performed using a twin-screw extruder; the temperatures of each section of the twin-screw extruder are set as follows: feeding section 140~160℃, melting section 150~170℃, first mixing section 165~180℃, second mixing section 170~185℃, venting section 165~175℃, and die head 165~175℃; the twin-screw speed is 250~400rpm, and the vacuum degree is controlled at -0.06~-0.08MPa.

[0026] In S2, the cooling method is water cooling at 25~45℃.

[0027] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0028] Compared with the prior art, the beneficial effects of the present invention are: 1. The matrix resins selected in this invention are polyethylene resin and polyolefin elastomer, respectively. This combination can, to some extent, mitigate the performance degradation caused by high filler content. Polyolefin elastomers provide flexibility and impact resistance.

[0029] 2. Coating with aluminum hypophosphite effectively isolates it from direct contact with the matrix resin, completely preventing the catalytic degradation of polymer molecular chains by acidic substances during high-temperature melting and processing, thus ensuring melt viscosity and stability. Compared to traditional physical coatings and single-function coating agents, this invention uses a dual-function coating agent of ammonium polyphosphate and melamine-formaldehyde resin, sequentially coating aluminum hypophosphite using an aqueous solution chemical coating method. After coating, in the initial stage of combustion, the polyphosphate catalyzes the dehydration of the matrix to form char, creating an expanded char layer. The nitrogen gas generated from the decomposition of melamine-formaldehyde resin further promotes the expansion of the char layer. This solves the high flame retardancy and high stability requirements of energy storage scenarios that traditional aluminum hypophosphite cannot meet.

[0030] 3. The composite flame-retardant system of this invention consists of magnesium hydroxide, ceramic powder (mainly mullite), and coated aluminum hypophosphite. The components work synergistically to achieve high efficiency, low smoke, and drip-free flame-retardant performance. Magnesium hydroxide, as an environmentally friendly inorganic flame retardant, cools the material surface through endothermic decomposition (approximately 340°C), releasing water vapor to dilute combustible gases and oxygen concentrations, and forming a stable oxide coating layer on the material surface. The mullite ceramic powder has a porous structure, which can adsorb smoke particles and volatile hydrocarbon products released during combustion, while simultaneously constructing a dense barrier layer on the surface to inhibit heat and mass transfer. Coated aluminum hypophosphite decomposes at high temperatures to generate phosphorus-nitrogen-based flame-retardant active substances, promoting char layer formation and enhancing its density; it works synergistically with the smoke suppressant ferrocene in the system. Ferrocene, as a free radical scavenger, effectively inhibits the combustion chain reaction and reduces the release of smoke and toxic gases.

[0031] 4. The cable material of this invention possesses high flame retardancy, low smoke emission, high toughness, and no dripping properties. It is expected to be used in energy storage cables to ensure the safety of energy storage facilities. Detailed Implementation

[0032] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0034] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is understood that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0038] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0039] Unless otherwise specified, the term "or" is inclusive in this invention. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0040] The raw material information used in the following examples is as follows: Ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content of 18% and a tensile breaking strength of 19 MPa; The ethylene-octene copolymer (POE) is manufactured by Dow, and its melt flow rate (190℃, 2.16kg) is 5.0g / 10min, elongation at break is 550%, and tensile strength is 2.4MPa. The D50 of aluminum hypophosphite is 15 μm; Mullite powder was purchased from Xinyan calcined kaolin (325 mesh) in Yidu City, with a refractoriness ≥1790℃ and a mullite phase content of 55-60%. The amino silicone oil is Corning 8040A; Maleic anhydride-grafted polyolefin elastomer (POE-g-MAH) was purchased from Jiayirong Polymer (Shanghai) Co., Ltd. FB521A; This includes, but is not limited to, the models from the above manufacturers.

[0041] Example 1 1. The raw materials for preparing the polyolefin cable material for energy storage cables in this embodiment are as follows: 42.0 parts matrix resin, 58 parts flame retardant, 5.5 parts compatibility toughening agent, 4.0 parts smoke suppressant and 2.8 parts processing aid; The matrix resin in this embodiment is 29.4 parts EVA and 12.6 parts POE; The flame retardant in this embodiment consists of 15 wt% coated aluminum hypophosphite, 10 wt% ceramic powder, 1.2 wt% silicone powder, and the balance magnesium hydroxide. The compatibility toughening agent in this embodiment is POE-g-MAH; The coated aluminum hypophosphite is aluminum hypophosphite coated with ammonium polyphosphate and melamine-formaldehyde resin; The ceramic powder is mullite powder treated with amino silicone oil; In this embodiment, the processing aids are 1.7 parts zinc stearate, 0.5 parts antioxidant 1076, and 0.6 parts EBS; In this embodiment, the smoke suppressant is 30wt% ferrocene and the balance zinc borate.

[0042] 2. The preparation method of the polyolefin cable material for energy storage cables in this embodiment is as follows: S1.1. Prefabrication of key components Preparation of ceramic powder: Place mullite powder in a high-speed mixer and preheat to 80°C. At a speed of 600 rpm, slowly add amino silicone oil accounting for 2.0% of the mass of mullite by atomization spray. After spraying, continue to keep warm and stir at 80°C for 30 minutes. Discharge and cool. Preparation of coated aluminum hypophosphite: 100 parts of aluminum hypophosphite (D50=10μm) were added to water to prepare a suspension with a solid content of 30%. The pH was adjusted to 8.0 with ammonia. The suspension was heated to 70℃ and 10 parts of ammonium polyphosphate were added and stirred for 90 min. Then, 6 parts of melamine and 7.5 parts of 37% formaldehyde solution were slowly added. The pH was adjusted to 5.0 with 10% acetic acid solution and stirring was continued for 150 min. After the reaction was completed, coated aluminum hypophosphite was obtained.

[0043] Preparation of flame retardant: According to the above formula requirements, magnesium hydroxide, coated aluminum hypophosphite and ceramic powder are mixed in a high-speed mixer; then silicone powder is slowly added at 60°C and processed at 600 rpm for 12 minutes, and then discharged for later use. S1.2 Mixing The matrix resin was put into a high-speed mixer and stirred at 400 rpm for 10 minutes at 55°C to obtain a premixed resin. The remaining raw materials were added to the premixed resin and hot-mixed at 700 rpm and 75°C for 15 min to obtain the premix.

[0044] S2. Feed the premixed material into a twin-screw extruder; Temperature settings for each section of the screw: feeding section 150°C, melting section 160°C, first mixing section 175°C, second mixing section 180°C, exhaust section 170°C, and die head 170°C; The screw speed is 320 rpm, and the vacuum degree is controlled at -0.07 MPa; the melt-extruded strip is cooled in a 35°C water bath; the cooled strip is cut into pellets to obtain cylindrical particles with a particle size of 3.0 mm.

[0045] Example 2 The difference between this embodiment and Embodiment 1 is as follows: 47.6 parts matrix resin, 52 parts flame retardant, 6.7 parts compatibility toughening agent, 5.0 parts smoke suppressant and 2.8 parts processing aid; The matrix resin in this embodiment is 13.5 parts EVA and 34.1 parts POE; The other raw materials, steps and parameters are the same as in Example 1.

[0046] Example 3 The difference between this embodiment and Embodiment 1 is as follows: The flame retardant in this embodiment consists of 15 wt% coated aluminum hypophosphite, 5 wt% ceramic powder, 1.2 wt% silicone powder, and the balance magnesium hydroxide. The other raw materials, steps and parameters are the same as in Example 1.

[0047] Example 4 The difference between this embodiment and Embodiment 1 is as follows: The flame retardant in this embodiment consists of 20 wt% coated aluminum hypophosphite, 5 wt% ceramic powder, 1.2 wt% silicone powder, and the balance magnesium hydroxide. The other raw materials, steps and parameters are the same as in Example 1.

[0048] Example 5 The difference between this embodiment and Embodiment 1 is as follows: The ceramic powder in this embodiment is mullite powder, which has not been treated with amino silicone oil. The other raw materials, steps and parameters are the same as in Example 1.

[0049] In this embodiment, the ceramic powder has poor compatibility with the matrix resin, uneven dispersion, significantly reduced smoke suppression, and a simultaneous decrease in mechanical properties.

[0050] Example 6 The difference between this embodiment and Embodiment 1 is as follows: The smoke suppressant in this embodiment is only ferrocene; The other raw materials, steps and parameters are the same as in Example 1.

[0051] Example 7 The difference between this embodiment and Embodiment 1 is as follows: The smoke suppressant in this embodiment is only zinc borate; The other raw materials, steps and parameters are the same as in Example 1.

[0052] Zinc borate has a good effect on inhibiting dripping when carbonized, but it lacks the ability to capture gas-phase free radicals and has insufficient smoke suppression performance.

[0053] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: The flame retardant used in this comparative example is aluminum hypophosphite, which has not undergone any coating treatment. The other raw materials, steps and parameters are the same as in Example 1.

[0054] The acidic aluminum hypophosphite in this comparative example degrades the matrix resin during processing, leading to a decrease in molecular weight. Although the flame retardancy is still acceptable, the material loses its usability.

[0055] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: The flame retardant in this comparative example does not contain ceramic powder. The flame retardant consists of 20 wt% coated aluminum hypophosphite, 1.2 wt% silicone powder, and the balance magnesium hydroxide. The other raw materials, steps and parameters are the same as in Example 1.

[0056] This comparative example does not contain ceramic powder, resulting in low flame retardant efficiency and poor smoke and drip suppression capabilities.

[0057] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: The flame retardant in this comparative example consists of 15 wt% ceramic powder, 1.2 wt% silicone powder, and the balance magnesium hydroxide; the flame retardant does not contain coated aluminum hypophosphite. The other raw materials, steps and parameters are the same as in Example 1.

[0058] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: The flame retardant in this comparative example consists of 15 wt% coated aluminum hypophosphite, 10 wt% talc, 1.2 wt% silicone powder, and the balance magnesium hydroxide; the flame retardant used in this comparative example is talc instead of mullite powder treated with amino silicone oil. The other raw materials, steps and parameters are the same as in Example 1.

[0059] In this comparative example, the talc powder only serves as a physical filler, and due to its lack of a porous surface structure, it is difficult to replace ceramic powder.

[0060] Test case The polyolefin cable material for energy storage cables prepared in the above embodiments and comparative examples was subjected to the following tests, and the test results are shown in Table 1. Limiting Oxygen Index (LOI) Test: GB / T 2406.2-2009; Smoke density (Ds) test: GB / T 8323.2-2008, using a cone calorimeter, 50kW / m³ 2 Maximum specific optical density under radiation intensity; Tensile strength and elongation at break: GB / T 1040.2-2006; Melting drop test: GB / T 2408-2021, observe whether the degreased cotton is ignited and the melting drop situation in the vertical burning test.

[0061]

[0062] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this invention. It should be understood that the above descriptions are merely specific embodiments of this invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A polyolefin cable material for energy storage cables, characterized in that, The preparation raw materials include the following parts by weight: 30-55 parts matrix resin, 40-70 parts flame retardant, 2-10 parts compatibility toughening agent, 1-8 parts smoke suppressant and 1.0-5.0 parts processing aid; By mass fraction, the matrix resin is 15-50% polyolefin elastomer and the balance is polyethylene resin; The flame retardant includes coated aluminum hypophosphite and ceramic powder; the coated aluminum hypophosphite is aluminum hypophosphite coated with ammonium polyphosphate and melamine-formaldehyde resin; The ceramic powder is mullite powder treated with amino silicone oil.

2. The polyolefin cable material for energy storage cables as described in claim 1, characterized in that, The flame retardant, by mass fraction, comprises 5-25 wt% coated aluminum hypophosphite, 3-20 wt% ceramic powder, 0.5-2.5% silicone powder, and the balance magnesium hydroxide.

3. The polyolefin cable material for energy storage cables as described in claim 2, characterized in that, The polyethylene resin is at least one of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer; And / or, the polyolefin elastomer is at least one of ethylene-octene copolymer, ethylene-butene copolymer, styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, and ethylene propylene diene monomer (EPDM) rubber.

4. The polyolefin cable material for energy storage cables as described in claim 2, characterized in that, At least one of the following conditions a to d must be met: a. The D50 of the mullite powder is 30~60μm; b. The refractoriness of the mullite powder is ≥1780℃; c. The D50 of the magnesium hydroxide is 3~10 μm; d. The D50 of the aluminum hypophosphite is 10~40 μm.

5. The polyolefin cable material for energy storage cables as described in claim 1, characterized in that, At least one of the following conditions a to c must be met: a. The compatibility toughening agent is a maleic anhydride-grafted polymer, preferably a maleic anhydride-grafted polyolefin elastomer, a maleic anhydride-grafted polyethylene, or a maleic anhydride-grafted ethylene-vinyl acetate ester. b. The smoke suppressant is 15-45% ferrocene and the balance zinc borate; c. The processing aid is at least one of lubricant, antioxidant and dispersant.

6. The polyolefin cable material for energy storage cables as described in claim 1, characterized in that, At least one of the following conditions a to d must be met: a. The limiting oxygen index of the polyolefin cable material used in the energy storage cable is 39-42%; b. The smoke density of the polyolefin cable material used in the energy storage cable is 80~100; c. The tensile strength of the polyolefin cable material used in the energy storage cable is ≥12MPa; d. The elongation at break of the polyolefin cable material for the energy storage cable is ≥180%.

7. A method for preparing low-smoke halogen-free flame-retardant polyolefin cable material for energy storage cables, characterized in that, Includes the following steps: S1. Prepare raw materials according to the required ratio, premix the matrix resin, and then heat mix the other raw materials to obtain the premix; S2. The premixed material is melt-blended, extruded, cooled, and pelletized to obtain polyolefin cable material for energy storage cables.

8. The preparation method of the low-smoke halogen-free flame-retardant polyolefin cable material for energy storage cables as described in claim 7, characterized in that, S1 also includes the steps of pre-preparing key components, namely the preparation of coated aluminum hypophosphite, the preparation of ceramic powder and the preparation of flame retardant; Preparation of the flame retardant: Aluminum hypophosphite coated with ceramic powder and magnesium hydroxide are mixed, and then silicone powder is slowly added at 50~70℃. The mixture is stirred at 500~800rpm for 10~20min to obtain the flame retardant. In S1, the premix is ​​stirred at 45~65℃ for 5~15 min; In S1, the thermal mixing is carried out at 65~85℃ and at a speed of 600~900rpm for 10~20min.

9. The preparation method of the low-smoke halogen-free flame-retardant polyolefin cable material for energy storage cables as described in claim 8, characterized in that, Preparation of coated aluminum hypophosphite: 100 parts of aluminum hypophosphite are added to water to prepare a suspension with a solid content of 20-40%, and the pH is adjusted to 7.5-8.5; the suspension is heated to 65-75℃, and 5-15 parts of ammonium polyphosphate are added and stirred for 60-120 min; then 3-10 parts of melamine and 2.4-12 parts of formaldehyde solution are slowly added, the pH is adjusted to 4.5-5.5, and stirring is continued for 120-180 min. After the reaction is completed, coated aluminum hypophosphite is obtained. And / or, the preparation of the ceramic powder: place mullite powder in a high-speed mixer, preheat to 70~90℃, and slowly add 1.0~3.0% of amino silicone oil by mass of mullite at a speed of 500~800 rpm using an atomized spray method. After spraying, continue to keep warm and stir for 20~40 minutes, and then discharge and cool.

10. The method for preparing low-smoke halogen-free flame-retardant polyolefin cable material for energy storage cables as described in claim 7, characterized in that, In S2, the melt blending is performed using a twin-screw extruder; wherein the temperatures of each section of the twin-screw extruder are set as follows: feeding section 140~160℃, melting section 150~170℃, first mixing section 165~180℃, second mixing section 170~185℃, venting section 165~175℃, and die head 165~175℃; and / or, the twin-screw speed is 250~400rpm, and the vacuum degree is controlled at -0.06~-0.08MPa; And / or, in S2, the cooling is performed using a water cooling method at 25~45℃.

Images