105 deg.c. low smoke halogen-free radiation crosslinking polyolefin insulating material and preparation method thereof

Abstract

The present application relates to the technical field of low-smoke halogen-free flame-retardant cable material, and particularly relates to a 105 DEG C low-smoke halogen-free radiation crosslinking polyolefin insulating material and a preparation method. The 105 DEG C low-smoke halogen-free radiation crosslinking polyolefin insulating material comprises a base resin composed of HDPE, LLDPE metallocene and POE, a composite flame retardant, a sensitizer, a compatibilizer, an antioxidant, a lubricant, a silane coupling agent and a dispersant. Through whole-process collaborative optimization of mixing-irradiation-post-treatment, the problems of high-filled halogen-free flame-retardant material processing difficulty, uneven crosslinking, poor thermal stability and the like are solved, and the material is suitable for high-end wire and cable insulating layer manufacturing, and has the advantages of high efficiency, environmental protection and high reliability.

Description

Technical Field

[0001] This invention relates to the field of low-smoke halogen-free flame-retardant cable materials, and in particular to a 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulation material and its preparation method. Background Technology

[0002] Irradiation-crosslinked low-smoke halogen-free polyolefin insulation is a high-performance, environmentally friendly polymer material used in the insulation layers of wires and cables. Its core components are polyolefins (such as ethylene-vinyl acetate copolymer EVA, polyethylene PE, polyolefin elastomer POE, etc.) as the matrix resin, with added halogen-free flame retardants (mainly metal hydroxides, such as aluminum hydroxide ATH, magnesium hydroxide MH), synergistic flame retardants, smoke suppressants, antioxidants, processing aids, etc., prepared into compound granules or sheets through a melt blending process. The key characteristic of this material lies in subsequent high-energy electron beam (or gamma ray) irradiation treatment, which induces the formation of a crosslinked network structure between the polyolefin molecular chains.

[0003] Irradiation crosslinking technology endows this material with significantly superior properties compared to ordinary thermoplastic polyolefins, including: excellent heat resistance, as the crosslinked network greatly improves the material's heat distortion temperature, significantly enhancing dimensional stability and long-term reliability at high temperatures; outstanding mechanical properties, significantly improving tensile strength, abrasion resistance, compressive strength, and environmental stress cracking resistance (ESCR) at high temperatures; good electrical properties, meeting the insulation resistance and dielectric strength requirements for wire and cable insulation; inherent low-smoke and halogen-free characteristics, containing no halogen elements such as chlorine and bromine, resulting in extremely low smoke release during combustion and minimal corrosive gases (such as hydrogen halides), complying with stringent fire safety and environmental regulations (such as RoHS, REACH, IEC 60754, IEC 61034, etc.), and is widely used in locations with extremely high requirements for personnel safety and equipment protection. Following the "Xi'an Aokai" incident, B1-grade cables are mandated for densely populated locations such as subways, airports, and hospitals. GB The 31247-2014 standard for "Classification of Combustion Performance of Cables and Optical Fibers" sets higher requirements for B1 grade cables in terms of heat release, smoke generation, drippings, and smoke toxicity.

[0004] Despite the numerous advantages of irradiated crosslinked low-smoke halogen-free polyolefin insulation materials, several pressing issues remain in practical applications and current technologies: ① Conflict between mechanical properties and flame retardancy: Traditional halogen-free flame retardants (such as aluminum hydroxide and magnesium hydroxide) require high filler content to meet flame retardant standards, but excessive filler can reduce the material's mechanical properties and processing fluidity. ② Poor stability of the irradiation process: Precise control of irradiation dosage and uniformity can easily lead to uneven crosslinking, affecting the insulation material's heat aging resistance and long-term reliability. ③ Insufficient smoke density control: While some formulations meet the halogen-free requirement during combustion, their smoke density remains high, making it difficult to meet higher fire safety standards.

[0005] In response to the aforementioned technologies, there is an urgent need in this field to develop a 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulation material and its preparation method, so as to solve the technical problems existing in the heat resistance, flexibility, processability, flame retardant efficiency, long-term aging performance and cost of the current irradiated crosslinked low-smoke halogen-free polyolefin insulation material. Summary of the Invention

[0006] To address the problems of existing irradiated crosslinked low-smoke halogen-free polyolefin insulation materials in terms of heat resistance, flexibility, processability, flame retardant efficiency, long-term aging performance, and cost, this application provides an irradiated crosslinked low-smoke halogen-free polyolefin insulation material and its preparation method.

[0007] In a first aspect, this application provides a 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulating material, employing the following technical solution: A 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulating material is prepared from the following raw materials in parts by weight: 100 parts of matrix resin, 100-130 parts of composite flame retardant, 2-4 parts of sensitizer, 3-8 parts of compatibilizer, 0.6-2 parts of antioxidant, 2.0-2.5 parts of lubricant, 0.8-1.0 parts of silane coupling agent, and 0.4-0.6 parts of dispersant; The matrix resin is HDPE, LLDPE, metallocene, and POE in a weight ratio of (4-6):(2-3):(2-3). The sensitizer is TMPTMA and silicone masterbatch in a weight ratio of (1-2.5):(1-1.5). The lubricant is paraffin wax and oxidized polyethylene wax in a weight ratio of (1-1.5):1; The silane coupling agent is coupling agent 172; The dispersant is zinc stearate.

[0008] By adopting the above scheme, the matrix resin, HDPE, provides a rigid skeleton to ensure the dimensional stability of the material at a high temperature of 105℃. LLDPE, a metallocene resin, enhances melt strength and the uniformity of irradiation crosslinking, effectively improving the surface finish of the extrusion and reducing the risk of melt fracture. POE imparts flexibility and impact resistance, preventing embrittlement after crosslinking. The balance of rigidity and flexibility among these three components results in high tensile strength and an elongation at break ≥300%, superior to traditional PVC or EVA base materials. It also avoids the delamination phenomenon of traditional HDPE and POE systems under high shear. In the sensitizer, TMPTMA accelerates the free radical crosslinking reaction, while the silicone masterbatch promotes the uniform distribution of the crosslinking network, reducing the required irradiation dose and providing both lubrication and sensitization functions, thus reducing the coefficient of friction. The compatibilizer POE-g-MAH strengthens the interfacial bonding between the flame retardant and the resin, preventing stress cracking. EMA-g-MAH improves the compatibility of polar EMA segments with the flame retardant, reducing interfacial defects. The lubricant combination helps balance internal and external lubrication. Paraffin wax provides external lubrication, forming a molecular layer at the melt-equipment interface, and it resists oxidation migration. Oxidized polyethylene wax provides internal lubrication, with long-chain alkanes penetrating the polymer chain to reduce intermolecular entanglement. Simultaneously, the carboxyl groups of oxidized polyethylene wax synergistically enhance the bonding force between the flame retardant and resin with the compatibilizer. Silane coupling agents react with the outer -OH layer of the flame retardant, improving its hygrothermal stability. Dispersants effectively prevent the flame retardant from absorbing moisture and agglomerating. Through multi-component synergistic design, this formulation significantly improves temperature resistance, mechanical strength, and processing performance while maintaining low-smoke, halogen-free, and environmentally friendly characteristics.

[0009] Preferably, the HDPE has a melt index of 1-3 g / 10 min at 190°C and 2.16 kg.

[0010] Preferably, the POE has a melt flow rate of 18 g / 10 min.

[0011] Preferably, the composite flame retardant is prepared by the following steps: pretreating nano-magnesium hydroxide with silane coupling agent KH-550, adding vinyl phosphonate monomer and APS initiator, performing a grafting reaction, adding zinc borate, mixing in a high-speed mixer, heating to melt the surface, cooling, and then pulverizing and sieving.

[0012] Preferably, the composite flame retardant is nano magnesium hydroxide, KH550, vinyl phosphonate monomer, APS initiator and zinc borate in a weight ratio of 100:(3-5):(8-12):(0.3-0.5):(10-15).

[0013] Preferably, the composite flame retardant is prepared by dissolving KH-550 in anhydrous ethanol at 8 times its mass, spraying the solution onto magnesium hydroxide powder, processing it in a high-speed mixer at 3000 rpm for 15 min, and vacuum drying it at 60°C until the moisture content is ≤0.5% to obtain pretreated magnesium hydroxide. The pretreated magnesium hydroxide, vinyl phosphonate monomer, and APS initiator are added to a reaction vessel, heated to 80°C under nitrogen protection, and stirred for 2 h. The product is washed three times with ethanol and dried at 80°C to obtain a vinyl phosphonate grafted product. The vinyl phosphonate grafted product and zinc borate are mixed in a high-speed mixer, heated to 180°C for cladding for 10 min, cooled, and then pulverized through a 400-mesh sieve.

[0014] Preferably, the composite flame retardant has a volume resistivity ≥ 3 × 10⁻⁶. 15 Ω·m (105℃), dielectric strength ≥28 kV / mm, elongation at break 380%, elongation retention ≥80%, thermal life >20000h.

[0015] By adopting the above scheme, a triple synergistic effect of flame retardancy, smoke suppression and interface strengthening is achieved. KH-550 pretreatment forms Si-O-Mg bonds, which improves hydrophobicity and enhances compatibility with resin. Vinyl phosphonate grafting decomposes POC bonds at high temperature to generate a phosphate glass layer, which isolates oxygen. Zinc borate cladding melts and covers cracks with ZnB4O7, catalyzing the formation of a dense carbon layer.

[0016] Preferably, the compatibilizer is either POE-g-MAH or EMA-g-MAH; its grafting rate is 1.2-1.6wt%; its melt index is 2-8g / 10min at 190℃ and 2.16kg; and its acid value is 8-15mg KOH / g.

[0017] By adopting the above scheme, the flame retardant-resin interface is strengthened. The large polarity difference between the composite flame retardant and the polyolefin matrix easily leads to uneven dispersion. The maleic anhydride (MAH) polar groups in POE-g-MAH or EMA-g-MAH can form hydrogen bonds or chemical bonds with the flame retardant surface, improving the interfacial bonding between the inorganic filler and the resin and reducing phase separation. The compatibilizer, through its "bridging" effect, prevents the flame retardant from agglomerating, ensuring that the material maintains uniform mechanical properties after radiation crosslinking and preventing performance degradation. Simultaneously, POE-g- The introduction of MAH or EMA-g-MAH lubricates the polymer chains, reduces the obstruction of melt flow by flame retardants, improves extrusion processability, and avoids processing difficulties caused by high-filler flame retardant levels. Synergistically with paraffin and oxidized polyethylene wax lubricants in the formulation, it further reduces processing energy consumption and improves production efficiency. The unsaturated double bonds in POE-g-MAH undergo irradiation crosslinking reactions, working with sensitizers to increase crosslinking density and form a more stable three-dimensional network structure, thereby improving temperature resistance (long-term use at 105℃) and aging resistance. By selecting POE-g-MAH or EMA-g-MAH as compatibilizers, through interface modification, processing optimization, and crosslinking promotion, the mechanical strength, temperature resistance, flame retardancy, and processing performance of the insulation material are comprehensively improved, while meeting the requirements for long-term stable use at 105℃.

[0018] Preferably, the POE-g-MAH is prepared by the following steps: adding POE, maleic anhydride, dicumyl peroxide, and styrene to a high-speed mixer and mixing at 60-80°C for 5 min; adding to a twin-screw extruder and controlling the screw temperature zones as follows: feeding zone: 80-100°C, melting zone: 160-180°C, reaction zone: 180-190°C, vacuum devolatilization zone: -0.08 MPa, screw speed: 200-400 rpm, residence time: 1.5-2.5 min; the extruded strip is water-cooled and pelletized, and then vacuum-dried at 70°C for 4 h to obtain POE-g-MA.

[0019] Preferably, in the POE-g-MAH, the weight ratio of POE, maleic anhydride, dicumyl peroxide and styrene is 100:(1.5-3.0):(0.1-0.3):(0.5-1.0).

[0020] Preferably, the EMA-g-MAH is prepared by the following steps: adding EMA, maleic anhydride, dicumyl peroxide, and styrene to a high-speed mixer and mixing at 70-85°C for 5 min; adding to a twin-screw extruder and controlling the screw temperature zones as follows: feeding zone: 85-95°C, melting zone: 160-175°C, reaction zone: 180-190°C, vacuum devolatilization zone: -0.08 MPa, screw speed: 200-400 rpm, residence time: 1.5-2.5 min; the extruded strip is water-cooled and pelletized, and then vacuum-dried at 70°C for 4 h to obtain EMA-g-MAH.

[0021] Preferably, in the EMA-g-MAH, the weight ratio of EMA, maleic anhydride, dicumyl peroxide and styrene is 100:(1.5-2.5):(0.1-0.3):(0.5-1.0).

[0022] Preferably, the antioxidant is antioxidant 1010, antioxidant 168 and DLTP in a weight ratio of (0.2-1.0):(0.2-0.6):(0.2-0.4).

[0023] By adopting the above scheme, antioxidant 1010 acts as the primary antioxidant to capture free radicals, providing immediate protection and reducing main chain breakage; antioxidant 168 decomposes peroxides, blocking the free radical regeneration cycle, inhibiting high-temperature discoloration, and extending the shelf life of antioxidant 1010; DLTP provides long-term stability. The mixing ratio range has been experimentally verified, with the upper limit preventing precipitation and the lower limit ensuring aging performance; in particular, the synergistic effect of antioxidant 1010 and antioxidant 168, where antioxidant 168 decomposes hydrogen peroxides to reduce the consumption of antioxidant 1010, achieves triple protection against radiation, heat and oxygen, and discoloration, achieving an ultimate balance of performance, cost, and lifespan under the harsh 105℃ irradiation environment.

[0024] Secondly, this application provides a method for preparing a 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulating material, employing the following technical solution: S1 compounding and granulation: The matrix resin, composite flame retardant, sensitizer, compatibilizer, antioxidant, lubricant, silane coupling agent and dispersant are added to a co-rotating parallel twin-screw extruder. The temperature is controlled in zones, with the temperature controlled at ≤190℃. After vacuum degassing, the mixture is extruded and granulated. S2 gradient electron beam irradiation: Pre-irradiation: 75-85 kGy, accelerating voltage 1.8-2.2 MeV, beam current 8-12 mA; Final irradiation: 65-75 kGy, accelerating voltage 1.3-1.7 MeV, beam current 7-9 mA. S3 post-treatment: After irradiation, the particles are vacuum dried at 60-80℃ for 5-6 hours, with a moisture content ≤0.3%.

[0025] By adopting the above scheme, the maximum mixing temperature of S1 is ≤190℃, protecting the activity of the sensitizer TMPTMA, with a residual rate of ≥95%, effectively removing small molecule volatiles (such as silane hydrolysis byproducts), and reducing bubbles and defects; S2 gradient electron beam irradiation, pre-irradiation: high-energy electron beam (1.8-2.2MeV) ensures the formation of the initial cross-linking network inside the thick material, laying the foundation for subsequent irradiation, and high-dose pre-irradiation stimulates the activity of the sensitizer and accelerates the free radical reaction; final irradiation, reducing energy to avoid excessive irradiation damage, focusing on increasing the surface cross-linking density, forming a gradient cross-linking structure, taking into account both mechanical strength and flexibility, beam current control (7-9 mA) reduces local overheating caused by heat accumulation, and maintains the dimensional stability of the material; S3 post-treatment, vacuum drying, thoroughly removes low molecular weight debris and residual moisture generated by irradiation to prevent the decline in insulation performance; low-temperature drying conditions maintain the stability of the cross-linking structure, ensure the electrical insulation performance of the final product, and avoid secondary degradation. The advantages of gradient irradiation include uniform cross-linking of the network, avoiding stress concentration issues associated with single high-dose irradiation, improving material heat resistance (long-term use at 105℃) and crack resistance, enhancing flame retardant stability, and reducing the risk of lattice damage to inorganic flame retardants through stepwise irradiation. Through synergistic optimization of the entire process—mixing, irradiation, and post-treatment—it solves problems such as difficult processing, uneven cross-linking, and poor thermal stability of highly filled halogen-free flame retardant materials. It is suitable for manufacturing high-end wire and cable insulation layers, combining high efficiency, environmental friendliness, and high reliability.

[0026] Preferably, in the S1 mixing and granulation, the matrix resin and lubricant are added from the main feed port; the composite flame retardant, compatibilizer, silane coupling agent and dispersant are added from the side feed port in the middle of the melting section; and the sensitizer and antioxidant are injected from the liquid injection port of the mixing section.

[0027] By adopting the above scheme, the matrix resin and lubricant are added through the main feed port to prevent the lubricant from prematurely encapsulating the flame retardant and affecting its dispersibility, ensuring that the resin is fully melted and plasticized. Flame retardants and compatibilizers are added through the middle side feed port, utilizing the high temperature of the melting section to initially form the resin melt before introducing fillers, reducing screw wear. Simultaneously, the synergistic effect of silane coupling agents and dispersants ensures uniform dispersion of the high-filling-weight flame retardant, preventing agglomeration. Sensitizers and antioxidants are injected in liquid form into the mixing section to prevent premature decomposition at high temperatures. The 180℃ mixing section ensures their uniform distribution, improving the efficiency of subsequent irradiation crosslinking.

[0028] Preferably, the temperature of the S1 mixing and granulation is controlled in zones: feeding section: 80-100℃, melting section: 160-180℃, mixing section: 180-190℃, vacuum devolatilization section: 190℃, vacuum degree: -0.08 to -0.10 MPa, and die head: 170-175℃.

[0029] Preferably, the screw speed of the S1 mixing and granulation is 250-350 rpm, the material residence time is 1.8-2.5 min, and the melt pressure is 8-12 MPa.

[0030] By adopting the above scheme, vacuum devolatilization effectively removes small molecule volatiles, reducing bubbles and defects; high screw speed and short residence time balance dispersion efficiency and thermal history control, preventing resin degradation; melt pressure ensures dense plasticization and avoids flame retardant sedimentation.

[0031] Thirdly, this application provides the application of a 105°C low-smoke halogen-free irradiated cross-linked polyolefin insulation material in B1-grade flame-retardant cables.

[0032] By adopting the above scheme, the cable meets the B1 level requirements of GB 31247-2014 standard, with a burning growth rate index FIGRA ≤ 89 W / s; total heat release (THR) 1200s ≤ 9.2 MJ; and a heat transfer rate (SPR) ≤ 0.09 m. 2 / s; Electrical and mechanical properties: dielectric strength ≥25kV / mm, elongation at break ≥350%, volume resistivity (105℃) ≥2.8×10 15 Ω·m.

[0033] In summary, this application has the following beneficial effects: 1. The 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulation material prepared in this application has a ternary blend of matrix resin to balance rigidity and flexibility, and high filling and interface modification of composite flame retardant to achieve excellent flame retardant and mechanical properties. The compounded sensitizer reduces the cost of irradiation process. Through multi-component synergistic design, this formula significantly improves temperature resistance, mechanical strength and processing performance while maintaining low-smoke halogen-free environmental protection characteristics, and has both high safety and long service life.

[0034] 2. The preparation method of the 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulation material of this application solves the problems of difficult processing, uneven crosslinking, and poor thermal stability of high-filler halogen-free flame retardant materials through the synergistic optimization of the entire process of mixing-irradiation-post-treatment. It is suitable for the manufacturing of high-end wire and cable insulation layers and has the advantages of high efficiency, environmental protection and high reliability. The gradient irradiation can uniformly crosslink the network, avoid the stress concentration problem of single high-dose irradiation, improve the heat resistance (long-term use at 105℃) and crack resistance of the material, and enhance the stability of the flame retardant. The step-by-step irradiation reduces the risk of lattice damage of inorganic flame retardants.

[0035] 3. The application of the 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulation material of this application in B1-grade flame-retardant cables produces cables that meet the B1-grade requirements of GB 31247-2014 standard, with a burning growth rate index FIGRA ≤ 89 W / s; total heat release (THR) 1200s ≤ 9.2 MJ; and a flame retardancy rate (SPR) ≤ 0.09 m.2 / s; Electrical and mechanical properties: dielectric strength ≥25kV / mm, elongation at break ≥350%, volume resistivity (105℃) ≥2.8×10 15 Ω·m. Detailed Implementation

[0036] The technical solution of this application is further illustrated by specific embodiments below. These specific embodiments do not represent a limitation on the scope of protection of this application. Any non-essential modifications and adjustments made by others based on the concept of this application still fall within the scope of protection of this application.

[0037] Unless otherwise specified, the experimental methods shown in the following examples are conventional methods. All reagents and materials shown are commercially available products.

[0038] High-density polyethylene (HDPE): Shengchuang Petrochemical (Shanghai) Co., Ltd., Item No.: B6561; Polyolefin elastomer (POE): Dow Chemical, USA, grade: 8411; LLDPE metallocene (abbreviated mLLDPE): Exxon Chemicals, catalog number: 3518CB; Trimethylolpropane trimethacrylate (TMPTMA): Zhongshan Dixing Chemical Co., Ltd., Product No.: HS071322, CAS No.: 3290-92-4, Purity: 99%; Silicone masterbatch; Dongguan Shanyi Plastics Co., Ltd., Brand: Lanzhu, Material: PE; Ethylene-methyl acrylate copolymer (EMA): DuPont, USA, grade: AC1218; Paraffin wax: Guangzhou Fufeng Chemical Technology Co., Ltd., model YTSL, grade 300#; Oxidized polyethylene wax (OPE wax): Honeywell, product model: AC 316A; Styrene (abbreviated ST); Shandong Ruitianxiang New Materials Co., Ltd., CAS: 100-42-5, Item No.: 2021.12.23.1; Antioxidant 1010: Dongguan Shanyi Plastics Co., Ltd., product number 1010, CAS: 6683-19-8; Antioxidant 168: Dongguan Shanyi Plastics Co., Ltd., product number 168, CAS: 31570-04-4; Antioxidant DLTP: Shanghai Huafutai Chemical Co., Ltd., CAS123-28-4, Product No.: 123-28-4.

[0039] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0040] Preparation Example Preparation Example 1: Preparation of Composite Flame Retardants 4 kg of KH-550 was dissolved in 32 kg of anhydrous ethanol and sprayed onto 100 kg of magnesium hydroxide powder. The mixture was then treated in a high-speed mixer at 3000 rpm for 15 min and vacuum dried at 60 °C until the moisture content was ≤0.5% to obtain pretreated magnesium hydroxide. The pretreated magnesium hydroxide, 10 kg of vinyl phosphonate monomer, and 0.4 kg of APS initiator were added to a reactor and heated to 80 °C under nitrogen protection. The mixture was stirred for 2 h and the product was washed three times with ethanol and dried at 80 °C to obtain the vinyl phosphonate graft product. The vinyl phosphonate graft product and 13 kg of zinc borate were mixed in a high-speed mixer and heated to 180 °C for cladding for 10 min. After cooling, the mixture was pulverized and sieved through a 400-mesh sieve.

[0041] Preparation Example 2: Preparation of Composite Flame Retardants Similar to Preparation Example 1, except that the amount of raw materials added during the preparation process is: 100 kg of nano magnesium hydroxide, 3 kg of KH550, 24 kg of anhydrous ethanol, 8 kg of vinyl phosphonate monomer, 0.3 kg of APS initiator and 10 kg of zinc borate.

[0042] Preparation Example 3: Preparation of Composite Flame Retardants Similar to Preparation Example 1, except that the amount of raw materials added during the preparation process is: 100 kg of nano magnesium hydroxide, 5 kg of KH550, 40 kg of anhydrous ethanol, 12 kg of vinyl phosphonate monomer, 0.5 kg of APS initiator and 15 kg of zinc borate.

[0043] Preparation Example 4: Preparation of POE-g-MAH 100 kg POE, 2.0 kg maleic anhydride, 0.2 kg dicumyl peroxide, and 0.8 kg styrene were added to a high-speed mixer and mixed at 70°C for 5 min. The mixture was then fed into a twin-screw extruder with the screw temperature controlled in the following zones: feeding zone: 90°C, melting zone: 170°C, reaction zone: 180°C, and vacuum devolatilization zone: -0.08 MPa. The screw speed was 300 rpm, and the residence time was 2 min. The extruded strip was water-cooled and pelletized, and then vacuum-dried at 70°C for 4 h to obtain POE-g-MA.

[0044] Preparation Example 5: Preparation of POE-g-MAH 100 kg POE, 1.5 kg maleic anhydride, 0.1 kg dicumyl peroxide, and 0.5 kg styrene were added to a high-speed mixer and mixed at 60°C for 5 min. The mixture was then fed into a twin-screw extruder with the screw temperature controlled in the following zones: feeding zone: 80°C, melting zone: 160°C, reaction zone: 180°C, and vacuum devolatilization zone: -0.08 MPa. The screw speed was 400 rpm, and the residence time was 1.5 min. The extruded strip was water-cooled and pelletized, and then vacuum-dried at 70°C for 4 h to obtain POE-g-MA.

[0045] Preparation Example 6: Preparation of POE-g-MAH 100 kg POE, 3.0 kg maleic anhydride, 0.3 kg dicumyl peroxide, and 1.0 kg styrene were added to a high-speed mixer and mixed at 80°C for 5 min. The mixture was then fed into a twin-screw extruder, with the screw temperature controlled in the following zones: feeding zone: 100°C, melting zone: 180°C, reaction zone: 190°C, and vacuum devolatilization zone: -0.08 MPa. The screw speed was 200 rpm, and the residence time was 2.5 min. The extruded strip was water-cooled and pelletized, and then vacuum-dried at 70°C for 4 h to obtain POE-g-MA.

[0046] Preparation Example 7: Preparation of EMA-g-MAH 100 kg EMA, 2 kg maleic anhydride, 0.2 kg dicumyl peroxide, and 0.9 kg styrene were added to a high-speed mixer and mixed at 80 °C for 5 min. The mixture was then fed into a twin-screw extruder, with the screw temperature controlled in the following zones: feeding zone: 90 °C, melting zone: 170 °C, reaction zone: 190 °C, and vacuum devolatilization zone: -0.08 MPa. The screw speed was 300 rpm, and the residence time was 25 min. The extruded strip was water-cooled and pelletized, and then vacuum-dried at 70 °C for 4 h to obtain EMA-g-MAH.

[0047] Preparation Example 8: Preparation of EMA-g-MAH 100 kg EMA, 1.5 kg maleic anhydride, 0.1 kg dicumyl peroxide, and 0.5 kg styrene were added to a high-speed mixer and mixed at 70 °C for 5 min. The mixture was then fed into a twin-screw extruder with the screw temperature controlled in the following zones: feeding zone: 85 °C, melting zone: 160 °C, reaction zone: 180 °C, and vacuum devolatilization zone: -0.08 MPa. The screw speed was 200 rpm, and the residence time was 2.5 min. The extruded strip was water-cooled and pelletized, and then vacuum-dried at 70 °C for 4 h to obtain EMA-g-MAH.

[0048] Preparation Example 9: Preparation of EMA-g-MAH 100 kg EMA, 2.5 kg maleic anhydride, 0.3 kg dicumyl peroxide, and 1.0 kg styrene were added to a high-speed mixer and mixed at 85°C for 5 min. The mixture was then fed into a twin-screw extruder with the screw temperature controlled in the following zones: feeding zone: 95°C, melting zone: 175°C, reaction zone: 190°C, and vacuum devolatilization zone: -0.08 MPa. The screw speed was 400 rpm, and the residence time was 1.5 min. The extruded strip was water-cooled and pelletized, and then vacuum-dried at 70°C for 4 h to obtain EMA-g-MAH.

[0049] Example

[0050] Example 1 A method for preparing a 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulating material, employing the following technical solution: S1 Compounding and Granulation: Raw materials are fed into a co-rotating parallel twin-screw extruder. The matrix resin and lubricant are added through the main feed inlet, while the composite flame retardant, compatibilizer, silane coupling agent, and dispersant are added through the side feed inlet in the middle of the melting section. Sensitizers and antioxidants are injected through the liquid injection port in the compounding section. Temperature is controlled in zones: feeding section: 90℃, melting section: 170℃, compounding section: 180℃, vacuum devolatilization section: 190℃, vacuum degree: -0.09MPa, die head: 175℃; screw speed: 300rpm, material residence time: 2.0min, melt pressure: 10MPa; extrusion granulation. S2 gradient electron beam irradiation: Pre-irradiation: 80 kGy, accelerating voltage 2.0 MeV, beam current 10 mA; Final irradiation: 70 kGy, accelerating voltage 1.5 MeV, beam current 8 mA. S3 post-treatment: After irradiation, the particles are vacuum dried at 70℃ for 5 hours, with a moisture content ≤0.3%.

[0051] The amounts of each raw material added in Examples 1-6 are shown in Table 1.

[0052]

[0053] The composite flame retardant was prepared according to the method of Preparation Example 1; the compatibilizer was prepared according to the method of Preparation Example 4.

[0054] Example 2 Similar to Example 1, except that a method for preparing a 105°C low-smoke halogen-free irradiated crosslinked polyolefin insulating material adopts the following technical solution: S1 Compounding and Granulation: Raw materials are fed into a co-rotating parallel twin-screw extruder. The matrix resin and lubricant are added through the main feed inlet, while the composite flame retardant, compatibilizer, silane coupling agent, and dispersant are added through the side feed inlet in the middle of the melting section. Sensitizers and antioxidants are injected through the liquid injection port in the compounding section. Temperature is controlled in zones: feeding section: 80℃, melting section: 160℃, compounding section: 180℃, vacuum devolatilization section: 190℃, vacuum degree: -0.08MPa, die head: 170℃. Screw speed is 250rpm, material residence time is 2.5min, melt pressure is 8MPa; extrusion granulation is then performed. S2 gradient electron beam irradiation: Pre-irradiation: 75 kGy, accelerating voltage 1.8 MeV, beam current 8 mA; Final irradiation: 65 kGy, accelerating voltage 1.3 MeV, beam current 7 mA. S3 post-treatment: After irradiation, the particles are vacuum dried at 60℃ for 5 hours, with a moisture content ≤0.3%.

[0055] The amounts of each raw material are shown in Table 1.

[0056] Example 3 Similar to Example 1, except that a method for preparing a 105°C low-smoke halogen-free irradiated crosslinked polyolefin insulating material adopts the following technical solution: S1 Compounding and Granulation: Raw materials are fed into a co-rotating parallel twin-screw extruder. The matrix resin and lubricant are added through the main feed inlet, while the composite flame retardant, compatibilizer, silane coupling agent, and dispersant are added through the side feed inlet in the middle of the melting section. Sensitizers and antioxidants are injected through the liquid injection port in the compounding section. Temperature is controlled in zones: feeding section: 100℃, melting section: 180℃, compounding section: 190℃, vacuum devolatilization section: 190℃, vacuum degree: -0.10 MPa, die head: 175℃; screw speed: 350 rpm, material residence time: 2.5 min, melt pressure: 12 MPa; extrusion granulation. S2 gradient electron beam irradiation: Pre-irradiation: 85 kGy, accelerating voltage 2.2 MeV, beam current 12 mA; Final irradiation: 75 kGy, accelerating voltage 1.7 MeV, beam current 9 mA. S3 post-treatment: After irradiation, the particles are vacuum dried at 80℃ for 6 hours, with a moisture content ≤0.3%.

[0057] The amounts of each raw material are shown in Table 1.

[0058] Example 4 Similar to Example 1, except that the amounts of each raw material are shown in Table 1; the composite flame retardant is prepared according to the method of Preparation Example 2; and the compatibilizer is prepared according to the method of Preparation Example 5.

[0059] Example 5 Similar to Example 1, except that the amounts of each raw material are shown in Table 1; the composite flame retardant is prepared according to the method of Preparation Example 3; and the compatibilizer is prepared according to the method of Preparation Example 6.

[0060] Example 6 Similar to Example 1, except that the amounts of each raw material are as shown in Table 1; the composite flame retardant is prepared according to the method of Preparation Example 1; and the compatibilizer EMA-g-MAH is prepared according to the method of Preparation Example 7.

[0061] Example 7 Similar to Example 1, except that the composite flame retardant was prepared according to the method of Preparation Example 2; and the compatibilizer EMA-g-MAH was prepared according to the method of Preparation Example 8.

[0062] Example 8 Similar to Example 1, except that the amounts of each raw material are as shown in Table 1; the composite flame retardant is prepared according to the method of Preparation Example 3; and the compatibilizer EMA-g-MAH is prepared according to the method of Preparation Example 9.

[0063] Comparative Example Comparative Example 1 Similar to Example 1, except that no compatibilizer is added to the raw materials.

[0064] Comparative Example 2 Similar to Example 1, except that no silicone masterbatch is added to the raw materials.

[0065] Comparative Example 3 Similar to Example 1, except that the composite flame retardant in the raw materials was not treated, and only nano-magnesium hydroxide and zinc borate were physically mixed.

[0066] Comparative Example 4 Similar to Example 1, except that the S2 gradient electron beam irradiation process in the preparation process is cancelled and replaced with a single irradiation of 150 kGy.

[0067] Comparative Example 5 Similar to Example 1, except that the preparation process S1 is mixing and granulation, with a feeding section of 120°C, a melting section of 210°C, and a mixing section of 190°C.

[0068] Comparative Example 6 Similar to Example 1, except that the proportion of lubricant in the raw materials is adjusted to: 1.5 kg of paraffin wax and 0.5 kg of OPE.

[0069] Comparative Example 7 Similar to Example 1, except that no compatibilizer is added to the raw materials, which are replaced with POE.

[0070] Comparative Example 8 Similar to Example 1, except that the raw materials lack antioxidants.

[0071] Comparative Example 9 Similar to Example 1, except that the preparation process S1 is mixed and granulated, the vacuum devolatilization section is omitted, and the vacuum degree is 0 MPa.

[0072] Comparative Example 10 Similar to Example 1, except that only 100 kg of HDPE was used as the matrix resin in the raw materials, and the addition of POE and mLLDPE was removed.

[0073] Performance testing Cables were prepared using low-smoke halogen-free irradiated cross-linked polyolefin insulation materials prepared at 105℃ using Examples 1-8 and Comparative Examples 1-10. The specific cable preparation method is as follows: oxygen-free copper wire was drawn, annealed, cleaned, and dried. The insulation material was extruded through a three-layer co-extrusion extruder at a controlled temperature of 100-150℃, an extrusion speed of 20-30 m / min, and an insulation thickness of 0.77-0.80 mm. Electron beam irradiation cross-linking was performed at 150 kGy, an accelerating voltage of 1.5-2.0 MeV, and a beam current of 10-15 mA. After cooling and shaping, the cable was obtained.

[0074] Based on the requirements of Class B1 in GB 31247-2014 "Classification of Flammability of Cables and Optical Fibers", and considering the characteristics of the insulation material, electrical and mechanical performance tests are added: the test items and the standards are shown in Table 2.

[0075]

[0076] The performance test results of the 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulating materials prepared by Examples 1-8 and Comparative Examples 1-10 are shown in Table 3-4.

[0077]

[0078]

[0079] As shown in Tables 3-4, the cables prepared using the 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulation materials prepared in Examples 1-8 meet the requirements of Class B1 in GB 31247-2014 "Classification of Burning Performance of Cables and Optical Fibers". Combined with additional electromechanical performance tests based on the insulation material characteristics, the following results are achieved: burning growth rate index FIGRA ≤ 89 W / s; total heat release (THR) 1200s ≤ 5.4 MJ; and smoke production rate index ≤ 20 m. 2 / s 2Electrical and mechanical properties: dielectric strength ≥25kV / mm, elongation at break ≥350%, volume resistivity (105℃) ≥2.8×10⁻⁶. 15 The cable has a strength of Ω·m and meets the requirements of Class B1 in GB 31247-2014 standard, exhibiting excellent performance.

[0080] In Comparative Example 1, no compatibilizer was added to the raw materials, causing the flame retardant to agglomerate and form heat conduction channels, resulting in a dramatic increase in THR 1200s to 19.5 MJ. Simultaneously, interface defects were observed, leading to a volume resistivity of 0.5 × 10⁻⁶. 15 Ω·m, agglomerates become leakage paths; in Comparative Example 2, without the addition of silicone masterbatch, the dielectric strength decreased to 20.2 kV / mm, the melt fractured, and crosslinking was inhibited, lacking siloxane free radical catalysis; in Comparative Example 3, the composite flame retardant in the raw material was not treated, only physical mixing of nano-magnesium hydroxide and zinc borate was performed; it did not meet the standards, and the barrier failed; in Comparative Example 4, the S2 gradient electron beam irradiation in the preparation process was canceled and replaced with a single irradiation of 150 kGy; the heat release was concentrated, and the total heat release THR1200s was 16.8 MJ exceeding the limit; in Comparative Example 5, the S1 mixing and granulation process was carried out, with the feeding section at 120℃, the melting section at 210℃, and the mixing section at 190℃; high-temperature mixing caused TMPTMA decomposition and uneven distribution of the flame retardant; in Comparative Example 6, the lubricant ratio in the raw material was adjusted; paraffin wax precipitated, and the volume resistivity was 1.8 × 10 15 The flame spread of Comparative Example 7 was 1.8m, and the TSP exceeded the limit. The raw materials of Comparative Example 8 lacked antioxidants, which accelerated thermal aging. The preparation process of Comparative Example 9 involved S1 mixing and granulation, eliminating the vacuum devolatilization section, resulting in a vacuum degree of 0 MPa and the release of benzo[a]pyrene during combustion. The raw materials of Comparative Example 10 used only 100kg of HDPE as the matrix resin, removing the addition of POE and mLLDPE, resulting in brittle fracture, reduced impact strength, accelerated flame spread of cracks, and shrinkage cracking at high temperatures.

[0081] The above experimental results show that the 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulation material prepared in this application has the following properties: HDPE matrix resin maintains a rigid skeleton to ensure high-temperature strength at 105℃; LLDPE metallocene, with long-chain branches, enhances melt strength, effectively improves extrusion surface smoothness, and reduces the risk of melt fracture; POE imparts extremely low-temperature toughness, with an impact retention rate of ≥85% at -40℃, while also improving the uniformity of irradiation crosslinking; and the melt index is stabilized at 1.5-2.0 g / 10min (190℃) through ternary blending of HDPE, metallocene polyethylene, and POE, avoiding the delamination phenomenon of traditional HDPE and POE systems under high shear. TMPTMA in the sensitizer accelerates the crosslinking reaction and shortens the irradiation time; the silicone masterbatch has both lubricating and sensitizing functions, reducing the coefficient of friction. The compatibilizer POE-g-MAH enhances the interfacial bonding between the flame retardant and resin, preventing stress cracking; and EMA-g-MAH improves the compatibility of polar EMA segments with the flame retardant, reducing interfacial defects. The lubricant combination helps to balance internal and external lubrication. Paraffin wax provides external lubrication, forming a molecular layer at the interface between the melt and the equipment, and it also resists oxidation and migration. Oxidized polyethylene wax provides internal lubrication, with long-chain alkanes penetrating the polymer chain to reduce intermolecular entanglement. At the same time, the carboxyl groups of oxidized polyethylene wax synergistically enhance the bonding force between the flame retardant and the resin with the compatibilizer. Silane coupling agents react with the outer -OH layer of the flame retardant to improve its hygrothermal stability. Dispersants effectively prevent the flame retardant from absorbing moisture and agglomerating. By employing a synergistic approach combining composite flame retardants, sensitized lubricants, and metallocene processing enhancements, the existing problems of radiation-crosslinked low-smoke halogen-free polyolefin insulation materials in terms of heat resistance, flexibility, processability, flame retardant efficiency, long-term aging performance, and cost have been resolved. The application of 105℃ low-smoke halogen-free radiation-crosslinked polyolefin insulation material in B1-grade flame-retardant cables meets the B1-grade requirements of GB 31247-2014 standard, with a burning growth rate index FIGRA ≤ 89 W / s; total heat release (THR) ≤ 9.2 MJ over 1200 s; and a flame retardant velocity (SPR) ≤ 0.09 m³ / s. 2 / s; Electrical and mechanical properties: dielectric strength ≥25kV / mm, elongation at break ≥350%, volume resistivity (105℃) ≥2.8×10 15 Ω·m.

[0082] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the present invention, they are protected by patent law.

Claims

1. A low-smoke, halogen-free irradiated cross-linked polyolefin insulating material at 105℃, characterized in that, It is prepared from the following raw materials in parts by weight: 100 parts of matrix resin, 100-130 parts of composite flame retardant, 2-4 parts of sensitizer, 3-8 parts of compatibilizer, 0.6-2 parts of antioxidant, 2.0-2.5 parts of lubricant, 0.8-1.0 parts of silane coupling agent and 0.4-0.6 parts of dispersant; The matrix resin is HDPE, LLDPE, metallocene, and POE in a weight ratio of (4-6):(2-3):(2-3). The sensitizer is TMPTMA and silicone masterbatch in a weight ratio of (1-2.5):(1-1.5). The lubricant is paraffin wax and oxidized polyethylene wax in a weight ratio of (1-1.5):1; The silane coupling agent is coupling agent 172; The dispersant is zinc stearate.

2. The 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulating material according to claim 1, characterized in that, The composite flame retardant, The preparation process includes the following steps: pretreating nano-magnesium hydroxide with silane coupling agent KH-550, adding vinyl phosphonate monomer and APS initiator, carrying out a grafting reaction, adding zinc borate, mixing in a high-speed mixer, heating to melt and coat the surface, cooling, and then pulverizing and sieving.

3. The 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulating material according to claim 2, characterized in that, The composite flame retardant is composed of nano magnesium hydroxide, KH550, vinyl phosphonate monomer, APS initiator and zinc borate in a weight ratio of 100:(3-5):(8-12):(0.3-0.5):(10-15).

4. The 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulating material according to claim 1, characterized in that, The compatibilizer is either POE-g-MAH or EMA-g-MAH; its grafting rate is 1.2-1.6wt%; at 190℃ and 2.16kg, its melt index is 2-8g / 10min; and its acid value is 8-15mg KOH / g.

5. The 105℃ low-smoke halogen-free irradiated cross-linked polyolefin insulating material according to claim 1, characterized in that, The antioxidant is antioxidant 1010, antioxidant 168 and DLTP in a weight ratio of (0.2-1.0):(0.2-0.6):(0.2-0.4).

6. A method for preparing a 105°C low-smoke halogen-free irradiated crosslinked polyolefin insulating material as described in any one of claims 1-5, characterized in that, It includes the following steps: S1 compounding and granulation: The matrix resin, composite flame retardant, sensitizer, compatibilizer, antioxidant, lubricant, silane coupling agent and dispersant are added to a co-rotating parallel twin-screw extruder. The temperature is controlled in zones, with the temperature controlled at ≤190℃. After vacuum degassing, the mixture is extruded and granulated. S2 gradient electron beam irradiation: Pre-irradiation: 75-85 kGy, accelerating voltage 1.8-2.2 MeV, beam current 8-12 mA; Final irradiation: 65-75 kGy, accelerating voltage 1.3-1.7 MeV, beam current 7-9 mA. S3 post-treatment: After irradiation, the particles are vacuum dried at 60-80℃ for 5-6 hours, with a moisture content ≤0.3%.

7. The method for preparing the 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulating material according to claim 6, characterized in that, In the S1 compounding and granulation process, the matrix resin and lubricant are added from the main feed port; the composite flame retardant, compatibilizer, silane coupling agent and dispersant are added from the side feed port in the middle of the melting section; and the sensitizer and antioxidant are injected from the liquid injection port of the compounding section.

8. The method for preparing the 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulating material according to claim 6, characterized in that, The temperature zone control of the S1 mixing and granulation is as follows: feeding section: 80-100℃, melting section: 160-180℃, mixing section: 180-190℃, vacuum devolatilization section: 190℃, vacuum degree: -0.08 to -0.10 MPa, and die head: 170-175℃.

9. The method for preparing the 105℃ low-smoke halogen-free irradiated crosslinked polyolefin insulating material according to claim 6, characterized in that, The screw speed of the S1 compounding and granulation process is 250-350 rpm, the material residence time is 1.8-2.5 min, and the melt pressure is 8-12 MPa.

10. The application of a 105°C low-smoke halogen-free irradiated cross-linked polyolefin insulation material as described in claim 1 in B1 grade flame-retardant cables.

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