Low-smoke halogen-free 105 deg.c. ultraviolet light irradiation cross-linking grade insulating material and preparation method thereof

Abstract

The application discloses low-smoke halogen-free 105 DEG C ultraviolet light irradiation crosslinking grade insulating material and a preparation method thereof. According to weight parts, the insulating material is mainly made of 20-60 parts of ethylene-vinyl acetate copolymer, 10-50 parts of polyolefin elastomer, 50-100 parts of halogen-free flame retardant, 1-4 parts of photoinitiator, 0.2-2.5 parts of crosslinking accelerator, 0.2-1.5 parts of antioxidant, 0.1-0.9 parts of weather-resistant agent and 0.5-3.5 parts of processing aid. The insulating material is stable in long-term use at 105 DEG C high temperature, and meanwhile, the insulating material has excellent mechanical properties, flame retardant properties, processing fluidity and weather resistance, and is low-smoke halogen-free ultraviolet light irradiation crosslinking grade insulating material.

Description

Invention Field

[0001] This invention relates to a low-smoke, halogen-free, 105°C ultraviolet irradiation cross-linked insulating material and its preparation method, belonging to the field of wire and cable insulation material technology. Technical Background

[0002] With the rapid development of rail transit, high-rise buildings, shipbuilding, marine engineering, and new energy, the requirements for the safety performance, temperature resistance, and environmental protection of wires and cables are becoming increasingly stringent. Low-smoke halogen-free insulation materials, because they do not release toxic hydrogen halide gas or large amounts of smoke when burned, have gradually replaced traditional halogen-containing insulation materials and have become one of the mainstream development directions for insulation materials.

[0003] For applications requiring operating temperatures up to 105°C, such as automotive wiring harnesses and instrument wiring harnesses in high-temperature environments, ordinary thermoplastic low-smoke halogen-free insulation materials often suffer from insufficient heat distortion temperature and rapid degradation of mechanical properties under long-term high temperatures, making it difficult to meet usage requirements. To improve the high-temperature resistance of materials, cross-linking technology is widely used. Through cross-linking reactions, a three-dimensional network structure is formed, which can significantly improve the thermal stability, aging resistance, and mechanical strength of the material.

[0004] Currently, the main crosslinking methods for low-smoke halogen-free insulation materials include chemical crosslinking and radiation crosslinking. Chemical crosslinking requires the addition of crosslinking agents (such as peroxides) to initiate the crosslinking reaction at high temperatures, but it suffers from drawbacks such as the decomposition products of the crosslinking agent affecting the material's environmental performance, poor crosslinking uniformity, and a narrow processing window. Radiation crosslinking mainly includes electron beam irradiation and ultraviolet irradiation. Electron beam irradiation offers high crosslinking energy and fast crosslinking efficiency, but it requires large equipment investment, has high operating costs, and is subject to certain limitations on material thickness, making it unsuitable for processing complex cable structures.

[0005] Ultraviolet (UV) irradiation crosslinking technology has become a research hotspot in recent years due to its advantages such as low equipment investment, low energy consumption, flexible processing, and continuous production. However, existing UV irradiation crosslinked low-smoke halogen-free insulation materials still face many challenges in long-term use at 105℃: First, there is the problem of balancing crosslinking efficiency and material mechanical properties. To improve the crosslinking speed, a large amount of photoinitiator is often added, which can easily lead to a decrease in tensile strength and a deterioration in aging resistance. Second, it is difficult to balance the flame retardancy and processing fluidity of the low-smoke halogen-free system. The addition of a large amount of flame retardant will reduce the melt flow rate of the material, affecting the extrusion molding quality of the cable. Third, the material's UV aging resistance is insufficient. After long-term use, it is prone to surface cracking and insulation performance degradation, which restricts its application in outdoor or high-temperature environments.

[0006] In summary, existing low-smoke halogen-free ultraviolet irradiation cross-linked insulating materials have the following problems: 1. Insufficient high temperature resistance: The heat distortion temperature of ordinary low-smoke halogen-free ultraviolet irradiation cross-linked insulation materials is mostly below 100℃. When used for a long time at a high temperature of 105℃, they are prone to softening and deformation, resulting in a significant decrease in mechanical and insulation properties. 2. Imbalance between crosslinking efficiency and performance: Excessive use of photoinitiator leads to reduced mechanical strength and poor aging resistance of the material, while insufficient use results in inadequate crosslinking and failure to meet high temperature resistance requirements; 3. Conflict between processing and flame retardant performance: The large amount of flame retardant added makes the material flow poor during processing, and problems such as surface roughness and eccentricity are easy to occur during extrusion molding, which affects the quality of cable products; 4. Poor weather resistance: When exposed to ultraviolet light or high temperature for a long time, the material is prone to aging and degradation, and the surface will crack and powder, and the insulation resistance will decrease, posing a safety hazard.

[0007] Therefore, it is of great significance to invent a low-smoke halogen-free ultraviolet irradiation cross-linked insulating material that can be used stably at a high temperature of 105℃ for a long time, while also taking into account excellent mechanical properties, flame retardant properties, processing fluidity and weather resistance. Summary of the Invention: The purpose of this invention is to provide a low-smoke, halogen-free, 105°C ultraviolet irradiation cross-linked insulating material and its preparation method. The insulating material exhibits long-term stable use at 105°C while also possessing excellent mechanical properties, flame retardant properties, processing fluidity, and weather resistance.

[0008] To solve the above technical problems, the present invention adopts the following technical solution: The low-smoke, halogen-free, 105℃ ultraviolet irradiation cross-linked insulating material, by weight, is mainly composed of 20-60 parts of ethylene-vinyl acetate copolymer (EVA), 10-50 parts of polyolefin elastomer (POE), 50-100 parts of halogen-free flame retardant, 1-4 parts of photoinitiator, 0.2-2.5 parts of cross-linking accelerator, 0.2-1.5 parts of antioxidant, 0.1-0.9 parts of weathering agent, and 0.5-3.5 parts of processing aid.

[0009] The aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked grade insulation material, calculated by weight, is mainly composed of 30-50 parts of ethylene-vinyl acetate copolymer (EVA), 20-40 parts of polyolefin elastomer (POE), 60-90 parts of halogen-free flame retardant, 1.5-3 parts of photoinitiator, 0.5-2 parts of cross-linking accelerator, 0.3-1 part of antioxidant, 0.2-0.8 parts of weathering agent, and 1-3 parts of processing aid.

[0010] Specifically, the aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked grade insulation material is mainly composed of 40 parts of ethylene-vinyl acetate copolymer (EVA), 30 parts of polyolefin elastomer (POE), 75 parts of halogen-free flame retardant, 3 parts of photoinitiator, 1 part of cross-linking accelerator, 1 part of antioxidant, 0.6 parts of weathering agent, and 2 parts of processing aid, calculated by weight.

[0011] In the aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation crosslinking grade insulation material, the halogen-free flame retardant, calculated by weight, mainly consists of magnesium hydroxide and aluminum hydroxide in a weight ratio of 2:1-3:1; the polyolefin elastomer is an ethylene-octene copolymer with a melt index of 1-5 g / 10 min (190℃, 2.16 kg); the magnesium hydroxide is ultrafine active magnesium hydroxide with a particle size of 1-5 μm, and its surface is modified with a silane coupling agent; the aluminum hydroxide is ultrafine aluminum hydroxide with a particle size of 2-8 μm.

[0012] In the aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation crosslinking grade insulation material, the photoinitiator, calculated by weight, mainly consists of acetophenone-based and thioxanthone-based photoinitiators in a weight ratio of 3:1-4:1; the acetophenone-based photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the thioxanthone-based photoinitiator is isopropylthioxanthone.

[0013] In the aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation crosslinking grade insulation material, the crosslinking accelerator is trimethylolpropane triacrylate (TMPTA) or pentaerythritol triacrylate (PETA).

[0014] In the aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked grade insulation material, the antioxidant, calculated by weight, mainly consists of hindered phenolic antioxidants and phosphite antioxidants in a weight ratio of 1:1.

[0015] In the aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked grade insulation material, the weathering agent, calculated by weight, mainly consists of ultraviolet absorber and hindered amine light stabilizer (HALS), with a weight ratio of 2:1.

[0016] In the aforementioned low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked grade insulation material, the processing aids, calculated by weight, are mainly composed of zinc stearate and polyethylene wax in a weight ratio of 1:1 to 1:2.

[0017] The aforementioned method for preparing low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material includes the following steps: Step 1: Premixing. Weigh out EVA, POE, halogen-free flame retardant, antioxidant, weathering agent, and processing aids by weight, add them to a high-speed mixer, and mix for 5-8 minutes at a speed of 800-1000 r / min and a temperature of 80-90℃ to obtain a premix. High-speed mixing can initially disperse the components evenly, and the temperature can be used to slightly soften the resin, improving the adhesion of powder components such as flame retardants. Step 2, melt blending: The premixed material is added to a twin-screw extruder, and simultaneously, photoinitiator and crosslinking accelerator are added by weight through the side feed port. Melt blending and extrusion granulation are carried out under the conditions of 120-150℃ in each section of the extruder and a screw speed of 200-300 r / min to obtain initial granules. The shearing and mixing action of the twin-screw extruder can fully disperse the components. The addition of photoinitiator and crosslinking accelerator by the side feed port can prevent them from decomposing prematurely at high temperatures and ensure crosslinking activity. The specific temperature settings for each section of the twin-screw extruder are: feeding section 120-130℃, compression section 130-140℃, homogenization section 140-150℃, and die head temperature 145-150℃. Step 3: Drying and cooling. The initial particles are sent to a vibrating screen for screening to remove large particles and impurities. Then, they are sent to a cooling duct to be cooled to room temperature of 25-30℃. The cooled particles have good flowability and are easy to use in subsequent cable processing.

[0018] The aforementioned application of low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulation material involves extruding the insulation material around the conductor to form an insulation layer, which is then cross-linked by ultraviolet irradiation (irradiation dose 500-800mJ / cm², irradiation time 3-5s) to prepare 105℃ grade low-smoke halogen-free cross-linked insulated cables.

[0019] This invention optimizes the resin matrix ratio, selects a highly efficient photocrosslinking system and a composite flame-retardant system, and achieves long-term stable use of the material at 105℃, while also ensuring excellent mechanical properties, flame retardancy, processing fluidity, and weather resistance. This solves the problems of imbalance between crosslinking efficiency and performance, and the contradiction between processing and flame retardancy in existing materials. Through the synergistic ratio of EVA and POE and the three-dimensional network structure formed by ultraviolet irradiation crosslinking, the material exhibits excellent high-temperature resistance: a heat distortion temperature of 110-120℃, allowing for long-term stable use at 105℃. After a heat aging test (168h), the tensile strength retention rate is ≥85%, and the elongation at break retention rate is ≥80%, which is far superior to existing similar materials. The use of a compound photoinitiator and crosslinking accelerator system reduces the amount of photoinitiator (only 1.5-3 parts) while improving crosslinking efficiency, achieving a crosslinking degree of 70%-80%. Tensile strength is ≥12MPa, and elongation at break is ≥300%, meeting the mechanical performance requirements of cable insulation layers. The composite halogen-free flame-retardant system ensures an oxygen index ≥32% and vertical burning performance meets UL94 V-0. The material has a smoke density rating (SDR) ≤50, meeting the low-smoke, halogen-free environmental protection requirements. Furthermore, through optimization of processing aids and selection of the resin matrix, the melt flow index is 0.8-2.0 g / 10 min (190°C, 2.16 kg), exhibiting good extrusion flowability and a smooth insulation layer surface free of bubbles, impurities, and other defects. The combination of antioxidants and weathering agents effectively inhibits thermal oxidative degradation and photo-aging degradation. After a 1000-hour UV aging test, the material surface showed no cracking or powdering, the insulation resistance change rate was ≤15%, and the dielectric strength was ≥20 kV / mm, ensuring the safety and service life of the cable in complex environments. The material is halogen-free and releases no toxic gases during combustion, complying with RoHS, REACH, and other environmental standards. The preparation process is simple, and the UV irradiation crosslinking equipment requires low investment, consumes little energy, and has high production efficiency, making it suitable for large-scale industrial production and offering significant economic and social benefits.

[0020] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Detailed Implementation Example 1

[0021] The low-smoke, halogen-free, 105℃ UV-irradiated cross-linked insulating material, by weight, is mainly composed of 40 parts of ethylene-vinyl acetate copolymer (EVA, VA content 25%), 30 parts of polyolefin elastomer (POE, ethylene-octene copolymer, melt index 3g / 10min), 60 parts of magnesium hydroxide (particle size 3μm, silane modified), 30 parts of aluminum hydroxide (particle size 5μm), 2.25 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 0.75 parts of isopropylthioxanthone, 1 part of trimethylolpropane triacrylate (TMPTA), 0.4 parts of antioxidant 1010, 0.4 parts of antioxidant 168, 0.4 parts of UV absorber UV-326, 0.2 parts of hindered amine light stabilizer HALS770, 1 part of zinc stearate, and 1 part of polyethylene wax.

[0022] The preparation method of the low-smoke halogen-free 105℃ ultraviolet irradiation crosslinking grade insulation material involves premixing the above components (high-speed mixer speed 900 r / min, temperature 85°C, time 6 min), followed by melt blending (temperature of each section of twin-screw extruder: feeding section 125°C, compression section 135°C, homogenization section 145°C, die head temperature 148°C, screw speed 250 r / min), adding photoinitiator and TMPTA to the side feed, and then extruding, granulating, and cooling to room temperature to obtain the insulation material.

[0023] Performance testing: After the insulating material is extruded into an insulating layer, it is subjected to ultraviolet irradiation crosslinking (irradiation dose 650mJ / cm², irradiation time 4s). The test performance is as follows: heat distortion temperature 115°C, tensile strength retention rate 88% and elongation at break retention rate 83% after 168h of heat aging at 105°C, tensile strength 13.5MPa, elongation at break 320%, oxygen index 34%, vertical burning UL94 V-0 rating, smoke density rating 42, melt flow index 1.2g / 10min, insulation resistance change rate 12% and dielectric strength 22kV / mm after 1000h of ultraviolet aging. Example 2

[0024] This low-smoke, halogen-free, 105℃ UV-irradiated cross-linked insulating material, calculated by weight, mainly consists of the following components (parts by weight): 30 parts EVA (VA content 20%), 40 parts POE (ethylene-octene copolymer, melt index 1g / 10min), 50 parts magnesium hydroxide (particle size 1μm, silane modified), 25 parts aluminum hydroxide (particle size 2μm), 1.8 parts 2-hydroxy-2-methyl-1-phenyl-1-propanone, 0.6 parts isopropylthioxanthone, 0.5 parts PETA, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, 0.3 parts UV-326, 0.15 parts HALS 770, 0.5 parts zinc stearate, and 1 part polyethylene wax.

[0025] The preparation method of the low-smoke halogen-free 105℃ ultraviolet irradiation crosslinking grade insulation material involves premixing the above components (rotation speed 800 r / min, temperature 80°C, time 8 min), melt blending (extruder temperature: feeding section 120°C, compression section 130°C, homogenization section 140°C, die head temperature 145°C, screw speed 200 r / min), adding photoinitiator and PETA to the side feed, extruding and granulating, and cooling to room temperature to obtain the insulation material.

[0026] Performance testing: After UV irradiation crosslinking (dose 500mJ / cm², time 5s), the heat distortion temperature is 110°C. After heat aging at 105°C for 168h, the tensile strength retention rate is 85%, the elongation at break retention rate is 80%, the tensile strength is 12MPa, the elongation at break is 300%, the oxygen index is 32%, the vertical burning UL94 V-0 rating is 48, the smoke density rating is 48, the melt flow index is 0.8g / 10min, the insulation resistance change rate is 15% after UV aging for 1000h, and the dielectric strength is 20kV / mm. Example 3

[0027] This low-smoke, halogen-free, 105℃ UV-irradiated cross-linked insulating material, by weight, mainly consists of the following components (parts by weight): 50 parts EVA (VA content 30%), 20 parts POE (ethylene-octene copolymer, melt index 5g / 10min), 60 parts magnesium hydroxide (particle size 5μm, silane modified), 30 parts aluminum hydroxide (particle size 8μm), 2.4 parts 2-hydroxy-2-methyl-1-phenyl-1-propanone, 0.6 parts isopropylthioxanthone, 2 parts TMPTA, 0.5 parts antioxidant 1010, 0.5 parts antioxidant 168, 0.5 parts UV-326, 0.25 parts HALS 770, 1 part zinc stearate, and 2 parts polyethylene wax.

[0028] The preparation method of the low-smoke halogen-free 105℃ ultraviolet irradiation crosslinking grade insulation material involves premixing the above components (speed 1000 r / min, temperature 90°C, time 5 min), melt blending (extruder temperature: feeding section 130°C, compression section 140°C, homogenization section 150°C, die head temperature 150°C, screw speed 300 r / min), adding photoinitiator and TMPTA to the side feed, extruding and granulating, and cooling to room temperature to obtain the insulation material.

[0029] Performance testing: After UV irradiation crosslinking (dose 800mJ / cm², time 3s), the heat distortion temperature is 120°C. After heat aging at 105°C for 168h, the tensile strength retention rate is 90%, the elongation at break retention rate is 85%, the tensile strength is 15MPa, the elongation at break is 350%, the oxygen index is 36%, the vertical burning UL94 V-0 rating is 40, the smoke density rating is 40, the melt flow index is 2.0g / 10min, the insulation resistance change rate is 10% after UV aging for 1000h, and the dielectric strength is 25kV / mm.

[0030] Comparative Example 1: Compared with Example 1, POE was not added, the EVA dosage was adjusted to 70 parts, and other components and preparation methods were the same. Performance test results: after heat distortion temperature of 95°C and heat aging at 105°C for 168 hours, the tensile strength retention rate was 60%, the elongation at break retention rate was 55%, the tensile strength was 10 MPa, the elongation at break was 250%, the melt index was 0.5 g / 10 min, and the extruded surface was rough.

[0031] Comparative Example 2: Compared to Example 1, only 3 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone were used as the photoinitiator, and isopropylthioxanthone was not added. Other components and preparation methods were the same. Performance test results: crosslinking degree 55%, heat distortion temperature 100°C, tensile strength retention rate 70% and elongation at break retention rate 65% after heat aging at 105°C for 168 hours. The thick-walled insulation layer (thickness 2 mm) had insufficient internal crosslinking and poor breakdown resistance.

Claims

1. A low-smoke, halogen-free, 105℃ ultraviolet irradiation cross-linked insulating material, characterized in that: Based on weight, it is mainly composed of 20-60 parts of ethylene-vinyl acetate copolymer, 10-50 parts of polyolefin elastomer, 50-100 parts of halogen-free flame retardant, 1-4 parts of photoinitiator, 0.2-2.5 parts of crosslinking accelerator, 0.2-1.5 parts of antioxidant, 0.1-0.9 parts of weathering agent, and 0.5-3.5 parts of processing aid.

2. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claim 1, characterized in that: Based on weight, it is mainly composed of 30-50 parts of ethylene-vinyl acetate copolymer, 20-40 parts of polyolefin elastomer, 60-90 parts of halogen-free flame retardant, 1.5-3 parts of photoinitiator, 0.5-2 parts of crosslinking accelerator, 0.3-1 parts of antioxidant, 0.2-0.8 parts of weathering agent, and 1-3 parts of processing aid.

3. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claim 2, characterized in that: Based on weight, it is mainly composed of 40 parts of ethylene-vinyl acetate copolymer, 30 parts of polyolefin elastomer, 75 parts of halogen-free flame retardant, 3 parts of photoinitiator, 1 part of crosslinking accelerator, 1 part of antioxidant, 0.6 parts of weathering agent, and 2 parts of processing aid.

4. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claims 1-3, characterized in that: The halogen-free flame retardant, calculated by weight, is mainly composed of magnesium hydroxide and aluminum hydroxide in a weight ratio of 2:1-3:1; the polyolefin elastomer is an ethylene-octene copolymer with a melt index of 1-5 g / 10 min.

5. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claim 4, characterized in that: The photoinitiator, calculated by weight, is mainly composed of acetophenone-based and thioxanthone-based photoinitiators in a weight ratio of 3:1 to 4:

1.

6. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claim 5, characterized in that: The crosslinking accelerator is trimethylolpropane triacrylate or pentaerythritol triacrylate.

7. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claim 6, characterized in that: The antioxidants described herein, calculated by weight, are mainly composed of hindered phenolic antioxidants and phosphite antioxidants in a weight ratio of 1:

1.

8. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claim 7, characterized in that: The weathering agent, calculated by weight, mainly consists of an ultraviolet absorber and a hindered amine light stabilizer in a weight ratio of 2:

1.

9. The low-smoke halogen-free 105℃ ultraviolet irradiation cross-linked insulating material as described in claim 8, characterized in that: The processing aids, calculated by weight, are mainly composed of zinc stearate and polyethylene wax in a weight ratio of 1:1 to 1:

2.

10. A method for preparing a low-smoke, halogen-free, 105°C ultraviolet irradiation crosslinked insulating material as described in any one of claims 1-9, characterized in that: Includes the following steps: Step 1: Premixing. Weigh out the ethylene-vinyl acetate copolymer, polyolefin elastomer, halogen-free flame retardant, antioxidant, weathering agent and processing aid by weight, add them to a high-speed mixer, and mix for 5-8 minutes at a speed of 800-1000 r / min and a temperature of 80-90℃ to obtain the premix. Step 2, melt blending: The premixed material is added to a twin-screw extruder, and simultaneously, photoinitiator and crosslinking accelerator are added by weight through the side feed port. Melt blending and extrusion granulation are carried out under the conditions of 120-150℃ in each section of the extruder and 200-300 r / min of screw speed to obtain initial granules. The specific temperature settings for each section of the extruder are: feeding section 120-130℃, compression section 130-140℃, homogenization section 140-150℃, and die head temperature 145-150℃. Step 3: Drying and cooling. The initial particles are sent to a vibrating screen for screening to remove large particles and impurities. Then, they are sent to a cooling duct to cool to room temperature of 25-30℃ to obtain the final product.