Nuclear power cable insulation sleeve and its preparation process
The preparation of nuclear cable insulation sheaths by physical blending of composite flame retardants solves the problem of smoke and heat release from nuclear cables in fires, and improves the mechanical properties and fire safety of the insulation layer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI CABLE
- Filing Date
- 2026-06-05
- Publication Date
- 2026-07-21
AI Technical Summary
Existing nuclear power cable insulation materials release large amounts of smoke and heat during fires, exhibiting a high heat release rate as a fire hazard assessment indicator.
Cable insulation sheaths are prepared by physical blending of a combination of polyethylene, ethylene propylene rubber, silicone rubber, ethylene-vinyl acetate copolymer, composite flame retardant and radiation retardant. Attapulgite is used as a compound of zirconium phosphate and ammonium octamolate as a flame retardant material to enhance the mechanical properties of the insulation layer and reduce smoke and heat release.
It effectively reduces the release of smoke and heat from the cable insulation layer during a fire, improves the tensile strength and elongation at break of the insulation layer, and reduces the rate at which a fire damages the cable.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of cable manufacturing technology, specifically to the insulation sleeve of nuclear power cables and its manufacturing process. Background Technology
[0002] When cables burn, the heat release rate (HRR) is a key indicator for assessing fire hazard. Nuclear-grade cables require low-smoke, halogen-free flame-retardant insulation and sheathing materials, but they may still release toxic fumes during combustion. For example, PVC materials produce acidic gases and dioxins when burning, while XLPE, although halogen-free, may produce smoke and release heat due to incomplete decomposition during combustion. Furthermore, the total heat release increases with increasing heat radiation intensity, potentially exacerbating the spread of fire. Therefore, it is essential to develop a cable insulation sheath that effectively reduces the amount of smoke and heat generated by cables during a fire. Summary of the Invention
[0003] To address the shortcomings of existing technologies, this invention provides an insulating sleeve for nuclear power cables and its manufacturing process, which can effectively reduce the amount of smoke and heat generated by the cables during a fire.
[0004] To achieve the above objectives, the present invention provides the following technical solution: An insulating sleeve for nuclear power cables, the insulating sleeve being composed of the following raw materials in parts by weight: 30-40 parts polyethylene, 20-30 parts ethylene propylene rubber, 10-20 parts silicone rubber, 10-15 parts ethylene-vinyl acetate copolymer, 10-15 parts composite flame retardant, 3-5 parts radiation resistant, and 2-4 parts additives. The composite flame retardant is obtained by mixing attapulgite with zirconium phosphate and ammonium octamolate, wherein the ratio of zirconium phosphate to ammonium octamolate is <2.
[0005] Preferably, the mass ratio of attapulgite to zirconium phosphate is 3:1-2.
[0006] Preferably, the radiation-resistant agent is one of boron carbide, boron nitride, or high-phenyl silicone rubber.
[0007] Preferably, the additive is one of polyethylene wax or zinc stearate.
[0008] A method for preparing an insulating sleeve for a nuclear power cable is as follows: S1. Mix polyethylene, ethylene propylene rubber, silicone rubber, ethylene-vinyl acetate copolymer, and additives, melt them together, add composite flame retardant and radiation resist agent, mix them together, and extrude them to obtain molten material; S2. Immerse the molten material in cold water to cool it, then cut it into pellets to obtain flame-retardant pellets; S3. Re-mix the flame-retardant particles into agglomerates to obtain the composite material; S4. The composite material is melted and shaped on a two-roll mill, coated on the inner surface of the fiber, vulcanized, and irradiated to obtain a prefabricated insulating sleeve. S5. Cool the prefabricated insulating sleeve to room temperature to obtain the cable insulating sleeve.
[0009] Preferably, the mixing in step S3 is carried out at a furnace temperature of 170-190°C for 10-15 minutes in an internal mixer.
[0010] Preferably, the vulcanization in step S4 is carried out for 7-9 minutes on a vulcanizing machine at 170-180°C and 10-15 MPa.
[0011] Preferably, the irradiation energy for crosslinking in step S4 is 1-5 MeV, and the dose is 150-300 kGy.
[0012] Preferably, the cooling rate to room temperature in step S5 is 20-30℃ / h.
[0013] This invention provides an insulating sleeve for nuclear power cables and its manufacturing process, which has the following advantages compared to existing technologies: This invention utilizes attapulgite, zirconium phosphate, and ammonium octamolate as a flame-retardant material through physical blending. This not only enhances the tensile strength and elongation at break of the cable insulation layer but also effectively reduces the total amount of smoke released by the cable insulation layer in a fire, thus comprehensively improving the application value of the cable insulation layer proposed in this solution in fire accidents. Detailed Implementation
[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0015] Unless otherwise specified, all reagents used in the following schemes are commercially available products.
[0016] Preparation of composite flame retardants: Type A composite flame retardant: It is obtained by mixing attapulgite with zirconium phosphate and ammonium octamolate, wherein the mass ratio of attapulgite to zirconium phosphate and ammonium octamolate is 3:1:2. Type B composite flame retardant: It is obtained by mixing attapulgite with zirconium phosphate and ammonium octamolate, wherein the mass ratio of attapulgite to zirconium phosphate and ammonium octamolate is 3:1:0.3. Type C composite flame retardant: It is obtained by mixing attapulgite and zirconium phosphate, wherein the mass ratio of attapulgite to zirconium phosphate is 3:1; Type D composite flame retardant: It is obtained by mixing zirconium phosphate and ammonium octamolybdate, wherein the mass ratio of zirconium phosphate to ammonium octamolybdate is 1:2; Type E composite flame retardant: It is obtained by mixing attapulgite and ammonium octamolate, wherein the mass ratio of attapulgite to ammonium octamolate is 3:2. Example 1: The preparation steps of a method for manufacturing an insulating sleeve for a nuclear power cable are as follows: S1. Prepare the raw materials according to the following weight parts: 30 parts polyethylene, 20 parts ethylene propylene rubber, 10 parts silicone rubber, 10 parts ethylene-vinyl acetate copolymer, 10 parts type A composite flame retardant, 3 parts boron carbide, and 2 parts polyethylene wax. S2. Mix polyethylene, ethylene propylene rubber, silicone rubber, ethylene-vinyl acetate copolymer, and polyethylene wax, melt them together, add type A composite flame retardant and boron carbide, mix them together, and extrude them to obtain the melt material. S3. Immerse the molten material in cold water to cool it, then cut it into pellets to obtain flame-retardant pellets; S4. Mix the flame-retardant particles in a mixer at 180°C for 12 minutes to obtain the composite material. S5. The composite material is melted and shaped on a two-roll mill, coated on the inner surface of the fiber, vulcanized for 8 minutes at 175°C and 13MPa pressure in a vulcanizing machine, and irradiated at a speed of 4cm / s in an ion accelerator with an energy of 3MeV and a dose of 220kGy to obtain a prefabricated insulating sleeve. S6. Cool the prefabricated insulation sleeve to room temperature at a rate of 25℃ / h to obtain the cable insulation sleeve.
[0017] Example 2: This embodiment refers to the preparation method of Example 1, only the proportion of raw materials is different, specifically: S1. Prepare the raw materials according to the following weight parts: 40 parts polyethylene, 30 parts ethylene propylene rubber, 20 parts silicone rubber, 15 parts ethylene-vinyl acetate copolymer, 15 parts type A composite flame retardant, 5 parts boron nitride, and 4 parts zinc stearate. Comparative Example 1: This comparative example follows the preparation method of Example 2, except that the type A composite flame retardant is replaced with the type B composite flame retardant, and all other steps are the same. Comparative Example 2: This comparative example follows the preparation method of Example 2, except that the type A composite flame retardant is replaced with the type C composite flame retardant, and all other steps are the same. Comparative Example 3: This comparative example follows the preparation method of Example 2, except that the type A composite flame retardant is replaced with the type D composite flame retardant, and all other steps are the same. Comparative Example 4: This comparative example follows the preparation method of Example 2, except that the type A composite flame retardant is replaced with the type E composite flame retardant, and all other steps are the same. Comparative Example 5: This comparative example follows the preparation method of Example 2, except that steps S3 and S4 are deleted and step S5 is modified, specifically as follows: S5. Melt the molten material on a two-roll mill and form it into shape. Coat it onto the inner layer surface of the fiber and vulcanize it for 8 minutes on a vulcanizing machine at 175°C and 13MPa. Irradiate it at a speed of 4cm / s in an ion accelerator with an energy of 3MeV and a dose of 220kGy to obtain a prefabricated insulating sleeve. Detection: The samples prepared according to Examples 1-2 and Comparative Examples 1-5 were cut into 75×75×1mm pieces and used as test samples for the following tests: 1. Performance Testing According to GB-T 1040.3-2006 standard, the tensile strength (MPa) and elongation at break (%) of halogen-free low-smoke flame-retardant composite materials were determined using a universal mechanical testing machine. The tensile rate was 200 mm / min, and the average value was calculated after testing 5 pieces. The specific results are shown in Table 1. Table 1 As can be seen from the table above, the tensile strength and elongation at break of Example 2 are both good, that is, the addition of attapulgite, zirconium phosphate and ammonium octamolate can effectively improve the mechanical properties of the cable insulation layer.
[0018] 2. Flameless smoke density test In accordance with GB / T 8323.1-2008 standard, the maximum smoke emission (DS) and time to reach the maximum smoke emission (Time to Max) of the test sample were tested using an NBS smoke density test chamber, with a heat flux intensity of 25 KW / m². 2 The specific results are shown in Table 2: Table 2 As can be seen from the table above, the maximum smoke emission and the time of maximum smoke emission in Example 2 are both relatively small, which means that the combination of attapulgite, zirconium phosphate and ammonium octamolate in a mass ratio of 3:1:2 can effectively reduce the generation of smoke in the insulation layer during a fire.
[0019] 3. Cone calorimetry test According to ISO 5660-1 standard, cone calorimetry is used to determine the combustion characteristics of materials under a given heat flux intensity, effectively simulating real fire conditions. The cone calorimeter can measure data such as the total heat release rate (THR) and total smoke release rate (TSR) of materials, with a heat flux intensity of 50 kW / m³. 2 The specific results are shown in Table 3: Table 3 As shown in the table above, the total heat release rate and total smoke release of Example 2 are both relatively small, which can effectively suppress the flammability of the insulation layer and the amount of smoke generated, thereby reducing the rate of damage to the cable as a whole from the fire.
[0020] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. An insulating sleeve for a nuclear power cable, characterized in that, The insulating sleeve is composed of the following raw materials in parts by weight: 30-40 parts polyethylene, 20-30 parts ethylene propylene rubber, 10-20 parts silicone rubber, 10-15 parts ethylene-vinyl acetate copolymer, 10-15 parts composite flame retardant, 3-5 parts radiation resistant, and 2-4 parts additives. The composite flame retardant is obtained by mixing attapulgite with zirconium phosphate and ammonium octamolate, wherein the ratio of zirconium phosphate to ammonium octamolate is <2.
2. The nuclear power cable insulation sleeve according to claim 1, characterized in that, The mass ratio of attapulgite to zirconium phosphate is 3:1-2.
3. The nuclear power cable insulation sleeve according to claim 1, characterized in that, The radiation-resistant agent is specifically one of boron carbide, boron nitride, or high-phenyl silicone rubber.
4. The nuclear power cable insulation sleeve according to claim 1, characterized in that, The additive is specifically one of polyethylene wax or zinc stearate.
5. A method for preparing an insulating sleeve for a nuclear power cable as described in any one of claims 1-4, characterized in that, The specific preparation steps are as follows: S1. Mix polyethylene, ethylene propylene rubber, silicone rubber, ethylene-vinyl acetate copolymer, and additives, melt them together, add composite flame retardant and radiation resist agent, mix them together, and extrude them to obtain molten material; S2. Immerse the molten material in cold water to cool to room temperature, then cut into pellets to obtain flame-retardant pellets; S3. Re-mix the flame-retardant particles into agglomerates to obtain the composite material; S4. The composite material is melted and shaped on a two-roll mill, coated on the inner surface of the fiber, vulcanized, and irradiated to obtain a prefabricated insulating sleeve. S5. Cool the prefabricated insulating sleeve to room temperature to obtain the cable insulating sleeve.
6. The preparation method according to claim 5, characterized in that, The mixing in step S3 is carried out at a furnace temperature of 170-190℃ for 10-15 minutes in an internal mixer.
7. The preparation method according to claim 5, characterized in that, The vulcanization in step S4 is carried out for 7-9 minutes on a vulcanizing machine at 170-180℃ and 10-15MPa pressure.
8. The preparation method according to claim 5, characterized in that, The specific irradiation energy for the crosslinking in step S4 is 1-5 MeV, and the dose is 150-300 kGy.
9. The preparation method according to claim 5, characterized in that, The cooling rate to room temperature in step S5 is 20-30℃ / h.