Flame-retardant oil-resistant cable material and method for producing the same

Abstract

The application relates to the technical field of preparation of flame-retardant oil-resistant cable materials, and discloses a kind of flame-retardant oil-resistant cable materials and preparation method thereof.The method comprises the following steps: preparing an insulating base material, blending polyolefin base material, composite flame-retardant package and functional additives in a high-speed mixer at 90-100 DEG C to obtain the insulating base material; preparing a sheath base material, mixing and plasticizing elastomer base material, oil-resistant modified composition and stabilizer in an internal mixer at 125-135 DEG C to obtain the sheath base material; composite co-extrusion, the insulating base material is melt-coated on the conductor through a first extrusion system to form an insulating core wire, at the same time, the sheath base material is melt-coated through a second extrusion system to form a sheath layer on the outer periphery of the insulating core wire, and the product is obtained through cooling, setting, traction and winding.The method precisely controls the matching of components and the preparation parameters, combines the synchronous co-extrusion process, and makes the prepared cable material have excellent flame-retardant and oil-resistant synergistic performance and stable mechanical properties, the structure is closely combined, the preparation process is stable and reliable, and the method is suitable for cable preparation in harsh environments.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant and oil-resistant cable material preparation technology, specifically to a flame-retardant and oil-resistant cable material and its preparation method. Background Technology

[0002] As the core carrier of power transmission and signal transmission, cables are widely used in various fields such as industrial production, transportation, petrochemicals, and aerospace. In these application scenarios, cables often face complex and harsh environmental challenges, with flame risk and oil contamination being two of the most common destructive factors. In petrochemical workshops, ship engine rooms, and automobile engine compartments, cables not only need to have basic insulation and conductivity protection functions, but also must have excellent flame-retardant properties to prevent the rapid spread of flames in the event of a fire and avoid triggering a chain of safety accidents. At the same time, various oil contaminants such as mineral oil, lubricating oil, and fuel oil present in these environments can cause swelling and corrosion of the cable's outer materials. Long-term contact can lead to cracking, aging, and reduced strength of the cable sheath or insulation layer, thereby damaging the cable's insulation performance and causing faults such as leakage and short circuits, seriously threatening the normal operation of equipment and the safety of personnel.

[0003] To meet the requirements of the aforementioned special environments, flame-retardant and oil-resistant cable materials have become a key research and development focus in the industry. Currently, various cable materials with certain flame-retardant and oil-resistant properties have been developed, but they still have many shortcomings in practical applications. Regarding flame-retardant performance, some cable materials are modified with a single flame retardant, resulting in limited flame-retardant effects and difficulty in achieving high-level flame-retardant standards. Furthermore, when the amount of some flame retardants added is large, it leads to a significant decrease in the mechanical and processing properties of the material, affecting the cable's molding quality and service life. Regarding oil resistance, existing oil-resistant cable materials are mostly based on modifications of ordinary elastomers or polyolefins. The compatibility and stability of oil-resistant modification systems are poor, and after long-term immersion in oil, the volume change rate and performance degradation of the material are quite significant, failing to meet the requirements for long-term use in oily environments.

[0004] From a manufacturing process perspective, existing flame-retardant and oil-resistant cable materials are mostly prepared using a step-by-step mixing and secondary molding process. The matching of preparation parameters for the insulation base material and the sheath base material is poor. During the composite molding stage, problems such as weak bonding between the two layers and low interfacial peel strength easily occur, affecting the overall structural stability of the cable. Furthermore, in some manufacturing processes, parameters such as mixing temperature and extrusion temperature are not properly controlled, resulting in poor plasticization of the material and the presence of internal defects such as bubbles and impurities, further reducing the flame-retardant, oil-resistant, and mechanical strength of the cable material. Summary of the Invention

[0005] The purpose of this invention is to provide a flame-retardant and oil-resistant cable material and its preparation method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a flame-retardant and oil-resistant cable material and a method for preparing the same, the method comprising:

[0007] Preparation steps of insulating base material: Polyolefin base material, composite flame retardant package, and functional additives are blended in a high-temperature mixer at 90-100℃ to obtain insulating base material;

[0008] Preparation steps of sheath base material: The elastomer base material, oil-resistant modified composition and stabilizer are mixed and plasticized in an internal mixer at 125-135℃ to obtain the sheath base material;

[0009] Composite co-extrusion step: The insulating base material is melted in the first extrusion system and coated with the conductor to form an insulated core wire. At the same time, the sheath base material is melted in the second extrusion system and co-extruded on the outer periphery of the insulated core wire to form a sheath layer. After cooling, shaping and traction winding, the cable material is obtained.

[0010] Preferably, in the step of preparing the insulating base material, the composite flame retardant package includes a main flame retardant and a synergist, wherein the main flame retardant is magnesium hydroxide surface modified with a silane coupling agent, and the synergist is a compound of zinc borate and melamine cyanurate; in the insulating base material, by weight, the polyolefin base material is 100 parts, the composite flame retardant package is 40-60 parts, and the functional additives are 8-15 parts.

[0011] Preferably, in the step of preparing the insulating base material, the functional additives include anti-drip agent, processing aid, and color masterbatch, with a weight ratio of anti-drip agent: processing aid: color masterbatch = (3-5):(4-6):(1-2); the blending process adopts a three-stage feeding method, first adding the polyolefin base material and half of the processing aid, then adding the composite flame retardant package after heating to 80°C, and finally adding the remaining functional additives after heating to 95°C, with a total mixing time of 20-30 minutes.

[0012] Preferably, in the step of preparing the sheath base material, the oil-resistant modified composition comprises a polar polymer and a nano-reinforcing agent, wherein the polar polymer is a graft copolymer of chlorinated polyethylene and acrylate rubber, and the nano-reinforcing agent is modified montmorillonite; in the sheath base material, by weight, the elastomer base material is 100 parts, the oil-resistant modified composition is 25-40 parts, and the stabilizer is 3-5 parts.

[0013] Preferably, in the step of preparing the sheath base material, the mixing and plasticizing process is carried out in a pressure mixer with a filling coefficient of 0.7-0.75. The mixing process is as follows: first, add the elastomer base material and stabilizer, and mix at 120°C and 30 r / min for 2 minutes; then add the oil-resistant modified composition, raise the temperature to 130°C, increase the rotation speed to 45 r / min, and mix for 8-12 minutes until the torque is stable.

[0014] Preferably, in the compound co-extrusion step, the first extrusion system is a single-screw vented extruder, with its temperature settings from the feed port to the die head being 150℃, 165℃, 180℃, and 175℃ respectively, and the die head pressure being 8-12MPa; the second extrusion system is a twin-screw extruder, with its temperature settings from zone one to the die head being 140℃, 155℃, 170℃, 175℃, and 170℃ respectively.

[0015] Preferably, in the composite co-extrusion step, the cooling and shaping adopts a three-stage gradient cooling method. After the insulated core wire leaves the die head of the first extrusion system, it first passes through a 2-meter-long atomized water cooling chamber, with the water temperature controlled at 30-40℃. Subsequently, after co-extrusion with the sheath layer, it passes through a first-stage spray cooling water tank and a second-stage immersion cooling water tank in sequence, with the water temperatures controlled at 20-25℃ and 10-15℃, respectively.

[0016] The insulated core wire is cooled for 4-6 seconds in the atomized water cooling chamber, and the surface temperature of the wire body drops to 60-70℃. The co-extruded cable is cooled for 8-12 seconds in the first-stage spray cooling water tank and 15-20 seconds in the second-stage immersion cooling water tank, and the final temperature of the wire body after exiting the tank is below 40℃.

[0017] Preferably, after the composite co-extrusion step, a post-processing step is also included: the cable after traction and winding is heat-treated in an oven at 50-60°C for 4-8 hours, and then naturally cooled to room temperature; the traction and winding speed is 15-25m / min, and the winding tension is constantly controlled at 80-120N.

[0018] Preferably, after the steps of preparing the insulating base material and the sheath base material and before the composite co-extrusion step, the method further includes granulation and drying steps: the insulating base material is melt-extruded at 175-185°C using a parallel twin-screw extruder, water-cooled, granulated, and then hot-air dried at 70°C for 4 hours; the sheath base material is sheeted and granulated using an open mill, and then vacuum-dried at 60°C for 6 hours.

[0019] This invention also includes a flame-retardant and oil-resistant cable material, which is prepared using the above-described method for preparing a flame-retardant and oil-resistant cable material.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The method for preparing flame-retardant and oil-resistant cable materials provided by this invention, through precise design of the component matching and preparation process of the insulation base material and the sheath base material, combined with the synchronous composite co-extrusion molding method, significantly optimizes the flame-retardant performance, oil resistance, mechanical properties and structural stability of the resulting cable material, giving it many outstanding advantages.

[0022] In the preparation of the insulating base material, polyolefin base material is blended with composite flame-retardant packaging and functional additives within a specific temperature range. The polyolefin base material itself possesses excellent insulation properties and processing fluidity. The composite flame-retardant packaging employs a multi-component synergistic flame-retardant system, which enhances the flame-retardant performance of the insulating base material through the synergistic effect of different flame-retardant mechanisms. Compared to materials modified with a single flame retardant, it has a wider flame-retardant coverage, effectively inhibiting the ignition and spread of flames. The appropriate addition of functional additives improves the compatibility between the polyolefin base material and the composite flame-retardant packaging, preventing the flame retardant from agglomerating in the base material. It also optimizes the processing rheological properties of the insulating base material, ensuring smoothness in subsequent extrusion molding. Furthermore, the precise control of the blending temperature (90-100℃) ensures that all components are fully melted and mixed to form a uniform and stable mixture, while preventing degradation of the polyolefin base material due to excessively high temperatures, thus protecting the mechanical and insulation properties of the insulating base material.

[0023] The sheath base material is prepared using a combination system of elastomer base material, oil-resistant modified composition, and stabilizer. The elastomer base material possesses good elastic recovery and mechanical toughness, providing the cable with excellent impact resistance and bending performance, adapting to bending and stretching conditions during cable laying. The oil-resistant modified composition has good compatibility with the elastomer base material, forming a stable oil-resistant protective structure within the material, effectively preventing oil molecules from penetrating into the material, reducing the swelling and corrosive effects of oil, thereby extending the cable's service life in oily environments. The addition of stabilizer inhibits the oxidative aging reaction of the elastomer base material during processing and use, delaying the material's performance degradation and improving the long-term stability of the sheath base material. A mixing and plasticizing temperature of 125-135℃ ensures sufficient plasticization of the elastomer base material, while uniformly dispersing the oil-resistant modified composition and stabilizer in the base material, avoiding defects caused by insufficient plasticization, and ensuring the density and performance uniformity of the sheath base material.

[0024] In the composite molding stage, this invention employs a simultaneous co-extrusion method for the insulating base material and the sheath base material. Two independent extrusion systems are used to melt the insulating base material and the sheath base material separately. This allows for precise control of parameters such as melting temperature and extrusion rate based on the processing characteristics of the two base materials, ensuring that both materials possess matched flowability and plasticity in the molten state. During the overmolding process, the insulating base material tightly coats the conductor surface, forming a continuous and uniform insulated core, avoiding defects such as uneven insulation layer thickness and pinholes. Simultaneously, the sheath base material is simultaneously overmolded around the insulated core, forming a tight interfacial bond with it. This effectively improves the peel strength between the two layers, preventing interface separation during subsequent use and ensuring the overall structural stability of the cable. Furthermore, the simultaneous co-extrusion molding method reduces intermediate processing steps, shortens the production cycle, minimizes material performance loss due to multiple molding processes, and improves production efficiency and product qualification rate. Attached Figure Description

[0025] Figure 1 This diagram illustrates the working steps of a flame-retardant and oil-resistant cable material and its preparation method according to the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Any non-substantial modifications and adjustments made by those skilled in the art based on the present invention shall fall within the scope of protection of the present invention.

[0027] All raw materials used in this embodiment are commercially available conventional raw materials, including: linear low-density polyethylene (LLDPE, model 7042) as the polyolefin base material; ethylene propylene diene monomer (EPDM, model 4045) as the elastomer base material; magnesium hydroxide surface-modified with silane coupling agent (KH-550) with a particle size of 2-5 μm; zinc borate of industrial grade with a particle size of 1-3 μm; melamine cyanurate (MCA) of industrial grade; anti-dripping agent of polytetrafluoroethylene micro powder (PTFE, particle size 500 nm); processing aid of zinc stearate; masterbatch of black polyethylene; graft copolymer of chlorinated polyethylene and acrylate rubber (grafting rate 15%); modified montmorillonite of organo-montmorillonite (intercalating agent of hexadecyltrimethylammonium bromide); stabilizer of composite antioxidant (hindered phenolic antioxidant 1010 and phosphite antioxidant 168 compounded at a mass ratio of 1:1); and conductor of Φ1.5 mm copper conductor.

[0028] The performance testing method is as follows:

[0029] Flame retardant performance: Tested according to GB / T 18380.1-2008 "Cables and optical cables - Burning tests under flame conditions - Part 1: Vertical burning test of single insulated wires and cables", the judgment level is divided into FV-0, FV-1 and FV-2. If the FV-2 level is not reached, it is judged as unqualified.

[0030] Oil resistance performance: The oil resistance test was carried out according to Appendix A of GB / T 29510.12-2013 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables Part 12: General Test Methods for Thermal Aging Test". The sample was immersed in No. 10 machine oil at 100℃ for 168h, and the volume change rate and tensile strength retention rate before and after immersion were tested.

[0031] Mechanical properties: Tensile strength and elongation at break were tested according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets"; impact strength was tested according to GB / T 1843-2008 "Determination of impact strength of plastic cantilever beams".

[0032] Processing performance: The evaluation is based on the stability of the extrusion process, the uniformity of material plasticization, and the smoothness of the finished cable surface. The scoring standard is 1-5 points, with 5 points being the best (stable extrusion, uniform plasticization, and no surface defects) and 1 point being the worst (large extrusion fluctuations, poor plasticization, and uneven surface).

[0033] Example 1

[0034] refer to Figure 1 A method for preparing a flame-retardant and oil-resistant cable material, the specific steps of which are as follows:

[0035] 1. Raw material preparation: By weight, the insulation base material is: 100 parts of polyolefin base material (LLDPE 7042), 40 parts of composite flame retardant package (30 parts of magnesium hydroxide modified by KH-550, 6 parts of zinc borate, 4 parts of melamine cyanurate), and 8 parts of functional additives (3 parts of anti-dripping agent, 4 parts of processing aid, and 1 part of color masterbatch); the sheath base material is: 100 parts of elastomer base material (EPDM 4045), 25 parts of oil-resistant modified composition (20 parts of graft copolymer of chlorinated polyethylene and acrylate rubber, and 5 parts of modified montmorillonite), and 3 parts of stabilizer (1.5 parts of antioxidant 1010 + 1.5 parts of antioxidant 168).

[0036] 2. Preparation of insulating base material: Using a three-stage feeding method, the polyolefin base material and 2 parts of processing aid are added to a high-speed mixer, and the mixer is started at a speed of 300 r / min; when the temperature is raised to 80℃, the composite flame retardant package is added, and the mixing continues; when the temperature is raised to 95℃, the remaining 2 parts of processing aid, anti-dripping agent and color masterbatch are added, and the total mixing time is 20 minutes to obtain the insulating base material.

[0037] 3. Preparation of sheath base material: Add the elastomer base material and stabilizer to a pressure mixer with a filling coefficient of 0.7. Mix at 120℃ and 30r / min for 2 minutes. Then add the oil-resistant modified composition, heat to 130℃, increase the speed to 45r / min, and mix for 8 minutes until the torque is stable to obtain the sheath base material.

[0038] 4. Granulation and drying: The insulating base material is melt-extruded at 175°C using a parallel twin-screw extruder, water-cooled, pelletized, and then dried with hot air at 70°C for 4 hours; the sheath base material is sheeted and pelletized using an open mill, and then vacuum-dried at 60°C for 6 hours.

[0039] 5. Co-extrusion: The dried insulating base material is added to the first extrusion system (single-screw vented extruder), with the temperature settings from the feed port to the die head as follows: 150℃, 165℃, 180℃, 175℃, and the die head pressure controlled at 8MPa; the dried sheath base material is added to the second extrusion system (twin-screw extruder), with the temperature settings from zone one to the die head as follows: 140℃, 155℃, 170℃, 175℃, 170℃; the extruder is started, and the conductor is introduced into the die head of the first extrusion system. After the insulating base material melts, it coats the conductor to form an insulated core wire; the insulated core wire then enters the die head of the second extrusion system, and after the sheath base material melts, it is simultaneously co-extruded around the outer periphery of the insulated core wire to form a sheath layer (insulated core wire thickness 1.0mm, sheath layer thickness 1.5mm).

[0040] 6. Cooling and Shaping: After leaving the die head of the first extrusion system, the insulated core wire first passes through a 2-meter-long atomized water cooling chamber, with the water temperature controlled at 30℃ and a cooling time of 4 seconds, reducing the surface temperature of the wire to 70℃. Subsequently, the cable co-extruded with the sheath layer passes through the first-stage spray cooling water tank (water temperature 20℃, cooling time 8 seconds) and the second-stage immersion cooling water tank (water temperature 10℃, cooling time 15 seconds), with the final wire temperature exiting the tank at 35℃.

[0041] 7. Traction and winding: Pull the cable at a speed of 15m / min, keep the winding tension constant at 80N, and complete the winding.

[0042] 8. Post-processing: The cable after traction and winding is heat-treated in a drying room at 50°C for 4 hours, and then naturally cooled to room temperature to obtain flame-retardant and oil-resistant cable material.

[0043] Example 2

[0044] A method for preparing a flame-retardant and oil-resistant cable material, the specific steps of which are as follows:

[0045] 1. Raw material preparation: By weight, the insulating base material is: 100 parts of polyolefin base material (LLDPE 7042), 45 parts of composite flame retardant package (33 parts of magnesium hydroxide modified by KH-550, 8 parts of zinc borate, 4 parts of melamine cyanurate), and 10 parts of functional additives (3.5 parts of anti-dripping agent, 5 parts of processing aid, and 1.5 parts of color masterbatch); the sheath base material is: 100 parts of elastomer base material (EPDM4045), 30 parts of oil-resistant modified composition (24 parts of graft copolymer of chlorinated polyethylene and acrylate rubber, and 6 parts of modified montmorillonite), and 3.5 parts of stabilizer (1.75 parts of antioxidant 1010 + 1.75 parts of antioxidant 168).

[0046] 2. Preparation of insulating base material: Using a three-stage feeding method, the polyolefin base material and 2.5 parts of processing aids are added to a high-speed mixer, and the mixer is started at a speed of 350 r / min; when the temperature reaches 80℃, the composite flame retardant package is added, and the mixing continues; when the temperature reaches 95℃, the remaining 2.5 parts of processing aids, anti-dripping agent and color masterbatch are added, and the total mixing time is 25 minutes to obtain the insulating base material.

[0047] 3. Preparation of sheath base material: Add the elastomer base material and stabilizer to a pressure mixer with a filling coefficient of 0.72 and mix at 120℃ and 30r / min for 2 minutes; then add the oil-resistant modified composition, raise the temperature to 130℃, increase the speed to 45r / min, and mix for 10 minutes until the torque is stable to obtain the sheath base material.

[0048] 4. Granulation and drying: The insulating base material is melt-extruded at 180°C using a parallel twin-screw extruder, water-cooled, pelletized, and then dried with hot air at 70°C for 4 hours; the sheath base material is sheeted and pelletized using an open mill, and then vacuum-dried at 60°C for 6 hours.

[0049] 5. Co-extrusion: The dried insulating base material is added to the first extrusion system (single-screw vented extruder), with the temperature settings from the feed port to the die head as follows: 150℃, 165℃, 180℃, 175℃, and the die head pressure controlled at 10MPa; the dried sheathing base material is added to the second extrusion system (twin-screw extruder), with the temperature settings from zone one to the die head as follows: 140℃, 155℃, 170℃, 175℃, 170℃; the extruder is started, and the conductor is introduced into the die head of the first extrusion system. After the insulating base material melts, it coats the conductor to form an insulated core wire; the insulated core wire then enters the die head of the second extrusion system, and after the sheathing base material melts, it is simultaneously co-extruded around the outer periphery of the insulated core wire to form a sheath layer (insulated core wire thickness 1.0mm, sheath layer thickness 1.5mm).

[0050] 6. Cooling and Shaping: After leaving the die head of the first extrusion system, the insulated core wire first passes through a 2-meter-long atomized water cooling chamber, with the water temperature controlled at 35℃ and a cooling time of 5 seconds, reducing the surface temperature of the wire to 65℃. Subsequently, the cable co-extruded with the sheath layer passes through the first-stage spray cooling water tank (water temperature 22℃, cooling time 10 seconds) and the second-stage immersion cooling water tank (water temperature 12℃, cooling time 18 seconds), with the final wire temperature exiting the tank at 38℃.

[0051] 7. Traction and winding: Pull the cable at a speed of 20m / min, keep the winding tension constant at 100N, and complete the winding.

[0052] 8. Post-processing: The cable after traction and winding is heat-treated in a drying oven at 55°C for 6 hours, and then naturally cooled to room temperature to obtain flame-retardant and oil-resistant cable material.

[0053] Example 3

[0054] A method for preparing a flame-retardant and oil-resistant cable material, the specific steps of which are as follows:

[0055] 1. Raw material preparation: By weight, the insulating base material is: 100 parts of polyolefin base material (LLDPE 7042), 50 parts of composite flame retardant package (37 parts of magnesium hydroxide modified by KH-550, 8 parts of zinc borate, 5 parts of melamine cyanurate), and 12 parts of functional additives (4 parts of anti-dripping agent, 5.5 parts of processing aid, and 2.5 parts of color masterbatch); the sheath base material is: 100 parts of elastomer base material (EPDM4045), 35 parts of oil-resistant modified composition (28 parts of graft copolymer of chlorinated polyethylene and acrylate rubber, and 7 parts of modified montmorillonite), and 4 parts of stabilizer (2 parts of antioxidant 1010 + 2 parts of antioxidant 168).

[0056] 2. Preparation of insulating base material: Using a three-stage feeding method, the polyolefin base material and 2.75 parts of processing aids were added to a high-speed mixer, and the mixing was started at a speed of 320 r / min; when the temperature reached 80℃, the composite flame retardant package was added, and the mixing continued; when the temperature reached 95℃, the remaining 2.75 parts of processing aids, anti-dripping agent and color masterbatch were added, and the total mixing time was 28 minutes to obtain the insulating base material.

[0057] 3. Preparation of sheath base material: Add the elastomer base material and stabilizer to a pressure mixer with a filling coefficient of 0.73 and mix at 120℃ and 30r / min for 2 minutes; then add the oil-resistant modified composition, raise the temperature to 130℃, increase the speed to 45r / min, and mix for 11 minutes until the torque is stable to obtain the sheath base material.

[0058] 4. Granulation and drying: The insulating base material is melt-extruded at 182°C using a parallel twin-screw extruder, water-cooled, pelletized, and then dried with hot air at 70°C for 4 hours; the sheath base material is sheeted and pelletized using an open mill, and then vacuum-dried at 60°C for 6 hours.

[0059] 5. Co-extrusion: The dried insulating base material is added to the first extrusion system (single-screw vented extruder), with the temperature settings from the feed port to the die head as follows: 150℃, 165℃, 180℃, 175℃, and the die head pressure controlled at 11MPa; the dried sheathing base material is added to the second extrusion system (twin-screw extruder), with the temperature settings from zone one to the die head as follows: 140℃, 155℃, 170℃, 175℃, 170℃; the extruder is started, and the conductor is introduced into the die head of the first extrusion system. After the insulating base material melts, it coats the conductor to form an insulated core wire; the insulated core wire then enters the die head of the second extrusion system, and after the sheathing base material melts, it is simultaneously co-extruded around the outer periphery of the insulated core wire to form a sheath layer (insulated core wire thickness 1.0mm, sheath layer thickness 1.5mm).

[0060] 6. Cooling and Shaping: After leaving the die head of the first extrusion system, the insulated core wire first passes through a 2-meter-long atomized water cooling chamber, with the water temperature controlled at 38℃ and a cooling time of 5.5 seconds, reducing the surface temperature of the wire to 62℃. Subsequently, the cable co-extruded with the sheath layer passes through the first-stage spray cooling water tank (water temperature 24℃, cooling time 11 seconds) and the second-stage immersion cooling water tank (water temperature 14℃, cooling time 19 seconds), with the final wire temperature exiting the tank at 39℃.

[0061] 7. Traction and winding: Pull the cable at a speed of 23m / min, keep the winding tension constant at 110N, and complete the winding.

[0062] 8. Post-processing: The cable after traction and winding is heat-treated in a drying oven at 58°C for 7 hours, and then naturally cooled to room temperature to obtain flame-retardant and oil-resistant cable material.

[0063] Example 4

[0064] A method for preparing a flame-retardant and oil-resistant cable material, the specific steps of which are as follows:

[0065] 1. Raw material preparation: By weight, the insulation base material is: 100 parts of polyolefin base material (LLDPE 7042), 55 parts of composite flame retardant packaging (40 parts of magnesium hydroxide modified with KH-550, 9 parts of zinc borate, 6 parts of melamine cyanurate), and 14 parts of functional additives (4.5 parts of anti-dripping agent, 5.8 parts of processing aid, and 3.7 parts of color masterbatch); the sheath base material is: 100 parts of elastomer base material (EPDM4045), 38 parts of oil-resistant modified composition (30 parts of graft copolymer of chlorinated polyethylene and acrylate rubber, and 8 parts of modified montmorillonite), and 4.5 parts of stabilizer (2.25 parts of antioxidant 1010 + 2.25 parts of antioxidant 168).

[0066] 2. Preparation of insulating base material: Using a three-stage feeding method, the polyolefin base material and 2.9 parts of processing aids were added to a high-speed mixer, and the mixing was started at a speed of 360 r / min; when the temperature reached 80℃, the composite flame retardant package was added, and the mixing continued; when the temperature reached 95℃, the remaining 2.9 parts of processing aids, anti-dripping agent and color masterbatch were added, and the total mixing time was 29 minutes to obtain the insulating base material.

[0067] 3. Preparation of sheath base material: Add the elastomer base material and stabilizer to a pressure mixer with a filling coefficient of 0.74 and mix at 120℃ and 30r / min for 2 minutes; then add the oil-resistant modified composition, raise the temperature to 130℃, increase the speed to 45r / min, and mix for 11.5 minutes until the torque is stable to obtain the sheath base material.

[0068] 4. Granulation and drying: The insulating base material is melt-extruded at 183°C using a parallel twin-screw extruder, water-cooled, pelletized, and then dried with hot air at 70°C for 4 hours; the sheath base material is sheeted and pelletized using an open mill, and then vacuum-dried at 60°C for 6 hours.

[0069] 5. Co-extrusion: The dried insulating base material is added to the first extrusion system (single-screw vented extruder), with the temperature settings from the feed port to the die head as follows: 150℃, 165℃, 180℃, 175℃, and the die head pressure controlled at 11.5MPa. The dried sheathing base material is added to the second extrusion system (twin-screw extruder), with the temperature settings from zone one to the die head as follows: 140℃, 155℃, 170℃, 175℃, 170℃. The extruder is started, and the conductor is introduced into the die head of the first extrusion system. After the insulating base material melts, it coats the conductor to form an insulated core wire. The insulated core wire then enters the die head of the second extrusion system, where the sheathing base material melts and is simultaneously co-extruded around the outer periphery of the insulated core wire to form a sheath layer (insulated core wire thickness 1.0mm, sheath layer thickness 1.5mm).

[0070] 6. Cooling and Shaping: After leaving the die head of the first extrusion system, the insulated core wire first passes through a 2-meter-long atomized water cooling chamber, with the water temperature controlled at 39℃ and a cooling time of 5.8 seconds, reducing the surface temperature of the wire to 61℃. Subsequently, the cable co-extruded with the sheath layer passes through the first-stage spray cooling water tank (water temperature 24.5℃, cooling time 11.5 seconds) and the second-stage immersion cooling water tank (water temperature 14.5℃, cooling time 19.5 seconds), with the final wire temperature exiting the tank at 39.5℃.

[0071] 7. Traction and winding: Pull the cable at a speed of 24m / min, keep the winding tension constant at 115N, and complete the winding.

[0072] 8. Post-processing: The cable after traction and winding is heat-treated in a drying oven at 59°C for 7.5 hours, and then naturally cooled to room temperature to obtain flame-retardant and oil-resistant cable material.

[0073] Example 5

[0074] A method for preparing a flame-retardant and oil-resistant cable material, the specific steps of which are as follows:

[0075] 1. Raw material preparation: By weight, the insulation base material is: 100 parts of polyolefin base material (LLDPE 7042), 60 parts of composite flame retardant package (45 parts of magnesium hydroxide modified by KH-550, 10 parts of zinc borate, 5 parts of melamine cyanurate), and 15 parts of functional additives (5 parts of anti-dripping agent, 6 parts of processing aid, and 4 parts of color masterbatch); the sheath base material is: 100 parts of elastomer base material (EPDM 4045), 40 parts of oil-resistant modified composition (32 parts of graft copolymer of chlorinated polyethylene and acrylate rubber, and 8 parts of modified montmorillonite), and 5 parts of stabilizer (2.5 parts of antioxidant 1010 + 2.5 parts of antioxidant 168).

[0076] 2. Preparation of insulating base material: Using a three-stage feeding method, the polyolefin base material and 3 parts of processing aids are added to a high-speed mixer, and the mixing is started at a speed of 380 r / min; when the temperature is raised to 80℃, the composite flame retardant package is added, and the mixing continues; when the temperature is raised to 95℃, the remaining 3 parts of processing aids, anti-dripping agent and color masterbatch are added, and the total mixing time is 30 minutes to obtain the insulating base material.

[0077] 3. Preparation of sheath base material: Add the elastomer base material and stabilizer to a pressure mixer with a filling coefficient of 0.75 and mix at 120℃ and 30r / min for 2 minutes; then add the oil-resistant modified composition, raise the temperature to 130℃, increase the speed to 45r / min, and mix for 12 minutes until the torque is stable to obtain the sheath base material.

[0078] 4. Granulation and drying: The insulating base material is melt-extruded at 185°C using a parallel twin-screw extruder, water-cooled, pelletized, and then dried with hot air at 70°C for 4 hours; the sheath base material is sheeted and pelletized using an open mill, and then vacuum-dried at 60°C for 6 hours.

[0079] 5. Co-extrusion: The dried insulating base material is added to the first extrusion system (single-screw vented extruder), with the temperature settings from the feed port to the die head as follows: 150℃, 165℃, 180℃, 175℃, and the die head pressure controlled at 12MPa; the dried sheath base material is added to the second extrusion system (twin-screw extruder), with the temperature settings from zone one to the die head as follows: 140℃, 155℃, 170℃, 175℃, 170℃; the extruder is started, and the conductor is introduced into the die head of the first extrusion system. After the insulating base material melts, it coats the conductor to form an insulated core wire; the insulated core wire then enters the die head of the second extrusion system, and after the sheath base material melts, it is simultaneously co-extruded around the outer periphery of the insulated core wire to form a sheath layer (insulated core wire thickness 1.0mm, sheath layer thickness 1.5mm).

[0080] 6. Cooling and Shaping: After leaving the die head of the first extrusion system, the insulated core wire first passes through a 2-meter-long atomized water cooling chamber, with the water temperature controlled at 40℃ and a cooling time of 6 seconds, reducing the surface temperature of the wire to 60℃. Subsequently, the cable co-extruded with the sheath layer passes through the first-stage spray cooling water tank (water temperature 25℃, cooling time 12 seconds) and the second-stage immersion cooling water tank (water temperature 15℃, cooling time 20 seconds), finally exiting the tank at a wire temperature of 40℃.

[0081] 7. Traction and winding: Pull the cable at a speed of 25m / min, keep the winding tension constant at 120N, and complete the winding.

[0082] 8. Post-processing: The cable after traction and winding is heat-treated in a drying room at 60°C for 8 hours, and then naturally cooled to room temperature to obtain flame-retardant and oil-resistant cable material.

[0083] Comparative Example 1

[0084] A method for preparing a cable material is basically the same as that in Example 3, except that: when preparing the insulating base material, no synergist (zinc borate and melamine cyanurate) is added to the composite flame retardant package, and only 50 parts of magnesium hydroxide modified by KH-550 are added. The remaining raw materials, dosages, and process parameters are the same as in Example 3.

[0085] Comparative Example 2

[0086] A method for preparing a cable material is basically the same as that in Example 3, except that: when preparing the sheath base material, no oil-resistant modified composition is added, and the other raw materials, dosages, and process parameters are the same as in Example 3.

[0087] Comparative Example 3

[0088] A method for preparing a cable material is basically the same as that in Example 3, except that: in the cooling and shaping step, a three-stage gradient cooling is not used, but only a single-stage immersion cooling water tank (water temperature 20°C) is set up, with a cooling time of 30 seconds. The remaining raw materials, dosages, and process parameters are the same as in Example 3.

[0089] Table 1: Raw Material Formulation Table for Examples and Comparative Examples

[0090]

[0091]

[0092] Within the scope of this invention, the formulations of Examples 1-5 were used to create a series of implementation schemes by gradually adjusting the amounts of the composite flame-retardant pack (40-60 parts), the oil-resistant modified composition (25-40 parts), and the functional additives (8-15 parts) to explore the influence of different raw material ratios on the performance of cable materials. Comparative Example 1, by removing the synergistic agents (zinc borate and melamine cyanurate) from the composite flame-retardant pack and retaining only the main flame retardant, was used to verify the synergistic effect of the synergistic agents in the flame-retardant system. Comparative Example 2 removed the oil-resistant modified composition to verify the key role of this composition in the oil resistance of the material. Comparative Example 3 had a formulation completely identical to Example 3, except for the cooling process, to verify the necessity of the three-stage gradient cooling process. Each comparative example was designed with a clear comparative focus, accurately highlighting the superiority of the technical features of this invention.

[0093] Table 2: Performance Test Results of Examples and Comparative Examples

[0094]

[0095] Examples 1-5 all exhibited excellent flame-retardant performance, with Example 1 achieving an FV-1 rating and Examples 2-5 reaching an FV-0 rating. This indicates that the flame-retardant performance gradually improves with increasing amounts of the composite flame-retardant pack. This is because the main flame retardant (modified magnesium hydroxide) in the composite flame-retardant pack decomposes and absorbs heat at high temperatures, releasing water vapor, which cools and dilutes oxygen. The synergists zinc borate and melamine cyanurate work synergistically with the main flame retardant. Zinc borate promotes char formation, and the non-combustible gases released from the decomposition of melamine cyanurate further isolate oxygen. Together, these three components construct a highly efficient flame-retardant system. In contrast, Comparative Example 1, lacking synergists and relying solely on the main flame retardant, failed to form a dense flame-retardant char layer, and its flame-retardant rating did not meet the qualification standard. This fully demonstrates the indispensability of synergists in flame-retardant systems.

[0096] In Examples 1-5, the oil resistance volume change rate was controlled between +1.8% and +3.2%, and the oil resistance tensile strength retention rate was higher than 85%. Furthermore, the oil resistance performance gradually improved with increasing dosage of the oil-resistant modified composition. This is because the chlorinated polyethylene-acrylate rubber graft copolymer in the oil-resistant modified composition has strong polarity, which can repel the non-polar components in the engine oil. Simultaneously, the layered structure of the modified montmorillonite can hinder the penetration of engine oil molecules. Both factors synergistically enhance the oil resistance performance of the material. In Comparative Example 2, without the addition of the oil-resistant modified composition, the oil resistance volume change rate was as high as +8.5%, and the tensile strength retention rate was only 62.3%, indicating a severe deterioration in oil resistance performance. This highlights the crucial role of the oil-resistant modified composition in improving the oil resistance performance of the material.

[0097] The tensile strength of Examples 1-5 ranged from 12.5 to 15.3 MPa, the elongation at break ranged from 385% to 438%, and the impact strength ranged from 28.5 to 34.2 kJ / m². The overall mechanical properties were excellent and gradually improved with optimized raw material proportions. This was due to the good compatibility of the components: the magnesium hydroxide modified with the silane coupling agent had a strong interfacial bond with the polyolefin base material, reducing the loss of mechanical properties; the modified montmorillonite in the oil-resistant modified composition acted as a reinforcement, improving the tensile strength and impact strength of the material. Comparative Example 1 had slightly lower mechanical properties than Example 3 due to an imperfect flame-retardant system; Comparative Example 2 had poor mechanical properties due to the lack of reinforcement from the oil-resistant modified composition; Comparative Example 3 had significantly reduced tensile strength, elongation at break, and impact strength to only 11.8 MPa, 325%, and 24.5 kJ / m², respectively, due to an unreasonable cooling process that caused stress concentration within the material.

[0098] The processing performance scores of Examples 1-5 were all 4 points or higher, with Examples 3-5 reaching 5 points, indicating that the formula and process of the present invention have good processing adaptability. The three-stage feeding method ensures uniform mixing of the components of the insulating base material, the specific process parameters of the pressure mixer ensure sufficient plasticization of the sheath base material, the temperature setting of the composite co-extrusion ensures stable molten state of the material, and the three-stage gradient cooling avoids defects such as shrinkage cavities and cracks on the cable surface. Comparative Example 3, due to the use of single-stage cooling, had an excessively fast cooling rate, resulting in a large temperature difference between the cable surface and interior, generating stress, leading to a decrease in surface smoothness, and a processing performance score of only 3 points.

[0099] Table 3: Comparison of the impact of different cooling processes on cable performance

[0100]

[0101] Table 3 compares the effects of different cooling processes on cable performance. The control group, based on Example 3, retains only atomized water cooling and the first-stage spray cooling in the cooling and shaping steps, omitting the second-stage immersion cooling. The data shows that the three-stage gradient cooling process used in Example 3 is the most effective: the insulated core wire is first rapidly cooled to 62°C by atomized water cooling, preventing oxidation and aging of the insulation layer due to prolonged high-temperature exposure; subsequently, the co-extruded sheath layer undergoes two-stage gradient cooling (24°C spray → 14°C immersion), allowing the cable temperature to steadily drop to 39°C, effectively reducing internal stress. Therefore, the cable surface is smooth and flawless, with optimal mechanical and processing performance. The first-stage cooling process in Comparative Example 3, due to its excessively rapid cooling rate, caused a sharp increase in the temperature difference between the cable surface and interior, resulting in microcracks on the surface and stress concentration inside, significantly reducing mechanical performance and achieving the lowest processing performance score. The control group, lacking the second-stage deep cooling, could not reduce the final cable temperature to a reasonable range, resulting in residual internal stress and localized shrinkage cavities on the surface. Its mechanical and processing performance falls between that of Example 3 and Comparative Example 3. This fully demonstrates that the three-stage gradient cooling process used in this invention can significantly improve the surface quality and mechanical properties of cables, and is one of the key processes to ensure product quality.

[0102] This invention, through the rational design of the insulation and sheathing base material formulations and the adoption of specific processes such as three-stage feeding and blending, pressurized internal mixing and plasticizing, composite co-extrusion, and three-stage gradient cooling, successfully prepared cable materials with excellent flame retardant properties, oil resistance, mechanical properties, and processing performance. Examples 3-5 exhibit the best overall performance, with Example 3 showing the optimal formulation and process parameters: 50 parts of a composite flame retardant package (37 parts modified magnesium hydroxide + 8 parts zinc borate + 5 parts melamine cyanurate), 35 parts of an oil-resistant modified composition (28 parts graft copolymer + 7 parts modified montmorillonite), and a three-stage gradient cooling and 58℃×7-hour post-treatment process. The resulting cable material achieved an FV-0 flame retardant rating, an oil resistance volume change rate of only +2.1%, a tensile strength of 14.8 MPa, an elongation at break of 425%, and excellent processing performance.

[0103] Comparative test results show that the synergist in the composite flame-retardant package, the oil-resistant modified composition in the sheath base material, and the three-stage gradient cooling process are the key technical features for achieving the technical effects of this invention. The absence of any one of these features will lead to a significant deterioration of one or more properties of the cable material. The preparation method of this invention is stable, highly operable, and suitable for industrial production. The prepared flame-retardant and oil-resistant cable material can be widely used in petrochemical, shipbuilding, mining, and other fields with high requirements for cable flame retardancy and oil resistance.

[0104] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a flame-retardant and oil-resistant cable material, characterized in that, include: Preparation steps of insulating base material: Polyolefin base material, composite flame retardant package, and functional additives are blended in a high-temperature mixer at 90-100℃ to obtain insulating base material; Preparation steps of sheath base material: The elastomer base material, oil-resistant modified composition and stabilizer are mixed and plasticized in an internal mixer at 125-135℃ to obtain the sheath base material; Composite co-extrusion step: The insulating base material is melted through the first extrusion system and coated with the conductor to form an insulated core wire. At the same time, the sheath base material is melted through the second extrusion system and co-extruded on the outer periphery of the insulated core wire to form a sheath layer. After cooling, shaping and traction winding, the cable material is obtained. The mixing and plasticizing process is carried out in a pressure internal mixer with a mixing chamber filling coefficient of 0.7-0.

75. The mixing process is as follows: first, add the elastomer base material and stabilizer, and mix at 120°C and 30 r / min for 2 minutes; then add the oil-resistant modified composition, raise the temperature to 130°C, increase the speed to 45 r / min, and mix for 8-12 minutes until the torque is stable. The cooling and shaping process adopts a three-stage gradient cooling method. After the insulated core wire leaves the die head of the first extrusion system, it first passes through a 2-meter-long atomized water cooling chamber, where the water temperature is controlled at 30-40℃. Then, after co-extrusion with the sheath layer, it passes through the first-stage spray cooling water tank and the second-stage immersion cooling water tank in sequence, where the water temperature is controlled at 20-25℃ and 10-15℃, respectively. The insulated core wire is cooled for 4-6 seconds in the atomized water cooling chamber, and the surface temperature of the wire body drops to 60-70℃; the co-extruded cable is cooled for 8-12 seconds in the first-stage spray cooling water tank and 15-20 seconds in the second-stage immersion cooling water tank, and the final temperature of the wire body after exiting the tank is below 40℃. In the step of preparing the insulating base material, the composite flame retardant package contains a main flame retardant and a synergist. The main flame retardant is magnesium hydroxide surface-modified with a silane coupling agent, and the synergist is a compound of zinc borate and melamine cyanurate. In the insulating base material, by weight, the polyolefin base material is 100 parts, the composite flame retardant package is 40-60 parts, and the functional additives are 8-15 parts. In the step of preparing the insulating base material, the functional additives include anti-drip agent, processing aid and color masterbatch, with a weight ratio of anti-drip agent: processing aid: color masterbatch = (3-5):(4-6):(1-2); the blending process adopts a three-stage feeding method, first adding the polyolefin base material and half of the processing aid, then adding the composite flame retardant package after heating to 80°C, and finally adding the remaining functional additives after heating to 95°C, with a total mixing time of 20-30 minutes; In the step of preparing the sheath base material, the oil-resistant modified composition comprises a polar polymer and a nano-reinforcing agent. The polar polymer is a graft copolymer of chlorinated polyethylene and acrylate rubber, and the nano-reinforcing agent is modified montmorillonite. In the sheath base material, by weight, the elastomer base material is 100 parts, the oil-resistant modified composition is 25-40 parts, and the stabilizer is 3-5 parts.

2. The method for preparing a flame-retardant and oil-resistant cable material according to claim 1, characterized in that, In the compound co-extrusion step, the first extrusion system is a single-screw vented extruder, with its temperature settings from the feed port to the die head being 150℃, 165℃, 180℃, and 175℃ respectively, and the die head pressure being 8-12MPa; the second extrusion system is a twin-screw extruder, with its temperature settings from zone one to the die head being 140℃, 155℃, 170℃, 175℃, and 170℃ respectively.

3. The method for preparing a flame-retardant and oil-resistant cable material according to claim 1, characterized in that, Following the co-extrusion step, a post-processing step is also included: the cable after traction and winding is heat-treated in an oven at 50-60℃ for 4-8 hours, and then naturally cooled to room temperature; the traction and winding speed is 15-25m / min, and the winding tension is constantly controlled at 80-120N.

4. The method for preparing a flame-retardant and oil-resistant cable material according to claim 1, characterized in that, After the steps of preparing the insulating base material and the sheath base material and before the composite co-extrusion step, granulation and drying steps are also included respectively: the insulating base material is melt-extruded at 175-185℃ using a parallel twin-screw extruder, water-cooled, granulated, and hot-air dried at 70℃ for 4 hours; the sheath base material is sheeted and granulated using an open mill, and vacuum dried at 60℃ for 6 hours.

5. A flame-retardant and oil-resistant cable material, characterized in that, It is prepared by the method of any one of claims 1-4 for preparing a flame-retardant and oil-resistant cable material.

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