A fire-resistant cross-linked polyethylene for cable sheathing and its production process

Abstract

This invention relates to the field of materials technology and discloses a fire-resistant cross-linked polyethylene for cable sheathing and its production process. The cross-linked polyethylene is made by first melt cross-linking polymerization of high-density polyethylene as the main raw material, and then by blending and extrusion of a compatibilizer, aluminosilicate fiber modifier, and nitrile rubber auxiliary material. The aluminosilicate fiber modifier is a surface-modified reactive polymer flame retardant aluminosilicate fiber. The presence of the polymer flame retardant is equivalent to creating a "transition" layer between the aluminosilicate fiber and the high-density polyethylene matrix, which is beneficial to improving the interfacial bonding between the aluminosilicate fiber and the high-density polyethylene, thereby allowing the aluminosilicate fiber to fully exert its reinforcing and modifying effect as an inorganic fiber. The polymer flame retardant contains a large amount of phosphorus and silicon flame retardant elements, which can effectively improve the flame retardant and fire-resistant properties of cross-linked polyethylene.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a fire-resistant cross-linked polyethylene for cable sheathing and its production process. Background Technology

[0002] Cables are a crucial component of power and communication systems, and the cable sheath plays a vital role in protecting the internal structure of the cable, enhancing its mechanical strength, and improving its corrosion resistance. Currently, cables generally consist of a conductor, an insulation layer, a separator, and an outer sheath. The insulation layer is typically formed by coating the conductor with minerals such as mica, providing good explosion-proof properties. The separator is usually made of aluminum, and the outer sheath is commonly made of polymer materials such as polyethylene. However, in certain specialized industries, such as the petrochemical industry, cables need to withstand long-term corrosion from petroleum and chemical media. This requires cable sheath materials with superior corrosion resistance. Polyethylene sheath materials generally have low oil and corrosion resistance, failing to meet these requirements and hindering the safe and reliable operation of cables in harsh environments. Compared to conventional polyethylene, cross-linked polyethylene (XLPE) offers superior heat resistance, mechanical strength, and chemical resistance, while also possessing good insulation properties, thus meeting the demands of harsher operating environments.

[0003] Furthermore, fire resistance is one of the important performance indicators of cable sheaths, which is of great significance for ensuring the safe and stable operation of power systems. However, although cross-linked polyethylene (XLPE) has relatively excellent overall performance, it is a flammable material that is extremely prone to combustion and will also be accompanied by melting and dripping, causing the fire to spread, thus posing a significant safety hazard. At present, the flame retardant and fire-resistant properties of XLPE are generally improved by adding flame retardants, such as inorganic flame retardants like magnesium hydroxide and aluminum hydroxide, and organophosphorus flame retardants like DOPO. However, the effect of inorganic flame retardants is relatively insignificant, and large amounts are needed to achieve a certain effect, which will impact the mechanical properties of polymer materials. Although organophosphorus flame retardants such as DOPO have good flame-retardant modification effects, they are prone to volatility and migration, making it difficult to guarantee the long-term flame-retardant effect of the material. Based on this, the present invention provides an insulating and fire-resistant XLPE with excellent flame-retardant and fire-resistant properties, which can be directly used to manufacture cable sheaths. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a fire-resistant cross-linked polyethylene for cable sheathing and its production process.

[0006] (II) Technical Solution

[0007] A manufacturing process for fire-resistant cross-linked polyethylene for cable sheathing, wherein the cross-linked polyethylene is made from the following raw materials in parts by weight:

[0008]

[0009] The production process includes the following steps:

[0010] Step 1: Weigh all the ingredients according to the specified weight proportions and let them stand for later use;

[0011] The second step involves adding high-density polyethylene, nitrile rubber, and initiator into a torque rheometer, controlling the temperature at 180-190℃ and the rotation speed at 50-60 rpm, and then stopping the heating after 5-10 minutes of melt crosslinking polymerization, cooling down, and discharging the material to form a polymer.

[0012] The third step involves adding the polymer material, compatibilizer, aluminum silicate fiber modifier, antioxidant, inorganic filler, and lubricant to a mixer. After mechanically mixing the mixture at 80-100℃, the mixture is fed into an extruder. The temperatures of each zone are controlled sequentially as follows: 190±5℃, 200±5℃, 210±5℃, 210±5℃, 220±5℃, and 210±5℃. The screw speed is controlled at 100-150 r / min. After melt extrusion, cross-linked polyethylene can be obtained.

[0013] As a further aspect of the present invention, the compatibilizer is maleic anhydride-grafted polyethylene or maleic anhydride-grafted polypropylene.

[0014] As a further aspect of the present invention, the specific preparation method of the aluminum silicate fiber modified additive is as follows:

[0015] Aluminosilicate fibers are added to a 1,4-dioxane solvent and ultrasonically treated at an ultrasonic frequency of 80-100 kHz for 20-40 minutes. Then, a reactive polymer flame retardant is added. After the addition is complete, the mixture is stirred evenly and protected with nitrogen gas. The temperature is then gradually increased to 70-80℃ at a heating rate of 2-3℃ / min and kept at this temperature for 6-9 hours. The nitrogen gas is then removed, heating is stopped, and the material is collected by centrifugation. After washing and vacuum drying, the aluminosilicate fiber modified additive can be obtained.

[0016] As a further aspect of the present invention, the specific preparation method of the reactive polymeric flame retardant includes the following steps:

[0017] Step S1: Add the reactive phosphorus-containing flame retardant and glycidol to toluene. After the addition is complete, start stirring and wait for a homogeneous reaction solution to form. Then, purge with nitrogen for protection, start heating, and maintain the temperature at 90-100℃. After stirring for 6-8 hours, stop heating, cool down and discharge the material, collect the product, and obtain the ligation reagent.

[0018] Step S2: Mix the connecting reagent, bibenzyloxydichlorosilane and tetrahydrofuran, stir until uniform, raise the temperature to 60-65℃, maintain this temperature for 4-6 hours, then add the acid-binding agent to the mixture. After the addition is complete, continue to keep warm and stir for 8-12 hours, cool down and discharge the material. After post-processing, the reactive polymer flame retardant can be obtained.

[0019] As a further aspect of the present invention, in step S1, the reactive phosphorus-containing flame retardant is dimethyl phosphite or diethyl phosphite.

[0020] As a further aspect of the present invention, in step S2, the molar ratio of the connecting reagent and bibenzyloxydichlorosilane is 0.8-0.9:1.

[0021] As a further aspect of the present invention, in step S2, the acid-binding agent is triethylamine or pyridine.

[0022] As a further aspect of the present invention, the mass ratio of the aluminum silicate fiber to the reactive polymer flame retardant is 1:3-6.

[0023] In the above technical solution, a reactive phosphorus-containing flame retardant and glycidyl ether are first used as reactants. Under high temperature conditions, the pH in the reactive phosphorus-containing flame retardant structure and the epoxy group in the glycidyl ether structure undergo ring-opening to obtain a phosphorus-containing linking agent containing two equivalent hydroxyl substituents. Then, under the action of a fusible acid agent, the hydroxyl substituents in its structure can continuously replace the two equivalent silanine chloride groups in the bibenzyloxydichlorosilane structure to form a polymeric substance with a block alternating structure linked by silicon-oxygen bonds. In addition, by controlling the amount of reactants, the polymeric flame retardant can be made to exhibit silanine chloride end-capping to obtain a reactive polymeric flame retardant.

[0024] Finally, by utilizing the high reactivity of the terminal silane chloride groups of the reactive polymer flame retardant, the surface of the aluminosilicate fiber is modified to obtain aluminosilicate fiber with the surface coated with the polymer flame retardant, namely, aluminosilicate fiber modifying additive.

[0025] As a further embodiment of the present invention, the initiator is benzoyl peroxide or dicumyl peroxide; the antioxidant is at least one of antioxidant 1010, antioxidant 1076 or antioxidant 168; the inorganic filler is any one of talc, titanium dioxide, carbon black or fumed silica; and the lubricant is paraffin wax or polyethylene wax.

[0026] A fire-resistant cross-linked polyethylene for cable sheathing is produced using the above-mentioned manufacturing process.

[0027] (III) Beneficial Technical Effects

[0028] This invention modifies aluminosilicate fibers by modifying the surface of the fibers with a reactive polymeric flame retardant, thus creating an aluminosilicate fiber modifier. When mixed with high-density polyethylene (HDPE), the presence of the polymeric flame retardant creates a "transition" layer between the aluminosilicate fibers and the HDPE matrix, improving the interfacial bonding between them. Furthermore, during subsequent melt extrusion, the polymeric flame retardant molecular chains extend into various regions of the HDPE molecular chain network, forming a tightly connected, interlocking structure. This allows the aluminosilicate fibers to fully exert their reinforcing and modifying effects as inorganic fibers. In addition, the polymeric flame retardant itself contains a large amount of phosphorus and silicon flame-retardant elements. When the material burns, these elements rapidly form a dense carbon layer deposited with silicon oxides, preventing oxygen from entering and causing further combustion. They also prevent melt dripping. Combined with the effect of aluminosilicate fibers as an inorganic flame retardant, this effectively improves the flame-retardant performance of the material. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is an infrared analysis test image of a reactive polymeric flame retardant. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0032] Preparation Example 1

[0033] Preparation of aluminosilicate fiber modifying additives:

[0034] Add 3.5g of aluminosilicate fiber to a 1,4-dioxane solvent and sonicate at a frequency of 100kHz for 30 minutes. Then add 12g of reactive polymer flame retardant. After the addition is complete, stir evenly and purge with nitrogen for protection. Then gradually increase the temperature to 80℃ at a heating rate of 2℃ / min and keep it at that temperature for 8 hours. After that, remove the nitrogen and stop heating. Collect the material by centrifugation, and then wash and vacuum dry it to obtain the aluminosilicate fiber modified additive.

[0035] The specific preparation method of reactive polymeric flame retardants includes the following steps:

[0036] Step S1: Add 1.2g of dimethyl phosphite and 0.8g of glycidyl phosphate to toluene. After the addition is complete, start stirring and wait for a homogeneous reaction solution to form. Then, purge with nitrogen for protection, start heating, and maintain the temperature at 95℃. After stirring at this temperature for 8 hours, stop heating, cool down, discharge the material, collect the product, and obtain the ligation reagent.

[0037] Step S2: Mix 0.6g of the linking reagent, 1.2g of bis(benzyl)oxydichlorosilane and tetrahydrofuran, stir until a uniform mixture is formed, raise the temperature to 65°C, maintain this temperature for 4 hours, then add 0.1g of triethylamine to the mixture. After the addition is complete, continue to heat and stir for 9 hours, cool down and discharge the material. After post-processing, the reactive polymer flame retardant can be obtained.

[0038] Figure 1 This is an infrared analysis test image of a reactive polymeric flame retardant, where 3000 cm⁻¹ is the focal length. -1 ~3100cm -1 The absorption peak appearing at 2800 cm⁻¹ is the hydrocarbon absorption peak of the benzene ring skeleton. -1 ~3000cm -1 The absorption peak appearing at 1234 cm⁻¹ is a characteristic absorption peak of hydrocarbons in methyl and ethyl groups. -1 The absorption peak appearing at 1099 cm⁻¹ is a characteristic absorption peak of P=O. -1 The absorption peak appearing at this point is a characteristic absorption peak of Si-O.

[0039] Example 1

[0040] A fire-resistant cross-linked polyethylene insulation for cable sheathing is made from the following raw materials in parts by weight:

[0041]

[0042] The production process of the cross-linked polyethylene includes the following steps:

[0043] Step 1: Weigh all the ingredients according to the specified weight proportions and let them stand for later use;

[0044] The second step involves adding high-density polyethylene, nitrile rubber, and benzoyl peroxide into a torque rheometer, controlling the temperature at 180℃ and the rotation speed at 50 rpm, and then stopping the heating after 5 minutes of melt crosslinking polymerization, cooling down and discharging the material to form a polymer.

[0045] The third step involves adding the polymer material, compatibilizer, aluminum silicate fiber modifier, antioxidant 1010, talc, and paraffin wax into a mixer. After mechanically mixing at 100°C until homogeneous, the mixture is fed into an extruder. The temperatures of each zone are controlled sequentially as follows: 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, and 210±5°C. The screw speed is controlled at 100 r / min. After melt extrusion, cross-linked polyethylene can be obtained.

[0046] The compatibilizer is maleic anhydride-grafted polyethylene, with a maleic anhydride grafting rate of 0.8%; the preparation method of the aluminum silicate fiber modified additive is shown in Preparation Example 1, and the same applies to the following examples.

[0047] Example 2

[0048] A fire-resistant cross-linked polyethylene insulation for cable sheathing is made from the following raw materials in parts by weight:

[0049]

[0050] The production process of the cross-linked polyethylene includes the following steps:

[0051] Step 1: Weigh all the ingredients according to the specified weight proportions and let them stand for later use;

[0052] The second step involves adding high-density polyethylene, nitrile rubber, and benzoyl peroxide into a torque rheometer, controlling the temperature at 190℃ and the rotation speed at 60 rpm, and then melting and crosslinking polymerizing for 10 minutes. After this process, heating is stopped, the material is cooled and discharged to form a polymer.

[0053] The third step involves adding the polymer material, compatibilizer, aluminum silicate fiber modifier, antioxidant 1076, titanium dioxide, and polyethylene wax into a mixer. After mechanically mixing at 100°C until homogeneous, the mixture is fed into an extruder. The temperatures of each zone are controlled sequentially as follows: 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, and 210±5°C. The screw speed is controlled at 100 r / min. After melt extrusion, cross-linked polyethylene can be obtained.

[0054] Example 3

[0055] A fire-resistant cross-linked polyethylene insulation for cable sheathing is made from the following raw materials in parts by weight:

[0056]

[0057] The production process of the cross-linked polyethylene includes the following steps:

[0058] Step 1: Weigh all the ingredients according to the specified weight proportions and let them stand for later use;

[0059] The second step involves adding high-density polyethylene, nitrile rubber, and benzoyl peroxide into a torque rheometer, controlling the temperature at 190℃ and the rotation speed at 60 rpm, and then melting and crosslinking polymerizing for 10 minutes. After this process, heating is stopped, the material is cooled and discharged to form a polymer.

[0060] The third step involves adding the polymer material, compatibilizer, aluminum silicate fiber modifier, antioxidant 168, fumed silica, and polyethylene wax into a mixer. After mechanically mixing at 100°C until homogeneous, the mixture is fed into an extruder. The temperatures of each zone are controlled sequentially as follows: 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, and 210±5°C. The screw speed is controlled at 100 r / min. After melt extrusion, cross-linked polyethylene can be obtained.

[0061] Comparative Example 1

[0062] A fire-resistant cross-linked polyethylene insulation for cable sheathing is made from the following raw materials in parts by weight:

[0063]

[0064] The production process of the cross-linked polyethylene includes the following steps:

[0065] Step 1: Weigh all the ingredients according to the specified weight proportions and let them stand for later use;

[0066] The second step involves adding high-density polyethylene, nitrile rubber, and benzoyl peroxide into a torque rheometer, controlling the temperature at 190℃ and the rotation speed at 60 rpm, and then melting and crosslinking polymerizing for 10 minutes. After this process, heating is stopped, the material is cooled and discharged to form a polymer.

[0067] The third step involves adding the polymer material, compatibilizer, aluminum silicate fiber, antioxidant 1076, titanium dioxide, and polyethylene wax into a mixer. After mechanically mixing at 100°C until homogeneous, the mixture is fed into an extruder. The temperatures of each zone are controlled sequentially as follows: 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, and 210±5°C. The screw speed is controlled at 100 r / min. After melt extrusion, cross-linked polyethylene can be obtained.

[0068] Comparative Example 2

[0069] A fire-resistant cross-linked polyethylene insulation for cable sheathing is made from the following raw materials in parts by weight:

[0070]

[0071]

[0072] The production process of the cross-linked polyethylene includes the following steps:

[0073] Step 1: Weigh all the ingredients according to the specified weight proportions and let them stand for later use;

[0074] The second step involves adding high-density polyethylene, nitrile rubber, and benzoyl peroxide into a torque rheometer, controlling the temperature at 190℃ and the rotation speed at 60 rpm, and then melting and crosslinking polymerizing for 10 minutes. After this process, heating is stopped, the material is cooled and discharged to form a polymer.

[0075] The third step involves adding the polymer material, compatibilizer, reactive polymer flame retardant, antioxidant 1076, titanium dioxide, and polyethylene wax into a mixer. After mechanically mixing at 100°C until homogeneous, the mixture is fed into an extruder. The temperatures of each zone are controlled sequentially as follows: 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, and 210±5°C. The screw speed is controlled at 100 r / min. After melt extrusion, cross-linked polyethylene is obtained.

[0076] Test case

[0077] The cross-linked polyethylene samples used in the examples and comparative examples were injection molded to meet specifications, and various performance tests were conducted. The results are recorded in Table 1:

[0078] Table 1 - Test Results

[0079]

[0080]

[0081] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

[0082] Based on the preferred embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A production process for fire-resistant cross-linked polyethylene for cable sheathing, characterized in that, The cross-linked polyethylene is made from the following raw materials in parts by weight: 65-72 parts of high-density polyethylene; 5-15 parts compatibilizer; 3-5.5 parts of aluminum silicate fiber modifying additive; 5-10 parts of nitrile rubber; Initiator 0.1-0.2 parts; Antioxidant 0.5-1.5 parts; 5-9 parts of inorganic filler; 3-6 parts lubricant; The production process includes the following steps: Step 1: Weigh all the ingredients according to the specified weight proportions and let them stand for later use; The second step involves adding high-density polyethylene, nitrile rubber, and initiator into a torque rheometer, controlling the temperature at 180-190℃ and the rotation speed at 50-60 rpm, and then stopping the heating after 5-10 minutes of melt crosslinking polymerization, cooling down, and discharging the material to form a polymer. The third step involves adding the polymer material, compatibilizer, aluminum silicate fiber modifier, antioxidant, inorganic filler, and lubricant to a mixer. After mechanically mixing the mixture at 80-100℃, the mixture is fed into an extruder. The temperatures of each zone are controlled sequentially as follows: 190±5℃, 200±5℃, 210±5℃, 210±5℃, 220±5℃, and 210±5℃. The screw speed is controlled at 100-150 r / min. After melt extrusion, cross-linked polyethylene can be obtained. The specific preparation method of the aluminum silicate fiber modified additive is as follows: Aluminosilicate fibers are added to a 1,4-dioxane solvent and ultrasonically treated at an ultrasonic frequency of 80-100kHz for 20-40 minutes. Then, a reactive polymer flame retardant is added. After the addition is complete, the mixture is stirred evenly and protected with nitrogen gas. The temperature is then gradually increased to 70-80℃ at a heating rate of 2-3℃ / min and kept at this temperature for 6-9 hours. The nitrogen gas is then removed, heating is stopped, and the material is collected by centrifugation. After washing and vacuum drying, the aluminosilicate fiber modified additive can be obtained. The specific preparation method of the reactive polymeric flame retardant includes the following steps: Step S1: Add the reactive phosphorus-containing flame retardant and glycidol to toluene. After the addition is complete, start stirring and wait for a homogeneous reaction solution to form. Then, purge with nitrogen for protection, start heating, and maintain the temperature at 90-100℃. After stirring for 6-8 hours, stop heating, cool down and discharge the material, collect the product, and obtain the ligation reagent. Step S2: Mix the connecting reagent, bibenzyloxydichlorosilane and tetrahydrofuran, stir until uniform, raise the temperature to 60-65℃, maintain this temperature for 4-6 hours, then add the acid-binding agent to the mixture. After the addition is complete, continue to keep warm and stir for 8-12 hours, cool down and discharge the material. After post-processing, the reactive polymer flame retardant can be obtained.

2. The production process of fire-resistant cross-linked polyethylene for cable sheathing according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polyethylene or maleic anhydride-grafted polypropylene.

3. The production process of fire-resistant cross-linked polyethylene for cable sheathing according to claim 1, characterized in that, In step S1, the reactive phosphorus-containing flame retardant is dimethyl phosphite or diethyl phosphite.

4. The production process of fire-resistant cross-linked polyethylene for cable sheathing according to claim 1, characterized in that, In step S2, the molar ratio of the connecting reagent and bibenzoxydichlorosilane is 0.8-0.9:

1.

5. The production process of fire-resistant cross-linked polyethylene for cable sheathing according to claim 1, characterized in that, In step S2, the acid-binding agent is triethylamine or pyridine.

6. The production process of fire-resistant cross-linked polyethylene for cable sheathing according to claim 1, characterized in that, The mass ratio of the aluminum silicate fiber to the reactive polymer flame retardant is 1:3-6.

7. The production process of fire-resistant cross-linked polyethylene for cable sheathing according to claim 1, characterized in that, The initiator is benzoyl peroxide or dicumyl peroxide; the antioxidant is at least one of antioxidant 1010, antioxidant 1076 or antioxidant 168; the inorganic filler is any one of talc, titanium dioxide, carbon black or fumed silica; and the lubricant is paraffin wax or polyethylene wax.

8. A fire-resistant cross-linked polyethylene for cable sheathing, characterized in that, It is produced using the manufacturing process described in claim 1.

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