Insulating fire-resistant crosslinked polyethylene for cable sheath and production process of insulating fire-resistant crosslinked polyethylene

Abstract

The invention relates to the technical field of materials, and discloses insulating fire-resistant crosslinked polyethylene for a cable sheath and a production process thereof.The crosslinked polyethylene is prepared by taking high-density polyethylene as a main raw material and taking a compatilizer, an aluminum silicate fiber modified additive and a nitrile rubber lamp as auxiliary materials through melt cross-linking polymerization and then blending extrusion. Wherein the aluminum silicate fiber modified additive is aluminum silicate fiber of which the surface is modified by a reaction type high-molecular flame retardant, and the existence of the high-molecular flame retardant is equivalent to that a transition layer is generated between the aluminum silicate fiber and a high-density polyethylene matrix, so that the interface bonding property between the aluminum silicate fiber and the high-density polyethylene is improved; and the macromolecular flame retardant contains a large amount of phosphorus and silicon flame-retardant elements, so that the flame-retardant and fire-resistant properties of the crosslinked polyethylene can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to an insulating fire-resistant cross-linked polyethylene for cable sheath and a production process thereof. Background Art

[0002] Cables are a vital component in power and communication systems, and cable sheaths are responsible for protecting the internal structure of cables, enhancing the mechanical strength and corrosion resistance of cables. At present, cables are generally composed of conductors, insulation layers, isolation layers and outer sheaths. The insulation layer is generally formed by coating the outside of the conductor with minerals such as mica. The existence of this insulation layer can give the cable a good explosion-proof effect. The isolation layer is generally made of metal aluminum. The outer sheath is generally made of polymer materials such as polyethylene as cable sheath materials. However, in some special industries, such as the petrochemical industry, cables need to withstand long-term erosion by corrosive media such as petroleum and chemicals, which requires cable sheath materials to have better corrosion resistance. However, the oil resistance and corrosion resistance of polyethylene sheath materials are generally not able to meet the demand, and it is difficult to ensure the safe and reliable operation of cables in harsh environments. Compared with conventional polyethylene, cross-linked polyethylene has better heat resistance, mechanical strength and chemical resistance, and also has good insulation performance, so it can meet the needs of harsher use environments.

[0003] In addition, 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 has relatively excellent comprehensive performance, it is a flammable material and is very easy to burn. It will also be accompanied by molten dripping, causing the fire to spread, so there is a large safety hazard. At this stage, the flame retardant and fire retardant properties of cross-linked polyethylene are generally improved by adding flame retardants, such as inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide, and organic phosphorus flame retardants such as DOPO, etc. However, inorganic flame retardants are relatively ineffective and require a large amount of addition to have a certain effect, which will have an impact on the mechanical properties of polymer materials. Although organic phosphorus flame retardants such as DOPO have good flame retardant modification effects, they are easy to volatilize and migrate, and it is difficult to ensure the long-term flame retardant effect of the material. Based on this, the present invention provides an insulating fire-resistant cross-linked polyethylene with excellent flame retardant and fire retardant properties, which can be directly used to make cable sheaths. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides an insulating fire-resistant cross-linked polyethylene for cable sheath and a production process thereof.

[0006] (II) Technical solution

[0007] A production process of fire-resistant cross-linked polyethylene for cable sheath insulation, wherein the cross-linked polyethylene is made of the following raw materials in parts by weight:

[0008]

[0009] The production process comprises the following steps:

[0010] The first step is to weigh each raw material according to the weight and set it aside for later use;

[0011] Step 2: Add high-density polyethylene, nitrile rubber and initiator into the torque rheometer, control the temperature to 180-190°C, the speed to 50-60rpm, melt cross-linking polymerization for 5-10 minutes, stop heating, cool down and discharge to form a polymer material;

[0012] The third step is to add polymer material, compatibilizer, aluminum silicate fiber modification additive, antioxidant, inorganic filler and lubricant into the mixer, stir and mix them evenly at 80-100°C, then feed them into the extruder, control the temperature of each zone to 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, 210±5°C, and the screw speed to 100-150r / min, and obtain cross-linked polyethylene through melt extrusion.

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

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

[0015] Aluminum silicate fiber is added to 1,4-dioxane solvent, and ultrasonically treated at an ultrasonic frequency of 80-100kHz for 20-40 minutes, and then a reactive polymer flame retardant is added. After the addition is completed, the mixture is stirred evenly, and nitrogen is introduced for protection. Then, the temperature is gradually increased to 70-80°C at a heating rate of 2-3°C / min. After heat preservation for 6-9 hours, the nitrogen is removed, the heating is stopped, the material is collected by centrifugation, and then washed and vacuum dried to obtain the aluminum silicate fiber modified additive.

[0016] As a further embodiment of the present invention, the specific preparation method of the reactive polymer flame retardant comprises the following steps:

[0017] Step S1: adding a reactive phosphorus-containing flame retardant and glycidol to toluene, stirring after the addition is completed, and until a uniform reaction liquid is formed, nitrogen protection is introduced, heating is started, and the temperature is maintained at 90-100° C. After stirring for 6-8 hours, heating is stopped, the temperature is lowered, the material is discharged, and the product is collected to obtain a connecting reagent;

[0018] Step S2, mixing the linking reagent, dichlorodibenzylsilane and tetrahydrofuran, stirring until uniformly mixed, raising the temperature to 60-65°C, maintaining the temperature for 4-6 hours, then adding the acid binding agent to the mixed solution, and after the addition, continuing to keep the temperature and stir for 8-12 hours, cooling and discharging, and after post-treatment, the reactive polymer flame retardant can be obtained.

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

[0020] As a further embodiment of the present invention, in step S2, the molar ratio of the linking reagent to dichlorodibenzylsilane is 0.8-0.9:1.

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

[0022] As a further solution 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 scheme, a reactive phosphorus-containing flame retardant and glycidol are first used as reactants. Under high temperature conditions, the PH in the structure of the reactive phosphorus-containing flame retardant and the epoxy group in the glycidol structure are ring-opened to obtain a phosphorus-containing linking reagent containing two equivalents of hydroxyl substituents in the structure. Then, under the action of an acidifying agent, the hydroxyl substituents in the structure can be continuously substituted with two equivalents of silicon-chloride groups in the structure of dichlorodibenzylsilane to form a polymer substance connected by silicon-oxygen bonds and having a block alternating structure. In addition, by controlling the amount of the reactants, the polymer flame retardant can be made to exhibit silicon-chloride end-capping to obtain a reactive polymer flame retardant.

[0024] Finally, the aluminum silicate fiber is surface-modified by utilizing the high reactivity of the silicon-chlorine group at the end of the reactive polymer flame retardant to obtain the aluminum silicate fiber with the surface coated with the polymer flame retardant, namely, the aluminum silicate fiber modification additive.

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

[0026] The invention discloses an insulating fire-resistant cross-linked polyethylene for cable sheath, which is produced by adopting the production process.

[0027] (III) Beneficial technical effects

[0028] The present invention prepares aluminum silicate fiber modified additive by modifying the surface of aluminum silicate fiber with reactive polymer flame retardant, and mixes it with high-density polyethylene. The presence of polymer flame retardant is equivalent to producing a "transition" layer between aluminum silicate fiber and high-density polyethylene matrix, which is beneficial to improving the interface bonding between aluminum silicate fiber and high-density polyethylene, and in the subsequent melt extrusion process, the polymer flame retardant molecular chain will extend to each area of ​​the high-density polyethylene molecular chain network, forming a tightly connected snap-on structure with each other, so that aluminum silicate fiber can give full play to its enhanced modification effect as inorganic fiber. In addition, the polymer flame retardant itself contains a large amount of phosphorus and silicon flame retardant elements in its structure. When the material burns, these flame retardant elements quickly form a dense carbon layer with silicon oxide deposited thereon, preventing oxygen from entering the interior to cause continued combustion, and also preventing the melting drop phenomenon, and cooperating with the effect of aluminum silicate fiber as an inorganic flame retardant, effectively improving the flame retardant effect of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0030] Figure 1 This is the infrared analysis test diagram of reactive polymer flame retardant. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. Preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0032] Preparation Example 1

[0033] Preparation of aluminum silicate fiber modified additives:

[0034] 3.5 g of aluminum silicate fiber is added to 1,4-dioxane solvent, and ultrasonically treated at an ultrasonic frequency of 100 kHz for 30 minutes. Then, 12 g of reactive polymer flame retardant is added. After the addition is completed, the mixture is stirred evenly, and nitrogen is introduced for protection. Then, the temperature is gradually increased to 80°C at a heating rate of 2°C / min. After heat preservation for 8 hours, the nitrogen is removed, the heating is stopped, the material is collected by centrifugation, and then washed and vacuum dried to obtain the aluminum silicate fiber modified additive.

[0035] The specific preparation method of the reactive polymer flame retardant comprises the following steps:

[0036] Step S1: 1.2 g of dimethyl phosphite and 0.8 g of glycidol were added to toluene. After the addition was completed, stirring was started. When a uniform reaction liquid was formed, nitrogen was introduced for protection. Heating was started and the temperature was maintained at 95° C. After stirring for 8 h, heating was stopped, the temperature was lowered, the product was collected, and a connecting reagent was obtained.

[0037] Step S2, 0.6g of the linking reagent, 1.2g of dichlorobenzylsilane and tetrahydrofuran are mixed, stirred until uniformly mixed, the temperature is raised to 65°C, maintained at this temperature for 4h, and then 0.1g of triethylamine is added to the mixed solution. After the addition is completed, the mixture is kept warm and stirred for 9h, the temperature is lowered and the material is discharged. After post-treatment, a reactive polymer flame retardant can be obtained.

[0038] Figure 1 This is the infrared analysis test chart of reactive polymer flame retardant, where 3000cm -1 ~3100cm -1 The absorption peak at 2800 cm is the carbon-hydrogen absorption peak of the benzene ring skeleton. -1 ~3000cm -1 The absorption peak at 1234 cm is the characteristic absorption peak of carbon and hydrogen in methyl and ethyl. -1 The absorption peak at 1099cm is the characteristic absorption peak of P=O. -1 The absorption peak that appears at is the Si-O characteristic absorption peak.

[0039] Example 1

[0040] An insulating fire-resistant cross-linked polyethylene for cable sheath, made from the following raw materials in parts by weight:

[0041]

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

[0043] The first step is to weigh each raw material according to the weight and set it aside for later use;

[0044] Step 2: Add high-density polyethylene, nitrile rubber and benzoyl peroxide into the torque rheometer, control the temperature to 180°C, the speed to 50 rpm, melt cross-linking polymerization for 5 minutes, stop heating, cool down and discharge to form a polymer material;

[0045] The third step is to add polymer material, compatibilizer, aluminum silicate fiber modification additive, antioxidant 1010, talcum powder and paraffin into the mixer, stir and mix them evenly at 100°C, then feed them into the extruder, control the temperature of each zone to 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, 210±5°C, and the screw speed to 100r / min, and obtain cross-linked polyethylene after melt extrusion.

[0046] The compatibilizer is maleic anhydride grafted polyethylene, and the grafting rate of maleic anhydride is 0.8%. The preparation method of the aluminum silicate fiber modified additive is shown in Preparation Example 1, and the same is true for the following.

[0047] Example 2

[0048] An insulating fire-resistant cross-linked polyethylene for cable sheath, made from the following raw materials in parts by weight:

[0049]

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

[0051] The first step is to weigh each raw material according to the weight and set it aside for later use;

[0052] Step 2: Add high-density polyethylene, nitrile rubber and benzoyl peroxide into the torque rheometer, control the temperature to 190°C, the speed to 60rpm, melt cross-linking polymerization for 10 minutes, stop heating, cool down and discharge to form a polymer material;

[0053] The third step is to add polymer material, compatibilizer, aluminum silicate fiber modification additive, antioxidant 1076, titanium dioxide and polyethylene wax into the mixer, stir mechanically at 100°C to mix evenly, feed into the extruder, control the temperature of each zone to 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, 210±5°C, and the screw speed to 100r / min, and obtain cross-linked polyethylene through melt extrusion.

[0054] Example 3

[0055] An insulating fire-resistant cross-linked polyethylene for cable sheath, made from the following raw materials in parts by weight:

[0056]

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

[0058] The first step is to weigh each raw material according to the weight and set it aside for later use;

[0059] Step 2: Add high-density polyethylene, nitrile rubber and benzoyl peroxide into the torque rheometer, control the temperature to 190°C, the speed to 60rpm, melt cross-linking polymerization for 10 minutes, stop heating, cool down and discharge to form a polymer material;

[0060] The third step is to add polymer material, compatibilizer, aluminum silicate fiber modification additive, antioxidant 168, fumed silica and polyethylene wax into a mixer, stir mechanically at 100°C to mix evenly, feed into an extruder, control the temperature of each zone to 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, 210±5°C, and the screw speed to 100r / min, and obtain cross-linked polyethylene through melt extrusion.

[0061] Comparative Example 1

[0062] An insulating fire-resistant cross-linked polyethylene for cable sheath, made from the following raw materials in parts by weight:

[0063]

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

[0065] The first step is to weigh each raw material according to the weight and set it aside for later use;

[0066] Step 2: Add high-density polyethylene, nitrile rubber and benzoyl peroxide into the torque rheometer, control the temperature to 190°C, the speed to 60rpm, melt cross-linking polymerization for 10 minutes, stop heating, cool down and discharge to form a polymer material;

[0067] The third step is to add polymer material, compatibilizer, aluminum silicate fiber, antioxidant 1076, titanium dioxide and polyethylene wax into the mixer, stir mechanically at 100°C to mix evenly, feed into the extruder, control the temperature of each zone to 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, 210±5°C, and the screw speed to 100r / min, and obtain cross-linked polyethylene through melt extrusion.

[0068] Comparative Example 2

[0069] An insulating fire-resistant cross-linked polyethylene for cable sheath, made from the following raw materials in parts by weight:

[0070]

[0071]

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

[0073] The first step is to weigh each raw material according to the weight and set it aside for later use;

[0074] Step 2: Add high-density polyethylene, nitrile rubber and benzoyl peroxide into the torque rheometer, control the temperature to 190°C, the speed to 60rpm, melt cross-linking polymerization for 10 minutes, stop heating, cool down and discharge to form a polymer material;

[0075] The third step is to add polymer material, compatibilizer, reactive polymer flame retardant, antioxidant 1076, titanium dioxide and polyethylene wax into the mixer, stir mechanically at 100°C to mix evenly, feed into the extruder, control the temperature of each zone to 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, 210±5°C, and the screw speed to 100r / min, and obtain cross-linked polyethylene through melt extrusion.

[0076] Test Case

[0077] The cross-linked polyethylene in the examples and comparative examples was injection molded into test samples that met the specifications, and various performance tests were performed. The results are recorded in Table 1:

[0078] Table 1 - Test results

[0079]

[0080]

[0081] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

[0082] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A production process of fire-resistant cross-linked polyethylene for cable sheath insulation, characterized in that: The cross-linked polyethylene is made of the following raw materials in parts by weight: The production process comprises the following steps: The first step is to weigh each raw material according to the weight and set it aside for later use; Step 2: Add high-density polyethylene, nitrile rubber and initiator into the torque rheometer, control the temperature to 180-190°C, the speed to 50-60rpm, melt cross-linking polymerization for 5-10 minutes, stop heating, cool down and discharge to form a polymer material; The third step is to add polymer material, compatibilizer, aluminum silicate fiber modification additive, antioxidant, inorganic filler and lubricant into the mixer, stir and mix them evenly at 80-100°C, then feed them into the extruder, control the temperature of each zone to 190±5°C, 200±5°C, 210±5°C, 210±5°C, 220±5°C, 210±5°C, and the screw speed to 100-150r / min, and obtain cross-linked polyethylene through melt extrusion.

2. The production process of fire-resistant cross-linked polyethylene for cable sheath 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 sheath according to claim 1, characterized in that: The specific preparation method of the aluminum silicate fiber modified additive is as follows: Aluminum silicate fiber is added to 1,4-dioxane solvent, and ultrasonically treated at an ultrasonic frequency of 80-100kHz for 20-40 minutes, and then a reactive polymer flame retardant is added. After the addition is completed, the mixture is stirred evenly, and nitrogen is introduced for protection. Then, the temperature is gradually increased to 70-80°C at a heating rate of 2-3°C / min. After heat preservation for 6-9 hours, the nitrogen is removed, the heating is stopped, the material is collected by centrifugation, and then washed and vacuum dried to obtain the aluminum silicate fiber modified additive.

4. The production process of fire-resistant cross-linked polyethylene for cable sheath according to claim 3, characterized in that: The specific preparation method of the reactive polymer flame retardant comprises the following steps: Step S1: adding a reactive phosphorus-containing flame retardant and glycidol to toluene, stirring after the addition is completed, and until a uniform reaction liquid is formed, nitrogen protection is introduced, heating is started, and the temperature is maintained at 90-100° C. After stirring for 6-8 hours, heating is stopped, the temperature is lowered, the material is discharged, and the product is collected to obtain a connecting reagent; Step S2, mixing the linking reagent, dichlorodibenzylsilane and tetrahydrofuran, stirring until uniformly mixed, raising the temperature to 60-65°C, maintaining the temperature for 4-6 hours, then adding the acid binding agent to the mixed solution, and after the addition, continuing to keep the temperature and stir for 8-12 hours, cooling and discharging, and after post-treatment, the reactive polymer flame retardant can be obtained.

5. The production process of fire-resistant cross-linked polyethylene for cable sheath according to claim 4, characterized in that: In step S1, the reactive phosphorus-containing flame retardant is dimethyl phosphite or diethyl phosphite.

6. The production process of fire-resistant cross-linked polyethylene for cable sheath according to claim 4, characterized in that: In step S2, the molar ratio of the linking reagent to dichlorodibenzylsilane is 0.8-0.9:

1.

7. The production process of fire-resistant cross-linked polyethylene for cable sheath according to claim 4, characterized in that: In step S2, the acid binding agent is triethylamine or pyridine.

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

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

10. A fire-resistant cross-linked polyethylene for cable sheath insulation, characterized in that: The method is prepared by the production process as claimed in claim 1.

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