High temperature resistant flame-retardant polyolefin insulation material and preparation process thereof

Abstract

The application belongs to the technical field of materials, and particularly relates to a high-temperature-resistant flame-retardant polyolefin insulating material and a preparation process thereof. The polyolefin insulating material is prepared through pretreatment, mixing and extrusion granulation processes, and is prepared by taking high-density polyethylene as a base material and taking a flame-retardant crosslinking agent and the like as an additive. The flame-retardant crosslinking agent contains a large number of unsaturated alkenyl substituents in the structure, and can be crosslinked and polymerized with the polyethylene base material under the action of an initiator. First, after the base material molecular chain is crosslinked, the molecular chain density becomes large, and the chain movement of the molecular chain is more hindered under high-temperature conditions. Moreover, the flame-retardant crosslinking agent structure also contains a rigid benzene ring, which can improve the stability of the molecular chain under high-temperature conditions, thereby improving the high-temperature resistance of the material. Secondly, the flame-retardant crosslinking agent structure contains a large number of phosphate structures and nitrogen elements, which can quickly form an expanded carbon layer for protection when the material is on fire, thereby effectively enhancing the flame-retardant performance of the material.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a high-temperature resistant flame-retardant polyolefin insulating material and its preparation process. Background Technology

[0002] Polyolefin materials are widely used in the insulation and sheathing layers of wires and cables due to their excellent electrical insulation properties, chemical resistance, light weight, and good processability. Among them, polyethylene has superior rigidity and dielectric strength, making it one of the ideal matrix materials for preparing high-performance insulation materials.

[0003] However, with the increasing electrification of society and the increasingly stringent requirements for electrical safety, the insufficient dimensional stability and flame retardant properties of ordinary polyethylene materials under high-temperature environments have become increasingly prominent. Polyethylene is inherently flammable, and its limiting oxygen index is typically low. In the event of a fire, the material will burn rapidly, releasing large amounts of heat and smoke, posing a serious threat to personnel and property safety. Therefore, developing polyethylene insulation materials that combine high-temperature resistance and flame retardancy is of significant practical importance.

[0004] In existing technologies, one common method to improve the flame retardant properties of polyethylene materials is the addition of halogenated flame retardants. Although halogenated flame retardants have high flame retardant efficiency, they produce large amounts of toxic fumes and corrosive gases during combustion, seriously endangering the environment and personal safety, and their application is increasingly restricted. Therefore, developing halogen-free, low-smoke, and low-toxicity flame retardant systems has become a research hotspot in this field. Inorganic hydroxides (such as aluminum hydroxide and magnesium hydroxide) and phosphorus-nitrogen intumescent flame retardants are two main types of halogen-free flame retardants. However, inorganic hydroxides have low flame retardant efficiency and usually require high filler content to achieve the desired flame retardant effect, which severely deteriorates the mechanical properties and processing flowability of the material. Although intumescent flame retardants have higher efficiency, they have poor compatibility with polyolefin matrices and are prone to migration, affecting the long-term performance of the material and posing significant drawbacks in practical applications.

[0005] Based on this, the present invention provides a polyethylene insulation material with excellent high temperature resistance and flame retardant properties, solving the problems existing in the prior art. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a high-temperature resistant flame-retardant polyolefin insulation material and its preparation process.

[0007] In a first aspect, the present invention provides a high-temperature resistant, flame-retardant polyolefin insulating material, comprising, by weight parts, the following raw materials: High-density polyethylene: 86-98 parts; Linear low-density polyethylene: 25-36 parts; Flame-retardant crosslinking agent: 2-6.5 parts; Antioxidant: 0.3-0.5 parts; Lubricant: 1-2 parts; Initiator: 0.1-0.3 parts; Flame-retardant crosslinking agents are nitrogen-phosphorus synergistic flame retardants whose structures contain unsaturated alkenyl functional groups.

[0008] As a preferred embodiment of the present invention, the flame-retardant crosslinking agent is prepared by the following method: The diamine phosphorus-containing monomer, 1,4-dialdehyde-2,5-divinylbenzene, and N,N-dimethylformamide were added to the polymerization reactor. After the addition was complete, nitrogen gas was introduced as a protective gas, and stirring was started. After the mixture was homogeneous, the catalyst was added. After the addition was complete, the heating was started, and the temperature was raised to 60-80℃. The mixture was kept at this temperature and stirred for 18-24 hours. Heating was stopped, the solvent was evaporated, the product was collected, washed, and vacuum dried to obtain the flame-retardant crosslinking agent.

[0009] As a preferred embodiment of the present invention, the diamine phosphorus-containing monomer is prepared by the following method: Step 1: Add N-BOC-2-chloroethylamine and alkaline catalyst to N,N-dimethylformamide, stir and mix well, then add diethyl N,N-bis(2-hydroxyethyl)aminomethylenephosphonate. After the addition is complete, heat to 60-70℃, keep warm and stir for 4-8 hours, then evaporate the solvent, and purify the crude product by chromatographic column to obtain the precursor. Step 2: Add the precursor to dichloromethane, stir and mix well, place in an ice bath environment, slowly add the deprotection reagent dropwise, after the addition is complete, stir for 20-40 min, remove from the ice bath, continue stirring at room temperature for 0.5-1.5 h, evaporate the solvent, and wash and dry the crude product to obtain the diamine phosphorus-containing monomer.

[0010] As a preferred embodiment of the present invention, in step one, the molar ratio of N-BOC-2-chloroethylamine and N,N-bis(2-hydroxyethyl)aminomethylenephosphonic acid diethyl ester is 2:1.

[0011] As a preferred embodiment of the present invention, in step one, the alkaline catalyst is potassium carbonate or sodium carbonate.

[0012] As a preferred embodiment of the present invention, in step two, the deprotecting agent is trifluoroacetic acid.

[0013] As a preferred embodiment of the present invention, the molar ratio of the diamine phosphorus-containing monomer and 1,4-dialdehyde-2,5-divinylbenzene is 1:0.9-1.

[0014] As a preferred embodiment of the present invention, the catalyst is acetic acid.

[0015] It should be noted that in the above technical solution, a diamine phosphorus-containing monomer and 1,4-dialdehyde-2,5-divinylbenzene are used as reactants. Under the catalysis of acetic acid, the active amino substituents in the structures of the two can undergo a continuous Schiff base reaction with the aldehyde substituents, thereby producing a macromolecular nitrogen-phosphorus flame retardant with Schiff base as the linking bond and an alternating linkage structure, i.e., a flame-retardant crosslinking agent.

[0016] The diamine phosphorus-containing monomer is first prepared using N-BOC-2-chloroethylamine and diethyl N,N-bis(2-hydroxyethyl)aminomethylenephosphonate as raw materials. Under the catalysis of an alkaline catalyst, the halogen substituents and hydroxyl substituents in the structures of the two materials undergo a substitution reaction. By controlling the amount of the two materials, the active hydroxyl groups in the structure of diethyl N,N-bis(2-hydroxyethyl)aminomethylenephosphonate can be completely substituted to obtain the precursor. Then, the N-BOC is deprotected using a deprotecting agent to obtain a phosphonic acid derivative containing two equivalent active amino substituents, namely the diamine phosphorus-containing monomer.

[0017] As a preferred embodiment of the present invention, the antioxidant is at least one of hindered phenolic antioxidants; the lubricant is any one of stearic acid, zinc stearate, or calcium stearate; and the initiator is benzoyl peroxide or dicumyl peroxide.

[0018] A second aspect of the present invention provides a process for preparing a high-temperature resistant, flame-retardant polyolefin insulating material, comprising the following steps: Step 1: Add high-density polyethylene, linear low-density polyethylene, flame-retardant crosslinking agent and initiator to torque rheometer, raise the temperature to 160-180℃, keep it at the temperature for 10-20 minutes, then stop heating, cool down and discharge the material to form pretreated material; The second step involves adding the pretreated material, antioxidant, and lubricant to a mixer, mechanically stirring and mixing them evenly, and then transferring them to an extruder for melt extrusion granulation to obtain polyolefin insulation material.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The flame-retardant crosslinking agent prepared in this invention contains a large number of unsaturated alkenyl substituents, enabling it to crosslink and polymerize with a polyethylene substrate under the action of an initiator. Firstly, after crosslinking, the molecular chain density of the substrate increases, further hindering chain movement at high temperatures. Moreover, the flame-retardant crosslinking agent structure also contains rigid benzene rings, which enhance the stability of the molecular chains under high-temperature conditions, thereby improving the material's high-temperature resistance. Secondly, the flame-retardant crosslinking agent structure contains a large number of phosphate ester structures and nitrogen elements, which can rapidly form an expanded carbon layer for protection during combustion, effectively enhancing the material's flame-retardant properties. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is an infrared analysis diagram of a flame-retardant crosslinking agent. Detailed Implementation

[0022] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that the embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0023] Preparation Example Preparation of flame-retardant crosslinking agents: Step A: Add 0.5g of N-BOC-2-chloroethylamine and 0.2g of potassium carbonate to N,N-dimethylformamide, stir and mix well, then add 0.36g of N,N-bis(2-hydroxyethyl)aminomethylenephosphonic acid diethyl ester. After the addition is complete, heat to 65℃, keep warm and stir for 6h, then evaporate the solvent, and purify the crude product by chromatographic column to obtain the precursor; Step B: Add 0.4g of precursor to dichloromethane, stir and mix well, place in an ice bath environment, slowly add 1mL of trifluoroacetic acid, after the addition is complete, stir for 30min, remove from the ice bath, continue stirring at room temperature for 1h, evaporate the solvent, and wash and dry the crude product to obtain the diamine phosphorus-containing monomer. Step C: Add 0.4g of diamine phosphorus-containing monomer, 0.14g of 1,4-dialdehyde-2,5-divinylbenzene and N,N-dimethylformamide to the polymerization reactor. After the addition is complete, purge with nitrogen as a protective gas and start stirring. After the mixture is homogeneous, add 2mL of acetic acid. After the addition is complete, start heating and raise the temperature to 70℃. Continue stirring and maintaining the temperature for 24h. Stop heating, evaporate the solvent, collect the product, wash it, and vacuum dry it to obtain the flame-retardant crosslinking agent.

[0024] Figure 1 This is the infrared analysis test pattern of the flame-retardant crosslinking agent, where 3392 cm⁻¹... -1 and 3315cm -1 The characteristic absorption peak appearing at 1641 cm⁻¹ is the characteristic absorption peak of NH. -1 The characteristic absorption peak appearing at 1059 cm⁻¹ is the C=N characteristic absorption peak of Schiff bases. -1 The characteristic absorption peak appearing at this point is the CO characteristic absorption peak of the ether bond.

[0025] Example 1 This embodiment provides a high-temperature resistant, flame-retardant polyolefin insulation material, which, by weight, comprises the following raw materials: High-density polyethylene: 86 parts; Linear low-density polyethylene: 25 parts; Flame-retardant crosslinking agent: 2 parts; Antioxidant: 0.3 parts; Lubricant: 1 part; Initiator: 0.1 parts; The preparation method of polyolefin insulation material includes the following steps: Step 1: Add high-density polyethylene, linear low-density polyethylene, flame-retardant crosslinking agent and initiator to torque rheometer, raise the temperature to 160℃, keep it at the temperature for 20 minutes, then stop heating, cool down and discharge the material to form pretreated material; The second step involves adding the pretreated material, antioxidant, and lubricant to a mixer, mechanically stirring and mixing them evenly, and then transferring them to an extruder for melt extrusion granulation to obtain polyolefin insulation material.

[0026] The preparation method of the flame-retardant crosslinking agent is shown in the preparation example; antioxidant 1010 is selected as the antioxidant; zinc stearate is selected as the lubricant; benzoyl peroxide is selected as the initiator; the following are the same.

[0027] Example 2 This embodiment provides a high-temperature resistant, flame-retardant polyolefin insulation material, which, by weight, comprises the following raw materials: High-density polyethylene: 90 parts; Linear low-density polyethylene: 30 parts; Flame-retardant crosslinking agent: 5.5 parts; Antioxidant: 0.4 parts; Lubricant: 1.5 parts; Initiator: 0.2 parts; The preparation method of polyolefin insulation material includes the following steps: Step 1: Add high-density polyethylene, linear low-density polyethylene, flame-retardant crosslinking agent and initiator to torque rheometer, raise the temperature to 170℃, keep it at the temperature for 15 minutes, stop heating, cool down and discharge the material to form pretreated material; The second step involves adding the pretreated material, antioxidant, and lubricant to a mixer, mechanically stirring and mixing them evenly, and then transferring them to an extruder for melt extrusion granulation to obtain polyolefin insulation material.

[0028] Example 3 This embodiment provides a high-temperature resistant, flame-retardant polyolefin insulation material, which, by weight, comprises the following raw materials: High-density polyethylene: 98 parts; Linear low-density polyethylene: 36 parts; Flame-retardant crosslinking agent: 6.5 parts; Antioxidant: 0.5 parts; Lubricant: 2 parts; Initiator: 0.3 parts; The preparation method of polyolefin insulation material includes the following steps: Step 1: Add high-density polyethylene, linear low-density polyethylene, flame-retardant crosslinking agent and initiator to torque rheometer, raise the temperature to 180℃, keep it at the temperature for 10 minutes, stop heating, cool down and discharge the material to form pretreated material; The second step involves adding the pretreated material, antioxidant, and lubricant to a mixer, mechanically stirring and mixing them evenly, and then transferring them to an extruder for melt extrusion granulation to obtain polyolefin insulation material.

[0029] Comparative Example 1 The difference between this comparative example and Example 2 is that the flame-retardant crosslinking agent is replaced with 1,4-dialdehyde-2,5-divinylbenzene, otherwise they are the same.

[0030] Comparative Example 2 The difference between this comparative example and Example 2 is that the flame-retardant crosslinking agent and initiator are removed, while the rest are the same.

[0031] The polyolefin insulation materials provided in the above embodiments and comparative examples were subjected to performance tests, and the test methods are as follows: (1) The oxygen index was tested according to standard GB / T2406.2-2009; (2) Take the same mass of polyolefin insulation material samples, place them in an oven, control the heating rate to be 10℃ / min, and under nitrogen protection, raise the oven temperature from room temperature to 600℃. Record the temperature when the sample decomposes by 5% and record it as the initial decomposition temperature for high temperature resistance evaluation. The performance test data above are shown in Table 1.

[0032] Table 1 Performance Test Results Oxygen Index / % Initial decomposition temperature / °C Example 1 32.4 269 Example 2 32.8 271 Example 3 32.7 269 Comparative Example 1 18.9 262 Comparative Example 2 18.8 256 ; As can be seen from the above, the polyolefin insulation material prepared in the embodiments of the present invention has good flame retardant properties and high temperature resistance. After replacing the flame retardant crosslinking agent with 1,4-dialdehyde-2,5-divinylbenzene, although it can still play a certain crosslinking role, it does not contain nitrogen and phosphorus flame retardant elements, and the degree of crosslinking is low, which leads to a reduction in the flame retardant properties and high temperature resistance of the material to varying degrees.

[0033] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also 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 for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A high-temperature resistant, flame-retardant polyolefin insulating material, characterized in that, Measured by weight, it includes the following raw materials: High-density polyethylene: 86-98 parts; Linear low-density polyethylene: 25-36 parts; Flame-retardant crosslinking agent: 2-6.5 parts; Antioxidant: 0.3-0.5 parts; Lubricant: 1-2 parts; Initiator: 0.1-0.3 parts; The flame-retardant crosslinking agent is a nitrogen-phosphorus synergistic flame retardant containing unsaturated alkenyl functional groups in its structure.

2. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 1, characterized in that, The flame-retardant crosslinking agent is prepared using the following method: The diamine phosphorus-containing monomer, 1,4-dialdehyde-2,5-divinylbenzene, and N,N-dimethylformamide were added to the polymerization reactor. After the addition was complete, nitrogen gas was introduced as a protective gas, and stirring was started. After the mixture was homogeneous, the catalyst was added. After the addition was complete, the heating was started, and the temperature was raised to 60-80℃. The mixture was kept at this temperature and stirred for 18-24 hours. Heating was stopped, the solvent was evaporated, the product was collected, washed, and vacuum dried to obtain the flame-retardant crosslinking agent.

3. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 2, characterized in that, The diamine phosphorus-containing monomer is prepared by the following method: Step 1: Add N-BOC-2-chloroethylamine and alkaline catalyst to N,N-dimethylformamide, stir and mix well, then add diethyl N,N-bis(2-hydroxyethyl)aminomethylenephosphonate. After the addition is complete, heat to 60-70℃, keep warm and stir for 4-8 hours, then evaporate the solvent, and purify the crude product by chromatographic column to obtain the precursor. Step 2: Add the precursor to dichloromethane, stir and mix well, place in an ice bath environment, slowly add the deprotection reagent dropwise, after the addition is complete, stir for 20-40 min, remove from the ice bath, continue stirring at room temperature for 0.5-1.5 h, evaporate the solvent, and wash and dry the crude product to obtain the diamine phosphorus-containing monomer.

4. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 3, characterized in that, In step one, the molar ratio of N-BOC-2-chloroethylamine and N,N-bis(2-hydroxyethyl)aminomethylenephosphonate diethyl ester is 2:

1.

5. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 3, characterized in that, In step one, the alkaline catalyst is potassium carbonate or sodium carbonate.

6. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 3, characterized in that, In step two, the deprotection agent is trifluoroacetic acid.

7. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 2, characterized in that, The molar ratio of the diamine phosphorus-containing monomer and 1,4-dialdehyde-2,5-divinylbenzene is 1:0.9-1.

8. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 2, characterized in that, The catalyst is acetic acid.

9. The high-temperature resistant flame-retardant polyolefin insulation material according to claim 1, characterized in that, The antioxidant is at least one of hindered phenolic antioxidants; the lubricant is any one of stearic acid, zinc stearate, or calcium stearate; and the initiator is benzoyl peroxide or dicumyl peroxide.

10. A preparation process for the high-temperature resistant flame-retardant polyolefin insulation material as described in claim 1, characterized in that, Includes the following steps: Step 1: Add high-density polyethylene, linear low-density polyethylene, flame-retardant crosslinking agent and initiator to torque rheometer, raise the temperature to 160-180℃, keep it at the temperature for 10-20 minutes, then stop heating, cool down and discharge the material to form pretreated material; The second step involves adding the pretreated material, antioxidant, and lubricant to a mixer, mechanically stirring and mixing them evenly, and then transferring them to an extruder for melt extrusion granulation to obtain polyolefin insulation material.

Images