Insulating composite material for electric wires and method for producing the same

Abstract

This invention relates to the field of insulating composite materials technology, and discloses an insulating composite material for wires and its preparation method. The insulating composite material contains additives such as insulating modified filler and flame-retardant filler, and is prepared by melting. The insulating modified filler has a rigid structure, which can improve the intrinsic strength and thermodynamic stability of the matrix, suppress polarization relaxation and charge injection under an electric field, and improve the breakdown field strength. At the same time, boehmite is uniformly dispersed in the matrix, which plays a role in optimizing the electric field distribution and constructing a microscopic barrier. The flame-retardant filler contains nitrogen and phosphorus elements. When combustion occurs, the flame-retardant filler is heated to produce phosphoric acid, forming a molten carbon layer, and nitrogen gas is generated at the same time. Under the impetus of a large amount of gas inside, the molten carbon layer expands rapidly to form a dense and solid expanded carbon layer, which plays a role in heat insulation and oxygen isolation, and prevents further combustion.

Description

Technical Field

[0001] This invention relates to the field of insulating composite materials technology, specifically to an insulating composite material for electrical wires and its preparation method. Background Technology

[0002] Polypropylene, as a general-purpose plastic with excellent comprehensive properties, has become an important base material choice for wire and cable insulation layers due to its good processing fluidity, low density, and cost advantages. In flexible electric heating appliances such as electric blankets and electric heating pads, polypropylene serves as the heating wire that comes into direct or indirect contact with the human body. Therefore, the reliability and flame-retardant safety of its insulation layer are decisive factors concerning the safety of life and property.

[0003] However, polypropylene's insulation properties are insufficient under high-voltage direct current (HVDC) electric fields. Under long-term HVDC stress, space charge easily accumulates inside polypropylene. These retained charges severely distort the electric field distribution within the material, causing local electric field strengths to far exceed the design average. This distortion not only accelerates the aging of the insulation material but also induces the phenomenon of "electrical trees," which originates from microscopic defects or impurities. Once initiated, electrical trees grow irreversibly within the insulation in the form of branched channels, ultimately leading to premature breakdown of the insulation layer and posing a direct threat to the safety and lifespan of the entire power transmission system.

[0004] Meanwhile, polypropylene is inherently a flammable material. In scenarios such as dense cable laying or enclosed spaces, if it overheats due to a fault or encounters an external fire source, the material is prone to combustion, accompanied by molten droplets, which may cause the fire to spread, making it difficult to meet increasingly stringent electrical safety and fire prevention standards. Therefore, it is necessary to simultaneously perform targeted insulation and flame-retardant modifications on it.

[0005] The invention patent with application number CN202510365215.1 discloses a method for preparing polypropylene cable insulation resin and the polypropylene cable insulation resin, which solves the problems of poor toughness, poor electrical insulation performance and low melt strength of existing polypropylene. However, it fails to modify the flame retardant properties of polypropylene materials. Based on this, the present invention provides an insulating composite material that has both excellent insulation and flame retardant properties. Summary of the Invention

[0006] The purpose of this invention is to provide an insulating composite material for electrical wires and a method for preparing the same.

[0007] The objective of this invention can be achieved through the following technical solutions: An insulating composite material for electrical wires comprises the following raw materials in parts by weight: 50-80 parts polypropylene, 10-20 parts compatibilizer, 1-3 parts antioxidant, 2-5 parts insulating modified filler, 5-9 parts flame retardant filler.

[0008] Furthermore, the compatibilizer is maleic anhydride-grafted polypropylene; the antioxidant is antioxidant 1010 or antioxidant 1076.

[0009] Furthermore, the preparation method of the insulating modified filler includes the following steps: A1. Take 1.2-1.9g of boehmite and add it to 100ml of deionized water. After ultrasonic dispersion, a boehmite dispersion is obtained. Take 0.2-0.3g of diacid linker and 0.01-0.02g of acidic catalyst and add them to the boehmite dispersion. Stir and heat to 70-80℃, keep warm and stir for 10-12h. After the reaction is completed, filter, wash and dry to obtain modified boehmite. A2. Take 1.1-1.5g of modified boehmite and add it to 100ml of N,N-dimethylformamide. Disperse it evenly by ultrasonication to obtain a modified boehmite dispersion. Take 1.36-1.89g of 2,3,6,7-tetraaminoanthracene-9,10-dione and add it to the modified boehmite dispersion. Heat to 80-90℃ and stir for 1-2h. Then add 1.7-2.1g of 4,4'-tetraphenylsilanedicarboxylic acid and continue stirring at this temperature for 8-12h. Then heat to 120-140℃ and stir for 5-10h. After the reaction is completed, filter, wash and dry to obtain the insulating modified filler.

[0010] Furthermore, in A1, the acidic catalyst is p-toluenesulfonic acid or aminosulfonic acid.

[0011] Furthermore, in A1, the diacid linker is succinic acid or glutaric acid.

[0012] Further, in A2, the mass ratio of the 4,4'-tetraphenylsilanedicarboxylic acid and the 2,3,6,7-tetraaminoanthracene-9,10-dione is 1:0.8-0.9.

[0013] The above technical solution involves esterifying the hydroxyl groups of boehmite with the carboxyl groups of a diacid binder to graft carboxyl groups onto the surface of boehmite, thereby obtaining modified boehmite. Then, 4,4'-tetraphenylsilanedicarboxylic acid and 2,3,6,7-tetraaminoanthracene-9,10-dione are polymerized on the surface of the modified boehmite to end it with amino groups. The insulating modified filler is then attached to the polypropylene molecular chain via a binder.

[0014] Furthermore, the preparation method of the flame-retardant filler includes the following steps: B1. Take 1.7-2.6g of 5,5-dimethyl-1,3-di(epoxyethylenemethyl)imidazolidine-2,4-dione and add it to 50ml of dimethyl sulfoxide. After stirring evenly, add 0.76-1.9g of pyridine-2,4-diol and 0.1-0.2g of accelerator. Heat to 130-140℃ and stir continuously for 6-10h. After the reaction is completed, remove the solvent, wash and dry to obtain the nitrogen-containing polymer. B2. Take 4.2-11.2g of nitrogen-containing polymer and add it to 50ml of N,N-dimethylformamide. Stir until completely dissolved, then add 0.3-0.8g of 3-hydroxyphenylphosphonopropionic acid and 0.2-0.4g of p-toluenesulfonic acid. Heat to 60-70℃ and stir at this temperature for 8-12h. After the reaction is complete, remove the solvent, wash and dry to obtain the flame-retardant filler.

[0015] Furthermore, in B1, the accelerator is triphenylphosphine.

[0016] Further, in B1, the mass ratio of 5,5-dimethyl-1,3-di(epoxyethylenemethyl)imidazolidine-2,4-dione to pyridine-2,4-diol is 1:0.45-0.73.

[0017] Through the above technical solution, the epoxy of 5,5-dimethyl-1,3-di(epoxyethylenemethyl)imidazolidine-2,4-dione and pyridine-2,4-diol are polymerized, and each epoxy retains a hydroxyl group, which reacts with the carboxyl group of 3-hydroxyphenylphosphonopropionic acid to obtain a flame-retardant filler.

[0018] A method for preparing an insulating composite material for electrical wires includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, insulating modified filler, and flame retardant filler to a mixer and stir evenly at a speed of 400-600 r / min to obtain a premix. Step 2: Add the premixed material to a mixer and mix at a speed of 40-60 r / min for 15-20 min. Then feed it into a twin-screw extruder at a speed of 40-80 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

[0019] The beneficial effects of this invention are: (1) The insulating composite material prepared by the present invention uses polypropylene as the base material and includes insulating modified filler and flame retardant filler. It is prepared by melting and has excellent insulation and flame retardancy.

[0020] (2) Among them, the insulating modified filler is prepared by polymerization of 4,4'-tetraphenylsilanedicarboxylic acid and 2,3,6,7-tetraaminoanthracene-9,10-dione on the surface of modified boehmite. The insulating modified filler is introduced into the polypropylene molecular chain by a crosslinking agent. The insulating modified filler has a rigid structure, which can improve the intrinsic strength and thermodynamic stability of the matrix. This reinforcement can effectively "lock" the molecular chain and significantly inhibit its polarization relaxation and charge injection under the electric field, thereby improving the intrinsic breakdown field strength of the matrix. At the same time, boehmite is an insulating nanoparticle that is uniformly dispersed in the polypropylene matrix, playing the role of optimizing the electric field distribution and constructing a micro barrier.

[0021] (3) The flame retardant filler contains nitrogen and phosphorus elements. When combustion occurs, the flame retardant filler is heated to produce phosphoric acid, which transforms the originally flammable polypropylene molecular chain into carbon-rich, non-volatile carbon residue, forming a molten carbon layer. This provides the material basis for the subsequent formation of an expanded carbon layer. At the same time, nitrogen gas is generated when heated. Under the impetus of a large amount of gas inside, the molten carbon layer expands rapidly to form a dense and solid expanded carbon layer, which plays the role of heat insulation and oxygen isolation, preventing further combustion.

[0022] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] An insulating composite material for electrical wires comprises the following raw materials in parts by weight: 50 parts polypropylene, 10 parts compatibilizer, 1 part antioxidant, 2 parts insulating modified filler, 5 parts flame retardant filler; The preparation method of the insulating composite material includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, insulating modified filler, and flame retardant filler to a mixer and stir evenly at a speed of 400 r / min to obtain a premix. Step 2: Add the premixed material to the internal mixer and mix at a speed of 40 r / min for 15 min. Then feed it into the twin-screw extruder at a speed of 40 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

[0026] The preparation method of the insulating modified filler includes the following steps: A1. Take 1.2g of boehmite and add it to 100ml of deionized water. After ultrasonic dispersion, a boehmite dispersion is obtained. Take 0.2g of succinic acid and 0.01g of p-toluenesulfonic acid and add them to the boehmite dispersion. Stir and heat to 70℃, keep warm and stir for 12h. After the reaction is completed, filter, wash and dry to obtain modified boehmite. A2. Take 1.3g of modified boehmite and add it to 100ml of N,N-dimethylformamide. Disperse it evenly by ultrasonication to obtain a modified boehmite dispersion. Take 1.4g of 2,3,6,7-tetraaminoanthracene-9,10-dione and add it to the modified boehmite dispersion. Heat to 90℃ and stir for 1h. Then add 1.7g of 4,4'-tetraphenylsilanedicarboxylic acid and continue stirring at this temperature for 8h. Then heat to 130℃ and stir for 7h. After the reaction is completed, filter, wash and dry to obtain the insulating modified filler.

[0027] Among them, the CAS number of 2,3,6,7-tetraaminoanthracene-9,10-dione is 47052-29-9; the CAS number of 4,4'-tetraphenylsilanedicarboxylic acid is 18708-43-5.

[0028] The preparation method of flame-retardant filler includes the following steps: B1. Take 1.7g of 5,5-dimethyl-1,3-di(epoxyethylenemethyl)imidazolidine-2,4-dione and add it to 50ml of dimethyl sulfoxide. After stirring evenly, add 1.2g of pyridine-2,4-diol and 0.2g of triphenylphosphine. Heat to 130℃ and stir continuously for 10h. After the reaction is completed, remove the solvent, wash and dry to obtain the nitrogen-containing polymer. B2. Take 4.2g of nitrogen-containing polymer and add it to 50ml of N,N-dimethylformamide. Stir until completely dissolved, add 0.3g of 3-hydroxyphenylphosphonopropionic acid and 0.2g of p-toluenesulfonic acid, heat to 70℃, and stir at this temperature for 8h. After the reaction is completed, remove the solvent, wash and dry to obtain the flame-retardant filler.

[0029] Example 2

[0030] An insulating composite material for electrical wires comprises the following raw materials in parts by weight: 55 parts polypropylene, 20 parts compatibilizer, 2 parts antioxidant, 4 parts insulating modified filler, and 7 parts flame retardant filler; The preparation method of the insulating composite material includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, insulating modified filler, and flame retardant filler to a mixer and stir evenly at a speed of 500 r / min to obtain a premix. Step 2: Add the premixed material to the internal mixer and mix at a speed of 50 r / min for 18 min. Then feed it into the twin-screw extruder at a speed of 60 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

[0031] The preparation methods for the insulating modified filler and the flame retardant filler are the same as in Example 1.

[0032] Example 3

[0033] An insulating composite material for electrical wires comprises the following raw materials in parts by weight: 80 parts polypropylene, 20 parts compatibilizer, 3 parts antioxidant, 5 parts insulating modified filler, and 9 parts flame retardant filler; The preparation method of the insulating composite material includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, insulating modified filler, and flame retardant filler to a mixer and stir evenly at a speed of 600 r / min to obtain a premix. Step 2: Add the premixed material to the internal mixer and mix at a speed of 60 r / min for 20 min. Then feed it into the twin-screw extruder at a speed of 80 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

[0034] The preparation methods for the insulating modified filler and the flame retardant filler are the same as in Example 1.

[0035] Comparative Example 1

[0036] An insulating composite material for electrical wires comprises the following raw materials in parts by weight: 55 parts polypropylene, 20 parts compatibilizer, 2 parts antioxidant, 4 parts boehmite, 7 parts flame retardant filler; The preparation method of the insulating composite material includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, boehmite, and flame retardant filler to a mixer and stir evenly at a speed of 500 r / min to obtain a premix. Step 2: Add the premixed material to the internal mixer and mix at a speed of 50 r / min for 18 min. Then feed it into the twin-screw extruder at a speed of 60 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

[0037] The insulating modified filler was replaced with boehmite, while the rest remained the same.

[0038] Comparative Example 2

[0039] An insulating composite material for electrical wires comprises the following raw materials in parts by weight: 55 parts polypropylene, 20 parts compatibilizer, 2 parts antioxidant, 7 parts flame retardant filler; The preparation method of the insulating composite material includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, and flame retardant filler to a mixer and stir evenly at a speed of 500 r / min to obtain a premix. Step 2: Add the premixed material to the internal mixer and mix at a speed of 50 r / min for 18 min. Then feed it into the twin-screw extruder at a speed of 60 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

[0040] The preparation method of the flame retardant filler is the same as that in Example 1.

[0041] Comparative Example 3

[0042] An insulating composite material for electrical wires comprises the following raw materials in parts by weight: 55 parts polypropylene, 20 parts compatibilizer, 2 parts antioxidant, 4 parts insulating modified filler; The preparation method of the insulating composite material includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, and insulating modified filler to a mixer and stir evenly at a speed of 500 r / min to obtain a premix. Step 2: Add the premixed material to the internal mixer and mix at a speed of 50 r / min for 18 min. Then feed it into the twin-screw extruder at a speed of 60 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

[0043] The preparation method of the insulating modified filler is the same as that in Example 1.

[0044] Performance testing

[0045] The insulating composite materials from Examples 1-3 and Comparative Examples 1-3 of this invention were prepared into test samples that met the various tests.

[0046] Insulation performance testing was conducted according to standard GB / T 1408.1-2016 "Test Methods for Electrical Strength of Insulating Materials - Part 1: Tests at Power Frequency", with a test sample thickness of 0.3 mm. Flame retardant performance testing was conducted according to standard GB / T 2406.2-2009 "Determination of flammability of plastics by oxygen index method - Part 2: Room temperature test".

[0047] The results are shown in the table below:

[0048] The breakdown voltage data shows that the insulation-modified filler effectively improves the insulation properties of the insulating composite material. This is because the insulation-modified filler has a rigid structure, which can enhance the intrinsic strength and thermodynamic stability of the matrix and restrict the orientation, polarization, and displacement of the polymer molecular chains under the action of an electric field, thereby increasing the intrinsic breakdown field strength of the matrix. At the same time, the boehmite is uniformly dispersed in the polypropylene matrix, which plays a role in optimizing the electric field distribution and constructing a microscopic barrier. As can be seen from Comparative Example 1, since the boehmite cannot be uniformly dispersed in the matrix, it does not significantly improve the insulation performance.

[0049] According to the oxygen index data, flame-retardant fillers significantly improve the flame retardancy of insulating composite materials. This is because flame-retardant fillers contain nitrogen and phosphorus elements. When combustion occurs, the flame-retardant fillers produce phosphoric acid when heated, which transforms the originally flammable polypropylene molecular chains into carbon-rich, non-volatile carbonaceous residues, forming a molten carbon layer. This provides the material basis for the subsequent formation of an expanded carbon layer. At the same time, nitrogen gas is generated. Driven by a large amount of gas inside, the molten carbon layer expands rapidly, forming a dense and solid expanded carbon layer, which plays a role in heat insulation and oxygen isolation, preventing further combustion.

[0050] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. An insulating composite material for electrical wires, characterized in that, Including the following parts by weight of raw materials: 50-80 parts polypropylene, 10-20 parts compatibilizer, 1-3 parts antioxidant, 2-5 parts insulating modified filler, 5-9 parts flame retardant filler.

2. The insulating composite material for electrical wires according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene; the antioxidant is antioxidant 1010 or antioxidant 1076.

3. The insulating composite material for electrical wires according to claim 1, characterized in that, The preparation method of the insulating modified filler includes the following steps: A1. Add boehmite to deionized water and ultrasonically disperse it evenly to obtain a boehmite dispersion. Add diacid linker and acid catalyst to the boehmite dispersion, stir and heat to 70-80℃, keep warm and stir for 10-12 hours. After the reaction is completed, filter, wash and dry to obtain modified boehmite. A2. Add modified boehmite to N,N-dimethylformamide and ultrasonically disperse to obtain a modified boehmite dispersion. Add 2,3,6,7-tetraaminoanthracene-9,10-dione to the modified boehmite dispersion, heat to 80-90℃, stir for 1-2 hours, then add 4,4'-tetraphenylsilanedicarboxylic acid, continue stirring at this temperature for 8-12 hours, then heat to 120-140℃ and stir for 5-10 hours. After the reaction is complete, filter, wash, and dry to obtain the insulating modified filler.

4. The insulating composite material for electrical wires according to claim 3, characterized in that, In A1, the acidic catalyst is p-toluenesulfonic acid or aminosulfonic acid.

5. The insulating composite material for electrical wires according to claim 3, characterized in that, In A1, the diacid linker is succinic acid or glutaric acid.

6. The insulating composite material for electrical wires according to claim 3, characterized in that, In A2, the mass ratio of 4,4'-tetraphenylsilanedicarboxylic acid and 2,3,6,7-tetraaminoanthracene-9,10-dione is 1:0.8-0.

9.

7. The insulating composite material for electrical wires according to claim 1, characterized in that, The preparation method of the flame-retardant filler includes the following steps: B1. Take 5,5-dimethyl-1,3-di(epoxyethylenemethyl)imidazolidine-2,4-dione and add it to dimethyl sulfoxide. After stirring evenly, add pyridine-2,4-diol and accelerator, heat to 130-140℃, and continue stirring for 6-10 hours. After the reaction is completed, remove the solvent, wash, and dry to obtain the nitrogen-containing polymer. B2. Take the nitrogen-containing polymer and add it to N,N-dimethylformamide. Stir until completely dissolved, add 3-hydroxyphenylphosphonopropionic acid and p-toluenesulfonic acid, heat to 60-70℃, and stir at this temperature for 8-12 hours. After the reaction is completed, remove the solvent, wash and dry to obtain the flame-retardant filler.

8. The insulating composite material for electrical wires according to claim 7, characterized in that, In B1, the accelerator is triphenylphosphine.

9. The insulating composite material for electrical wires according to claim 7, characterized in that, In B1, the mass ratio of 5,5-dimethyl-1,3-di(epoxyethylenemethyl)imidazolidine-2,4-dione and pyridine-2,4-diol is 1:0.45-0.

73.

10. A method for preparing an insulating composite material for electrical wires as described in claim 1, characterized in that, Includes the following steps: Step 1: Add polypropylene, compatibilizer, antioxidant, insulating modified filler, and flame retardant filler to a mixer and stir evenly at a speed of 400-600 r / min to obtain a premix. Step 2: Add the premixed material to a mixer and mix at a speed of 40-60 r / min for 15-20 min. Then feed it into a twin-screw extruder at a speed of 40-80 r / min. Set the extruder temperature as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 220-230℃, Zone 5 200-220℃. Extrude to obtain the insulating composite material.

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