Flame resistant polyethylene wire and cable and method of production

Abstract

The application relates to the technical field of cables, and discloses a flame-resistant polyethylene wire cable and a production method thereof. The wire cable comprises a metal conductor and polyethylene cable material coated on the outer side of the metal conductor. The polyethylene cable material is prepared by mixing and extruding high-density polyethylene and low-density polyethylene as main raw materials and organic-inorganic composite flame retardants and other additives. The prepared organic-inorganic composite flame retardant is palygorskite coated with phosphorus-containing polymeric macromolecular substances on the surface. The organic phosphorus-containing polymeric macromolecular substances can form a transition connection structure between the palygorskite and the polyethylene matrix. The transition structure can greatly improve the compatibility between the palygorskite and the polyethylene matrix, so that the palygorskite and the polyethylene matrix can be uniformly dispersed with each other. Furthermore, the mechanical strength and the flame resistance of the polyethylene can be improved by utilizing the reinforcing effect of the organic-inorganic composite flame retardant.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a flame-resistant polyethylene wire and cable and its production method. Background Technology

[0002] As indispensable basic materials in modern power and communication networks, the quality and performance of wires and cables directly affect the safe and stable operation of the entire system. Polyethylene (PE), a lightweight, non-toxic thermoplastic with excellent electrical insulation and chemical corrosion resistance, is often used as the sheathing material for wires and cables and is widely used in the wire and cable industry. However, the flammability of polyethylene is a significant drawback, especially under conditions of high voltage, heat, and discharge. Polyethylene wires and cables are easily ignited, causing fires and threatening people's lives and property, posing a significant safety hazard. Therefore, flame-retardant modification of polyethylene wires and cables is particularly important.

[0003] Currently, the main methods for flame-retardant modification of polyethylene include the following: First, by adding inorganic flame retardants, such as magnesium hydroxide. However, these flame retardants have limited flame-retardant modification effects, so a large amount is generally required to achieve a certain effect. However, increasing the amount added also affects the mechanical strength and other properties of polyethylene. Second, by adding halogenated or phosphorus-based flame retardants, the flame retardancy of polyethylene can also be improved. However, halogenated flame retardants are not environmentally friendly and generate toxic gases during combustion, posing a significant safety hazard. Conventional phosphorus-based flame retardants are prone to volatilization and migration, making it difficult to guarantee the long-term flame retardancy of polyethylene. In summary, existing technologies for flame-retardant modification of polyethylene all have certain shortcomings. Based on this, the present invention provides a flame-retardant polyethylene that can be used as a sheathing material for wires and cables and exhibits excellent flame-retardant properties. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a flame-retardant polyethylene wire and cable and its production method.

[0006] (II) Technical Solution

[0007] A flame-retardant polyethylene wire and cable includes a metal conductor and a polyethylene cable material covering the outside of the metal conductor; the polyethylene cable material comprises the following raw materials in parts by weight:

[0008]

[0009] The organic-inorganic composite flame retardant is palygorskite with phosphorus-containing polymeric macromolecules coated on its surface.

[0010] As a further aspect of the present invention, the compatibilizer is maleic anhydride-grafted polyethylene or maleic anhydride-grafted polypropylene.

[0011] As a further aspect of the present invention, the preparation method of the organic-inorganic composite flame retardant includes the following steps:

[0012] Step 1: Surface modification of palygorskite is performed using an epoxy silane coupling agent to obtain modified palygorskite;

[0013] Step 2: Using toluene as the dispersion medium, and employing a phase transfer catalyst, the modified palygorskite is further grafted with phosphorus-containing polymeric macromolecules to obtain an organic-inorganic composite flame retardant.

[0014] As a further aspect of the present invention, in step one, the epoxy silane coupling agent is γ-glycidoxypropyltrimethoxysilane or γ-glycidoxypropyltriethoxysilane.

[0015] As a further embodiment of the present invention, in step two, the phase transfer catalyst is any one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, tetramethylammonium bromide, or tetrabutylammonium chloride.

[0016] As a further aspect of the present invention, in step two, the specific preparation method of the phosphorus-containing polymeric macromolecule includes the following steps:

[0017] Step S1: Nitrogen gas is introduced into the reaction vessel. Then, malic acid, 2-chloro-2-oxo-1,3,2-dioxophosphazenecyclopentane and tetrahydrofuran solvent are added to the reaction vessel. Stirring is started. After a homogeneous reaction solution is formed, an alkaline catalyst is added to the reaction solution. After the addition is complete, heating is started and the temperature is raised to 60-65°C. The mixture is kept at this temperature and stirred for 4-8 hours. The solvent is evaporated and removed. The product is collected after cooling to obtain the malic acid derivative.

[0018] Step S2: Add malic acid derivative and N,N-dimethylformamide to the polymerization reactor and stir until well mixed. Then add 2,6-pyridinediethanol to the polymerization reactor and p-toluenesulfonic acid under nitrogen protection. After the addition is complete, control the heating rate to 2-4℃ / min and raise the temperature to 120-150℃. Hold the temperature for 12-24 hours, cool down and discharge the material to obtain phosphorus-containing polymerized macromolecules.

[0019] As a further aspect of the present invention, in step S1, the alkaline catalyst is triethylamine or pyridine.

[0020] As a further aspect of the present invention, in step S2, the molar ratio of the malic acid derivative and 2,6-pyridinediethanol is 1:0.8-1.

[0021] In the above technical solution, malic acid and 2-chloro-2-oxo-1,3,2-dioxophosphoric acid cyclopentane are first used as reactants. Under the catalysis of an alkaline catalyst, the active hydroxyl substituents and P-Cl react to obtain a malic acid derivative containing phosphorus flame retardant in its structure. Since its structure contains two equivalents of active carboxyl substituents, it can undergo a continuous condensation reaction with the active hydroxyl substituents in the structure of 2,6-pyridinediethanol under the action of high temperature and p-toluenesulfonic acid to form a large alternating polymer linked by ester bonds, that is, a phosphorus-containing polymeric macromolecule.

[0022] Next, under the action of a phase transfer catalyst, phosphorus-containing polymeric macromolecules are used to further modify the surface of epoxidized palygorskite, forming palygorskite with phosphorus-containing polymeric macromolecules on its surface, i.e., an organic-inorganic composite flame retardant.

[0023] As a further embodiment of the present invention, the rubber-type additive is at least one of EPDM rubber, nitrile rubber, or polybutadiene rubber; the antioxidant is antioxidant 1010 or antioxidant 168; the lubricant is at least one of polyethylene wax, stearic acid, or paraffin wax; and the inorganic filler is at least one of titanium dioxide, calcium titanate, talc, or fumed silica.

[0024] A method for producing flame-retardant polyethylene wires and cables includes the following steps:

[0025] Step 1: Preparation of Polyethylene Cable Material

[0026] Weigh and mix all the raw materials according to the specified weight proportions, then add them to the mixer. After mechanically mixing them evenly at a temperature of 80-100℃, feed them into a twin-screw extruder for melt extrusion to form polyethylene cable material.

[0027] Step 2: Preparation of polyethylene wires and cables

[0028] Polyethylene cable is produced by extruding polyethylene cable material onto the surface of a metal conductor, followed by cooling, winding, and packaging.

[0029] (III) Beneficial Technical Effects

[0030] The organic-inorganic composite flame retardant prepared in this invention is palygorskite coated with phosphorus-containing polymeric macromolecules. Firstly, the presence of these organic phosphorus-containing polymeric macromolecules forms a "transitional" connecting structure between the palygorskite and the polyethylene matrix. This transitional structure significantly improves the compatibility between the palygorskite and the polyethylene matrix, enabling them to disperse evenly. This allows the palygorskite to act as an inorganic modifier, enhancing the mechanical strength of the polyethylene. Secondly, the phosphorus-containing polymeric macromolecules contain a large amount of alternating nitrogen and phosphorus flame-retardant elements. These elements rapidly form an expanding carbon layer during combustion, isolating oxygen and heat, thus effectively improving the flame resistance of polyethylene. Furthermore, as a magnesium-aluminum-rich mineral, palygorskite itself produces oxide layers such as magnesium oxide and aluminum oxide in high-temperature environments. These oxides have high melting points and good thermal stability, exhibiting certain flame-retardant properties. These oxides synergistically enhance the flame resistance of polyethylene with the phosphorus-containing polymeric macromolecules. Attached Figure Description

[0031] 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.

[0032] Figure 1 Infrared spectral analysis of phosphorus-containing polymeric macromolecules. Detailed Implementation

[0033] 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.

[0034] Preparation Example

[0035] Preparation of organic-inorganic composite flame retardants:

[0036] Step 1: Disperse 3.5g of palygorskite in an ultrasonically dispersed 70% ethanol solution. Then add 5g of γ-glycidoxypropyltrimethoxysilane to the resulting dispersion. After the addition is complete, raise the temperature to 70℃ and keep it at that temperature for 8 hours. Separate the solid material to obtain modified palygorskite.

[0037] Step 2: Add 2.6g of modified palygorskite to toluene solvent and disperse for 40min to form a uniform dispersion. Then add 1.5g of phosphorus-containing polymeric macromolecule and 0.1g of tetrabutylammonium bromide to the dispersion, stir mechanically, and keep it at 75℃ for 9h. Separate the solid material to obtain the organic-inorganic composite flame retardant.

[0038] The preparation method of phosphorus-containing polymeric macromolecules includes the following steps:

[0039] Step S1: Nitrogen gas is introduced into the reaction vessel. Then, 0.8g of malic acid, 0.85g of 2-chloro-2-oxo-1,3,2-dioxophosphazenecyclopentane and tetrahydrofuran solvent are added to the reaction vessel. Stirring is started. After a homogeneous reaction solution is formed, 0.1g of triethylamine is added to the reaction solution. After the addition is complete, heating is started and the temperature is raised to 65°C. The mixture is kept at this temperature and stirred for 6 hours. The solvent is evaporated and removed. The product is collected after cooling to obtain the malic acid derivative.

[0040] Step S2: Add 1.2g of malic acid derivative and N,N-dimethylformamide to the polymerization reactor and stir to mix well. Then add 0.6g of 2,6-pyridinediethanol to the polymerization reactor, purge with nitrogen for protection, and add p-toluenesulfonic acid at the same time. After the addition is complete, control the heating rate to 3℃ / min and raise the temperature to 150℃. Keep it at this temperature for 18h, cool it down and discharge the material to obtain the phosphorus-containing polymerized macromolecular substance.

[0041] Figure 1 This is the infrared analysis spectrum of the phosphorus-containing polymeric macromolecule, with the 3000–3100 cm⁻¹ range shown. -1 The characteristic absorption peak appearing at 1700–1800 cm⁻¹ is the CH absorption peak in the pyridine ring. -1 The characteristic absorption peak appearing at 1264 cm⁻¹ is the characteristic absorption peak of C=O in ester and carboxyl groups. -1 The characteristic absorption peak appearing at this point is the characteristic absorption peak of PO.

[0042] Example 1

[0043] Preparation of polyethylene cable material

[0044] According to the weight percentages, 55 parts high-density polyethylene, 15 parts low-density polyethylene, 5 parts maleic anhydride grafted polyethylene, 2 parts organic-inorganic composite flame retardant, 5 parts EPDM rubber, 0.5 parts antioxidant 1010, 1 part lubricant polyethylene wax, and 3 parts inorganic filler titanium dioxide are weighed and mixed in a mixer. After being mechanically stirred evenly at 80°C, the mixture is fed into a twin-screw extruder. The temperature is controlled at 240°C and the screw speed is 50 rpm. After melt extrusion, polyethylene cable material is formed.

[0045] The preparation method of the organic-inorganic composite flame retardant is shown in the preparation example, and the same applies to the following.

[0046] Example 2

[0047] Preparation of polyethylene cable material

[0048] According to the weight percentages, 58 parts high-density polyethylene, 18 parts low-density polyethylene, 5 parts maleic anhydride grafted polypropylene, 5 parts organic-inorganic composite flame retardant, 10 parts nitrile rubber, 0.6 parts antioxidant 168, 1.5 parts lubricant paraffin wax, and 5 parts inorganic filler talc are weighed and mixed. Then, they are added to a mixer and mechanically stirred evenly at 100°C. The mixture is then fed into a twin-screw extruder, where the temperature is controlled at 240°C and the screw speed is 50 rpm. After melt extrusion, polyethylene cable material is formed.

[0049] Example 3

[0050] Preparation of polyethylene cable material

[0051] According to the weight percentages, 65 parts high-density polyethylene, 25 parts low-density polyethylene, 10 parts maleic anhydride-grafted polypropylene, 5.5 parts organic-inorganic composite flame retardant, 15 parts polybutadiene rubber, 1.5 parts antioxidant 168, 2 parts lubricant paraffin wax, and 6 parts inorganic filler fumed silica are weighed and mixed. Then, they are added to a mixer and mechanically stirred evenly at 100°C. The mixture is then fed into a twin-screw extruder, where the temperature is controlled at 240°C and the screw speed is 50 rpm. After melt extrusion, polyethylene cable material is formed.

[0052] Comparative Example 1

[0053] Preparation of polyethylene cable material

[0054] According to the weight percentages, 58 parts high-density polyethylene, 18 parts low-density polyethylene, 5 parts maleic anhydride-grafted polypropylene, 5 parts palygorskite, 10 parts nitrile rubber, 0.6 parts antioxidant 168, 1.5 parts lubricant paraffin wax, and 5 parts inorganic filler talc are weighed and mixed. Then, they are added to a mixer and mechanically stirred evenly at 100°C. The mixture is then fed into a twin-screw extruder, where the temperature is controlled at 240°C and the screw speed is 50 rpm. After melt extrusion, polyethylene cable material is formed.

[0055] Comparative Example 2

[0056] Preparation of polyethylene cable material

[0057] According to the weight percentages, 58 parts high-density polyethylene, 18 parts low-density polyethylene, 5 parts maleic anhydride-grafted polypropylene, 5 parts phosphorus-containing polymeric macromolecules, 10 parts nitrile rubber, 0.6 parts antioxidant 168, 1.5 parts lubricant paraffin wax, and 5 parts inorganic filler talc are weighed and mixed in a mixer. After being mechanically stirred evenly at 100°C, the mixture is fed into a twin-screw extruder. The temperature is controlled at 240°C and the screw speed is 50 rpm. After melt extrusion, polyethylene cable material is formed.

[0058] The preparation method for phosphorus-containing polymeric macromolecules is shown in the preparation examples.

[0059] Comparative Example 3

[0060] Preparation of polyethylene cable material

[0061] According to the weight percentages, 58 parts high-density polyethylene, 18 parts low-density polyethylene, 5 parts maleic anhydride-grafted polypropylene, 10 parts nitrile rubber, 0.6 parts antioxidant 168, 1.5 parts lubricant paraffin wax, and 5 parts inorganic filler talc powder are weighed and mixed in a mixer. After being mechanically stirred evenly at 100°C, the mixture is fed into a twin-screw extruder. The temperature is controlled at 240°C and the screw speed is 50 rpm. After melt extrusion, polyethylene cable material is formed.

[0062] Test case

[0063] The polyethylene cable materials used in the examples and comparative examples were made into various test samples, and performance tests were conducted. The results are recorded in Table 1:

[0064] Table 1 - Performance Test Results

[0065] Tensile strength / MPa Limiting oxygen index / % Example 1 45.1 31.3 Example 2 45.3 31.6 Example 3 45.1 31.4 Comparative Example 1 39.4 23.9 Comparative Example 2 30.6 29.8 Comparative Example 3 29.8 18.2

[0066] The tensile strength test reference standard is GB / T 1040-2008; the limiting oxygen index test reference standard is GB / T2406-2009.

[0067] Analysis shows that the polyethylene cable material prepared using the organic-inorganic composite flame retardant as an additive in the preparation example of this invention has significantly better mechanical strength and excellent flame retardant properties. Replacing the organic-inorganic composite flame retardant with unmodified palygorskite results in a decrease in mechanical strength due to interfacial issues between the palygorskite and the matrix, preventing the full exertion of its reinforcing and modifying effects. Replacing the organic-inorganic composite flame retardant with a phosphorus-containing polymeric macromolecule eliminates the reinforcing and flame-retardant effects of palygorskite, leading to a decline in both the mechanical and flame-retardant properties of the polyethylene cable material.

[0068] The specific preparation method for a flame-resistant polyethylene wire and cable using the polyethylene cable material in Example 2 of this invention is as follows:

[0069] Polyethylene cable is produced by extruding polyethylene cable material onto the surface of a metal conductor, followed by cooling, winding, and packaging.

[0070] 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 flame-retardant polyethylene wire and cable, characterized in that, The cable material comprises a metal conductor and a polyethylene cable covering the outside of the metal conductor; the polyethylene cable material comprises the following raw materials in parts by weight: 55-65 parts of high-density polyethylene; 15-25 parts of low-density polyethylene; 5-10 parts compatibilizer; 2-5.5 parts of organic-inorganic composite flame retardant; 5-15 parts of rubber-based additives; Antioxidant 0.5-1.5 parts; 1-2 parts lubricant; 3-6 parts of inorganic filler; The organic-inorganic composite flame retardant is palygorskite with phosphorus-containing polymeric macromolecules coated on its surface; The preparation method of the organic-inorganic composite flame retardant includes the following steps: Step 1: Surface modification of palygorskite is performed using an epoxy silane coupling agent to obtain modified palygorskite; Step 2: Using toluene as the dispersion medium, and employing a phase transfer catalyst, the modified palygorskite is further grafted with phosphorus-containing polymeric macromolecules to obtain an organic-inorganic composite flame retardant. The specific preparation method of the phosphorus-containing polymeric macromolecule includes the following steps: Step S1: Nitrogen gas is introduced into the reaction vessel. Then, malic acid, 2-chloro-2-oxo-1,3,2-dioxophosphazenecyclopentane and tetrahydrofuran solvent are added to the reaction vessel. Stirring is started. After a homogeneous reaction solution is formed, an alkaline catalyst is added to the reaction solution. After the addition is complete, heating is started and the temperature is raised to 60-65°C. The mixture is kept at this temperature and stirred for 4-8 hours. The solvent is evaporated and removed. The product is collected after cooling to obtain the malic acid derivative. Step S2: Add malic acid derivative and N,N-dimethylformamide to the polymerization reactor and stir until well mixed. Then add 2,6-pyridinediethanol to the polymerization reactor and p-toluenesulfonic acid under nitrogen protection. After the addition is complete, control the heating rate to 2-4℃ / min and raise the temperature to 120-150℃. Hold the temperature for 12-24 hours, cool down and discharge the material to obtain phosphorus-containing polymerized macromolecules.

2. The flame-retardant polyethylene wire and cable according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polyethylene or maleic anhydride-grafted polypropylene.

3. The flame-retardant polyethylene wire and cable according to claim 1, characterized in that, In step one, the epoxy silane coupling agent is γ-glycidoxypropyltrimethoxysilane or γ-glycidoxypropyltriethoxysilane.

4. The flame-retardant polyethylene wire and cable according to claim 1, characterized in that, In step two, the phase transfer catalyst is any one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, tetramethylammonium bromide, or tetrabutylammonium chloride.

5. The flame-retardant polyethylene wire and cable according to claim 1, characterized in that, In step S1, the alkaline catalyst is triethylamine or pyridine.

6. The flame-retardant polyethylene wire and cable according to claim 1, characterized in that, In step S2, the molar ratio of the malic acid derivative and 2,6-pyridinediethanol is 1:0.8-1.

7. The flame-retardant polyethylene wire and cable according to claim 1, characterized in that, The rubber-type additive is at least one of EPDM rubber, nitrile rubber, or polybutadiene rubber; the antioxidant is antioxidant 1010 or antioxidant 168; the lubricant is at least one of polyethylene wax, stearic acid, or paraffin wax; and the inorganic filler is at least one of titanium dioxide, calcium titanate, talc, or fumed silica.

8. A method for producing flame-retardant polyethylene wires and cables as described in claim 1, characterized in that, Includes the following steps: Step 1: Preparation of Polyethylene Cable Material Weigh and mix all the raw materials according to the specified weight proportions, then add them to the mixer. After mechanically mixing them evenly at a temperature of 80-100℃, feed them into a twin-screw extruder for melt extrusion to form polyethylene cable material. Step 2: Preparation of polyethylene wires and cables Polyethylene cable is produced by extruding polyethylene cable material onto the surface of a metal conductor, followed by cooling, winding, and packaging.

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