A composite flame retardant for cable materials and its preparation method

Abstract

The present invention relates to the technical field of cable flame retardants, and specifically discloses a composite flame retardant for cable materials and a preparation method thereof. The raw materials of the above-mentioned composite flame retardant for cable materials include, by mass: 10-20 parts of palygorskite clay, 1-2 parts of γ-aminopropyltriethoxysilane, 1.01-3.1 parts of sodium methoxide, 1-5 parts of ethylenediamine, 5-10 parts of methyl acrylate, 1.5-6 parts of glyoxylic acid, 1-2 parts of potassium ethoxide, and 5-15 parts of hexagonal boron nitride. The composite flame retardant for cable materials obtained by the present invention not only has excellent flame retardant and heat conduction properties, but also can ensure the mechanical strength of the product when applied to cable materials. When it is applied to polyethylene-based cable materials and irradiated and crosslinked by electron beam after melting and plasticization, it effectively promotes the regular arrangement of boron nitride, not only quickly promotes the rapid transmission of heat and reduces the possibility of heat concentration, but also has a high bonding strength with polyethylene and further enhances the durability.

Description

Technical Field

[0001] The invention relates to the technical field of cable flame retardants, and in particular to a composite flame retardant for cable materials and a preparation method thereof. Background Art

[0002] Plastics used for insulation and sheathing of wires and cables are commonly known as cable materials, which are mainly composed of polymer base materials and additives. For polymers that can be used in the field of wires and cables, they are not only required to have good electrical insulation properties and good processing properties, but also good flame retardant properties. Flame retardant wires and cables can greatly reduce casualties and property losses caused by fires caused by wires and cables.

[0003] Polyethylene has the advantages of good electrical insulation, small dielectric constant, low dielectric loss and excellent chemical stability, and is one of the widely used polymer base materials in cable materials. However, polyethylene has poor flame retardancy and thermal conductivity, with an oxygen index of only 17.4 and a thermal conductivity of only 0.3-0.5W / (m·K). Therefore, it is very easy to burn under uneven heating or external environmental influences, and is not easy to extinguish, posing a huge threat to people's life safety, resulting in limited development in the field of cable materials.

[0004] The flame retardancy of cable materials is very important. Therefore, the research and development of high thermal conductivity flame retardants for polyethylene has a significant role in promoting the development of the wire and cable industry.

[0005] Palygorskite clay is a natural hydrated magnesium aluminum silicate mineral with a special rod-shaped and needle-shaped crystal structure. Palygorskite clay has excellent decolorization, adsorption, ion exchange, thermal stability, salt resistance, gelation and high-temperature phase change properties. It has a wide range of uses and can be widely used in petroleum, chemical industry, building materials, papermaking, medicine, agriculture, ecological environment protection, leather making, feed, fertilizer, food, automobile and military industry. The application of palygorskite clay in flame retardant materials has received widespread attention in recent years. The compound of palygorskite clay and boron nitride flame retardant has excellent flame retardant properties, but the addition amount is limited. If a large amount is added, it can improve the flame retardancy of the material, but it will cause the mechanical properties of polyethylene cable materials to be significantly reduced, which needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a composite flame retardant for cable materials and a preparation method thereof.

[0007] A composite flame retardant for cable materials. The raw materials thereof include, by mass, 10-20 parts of palygorskite clay, 1-2 parts of gamma-aminopropyltriethoxysilane, 1.01-3.1 parts of sodium methoxide, 1-5 parts of ethylenediamine, 5-10 parts of methyl acrylate, 1.5-6 parts of glyoxylic acid, 1-2 parts of potassium ethoxide and 5-15 parts of hexagonal boron nitride.

[0008] Preferably, the particle size of hexagonal boron nitride is 100 - 300 nm.

[0009] The preparation method of the above-mentioned composite flame retardant for cable materials comprises the following steps:

[0010] S1. Add palygorskite clay to deionized water, stir for 10 - 20 min, perform ultrasonic crushing treatment for 1 - 4 h, add γ-aminopropyltriethoxysilane, stir at 85 - 95 °C for 1 - 2 h, cool to room temperature, filter by suction, and dry in vacuum to obtain pretreated clay;

[0011] S2. Add the pretreated clay to methanol and stir evenly, add potassium methoxide and stir evenly. Under nitrogen protection, successively add ethylenediamine and methyl acrylate thereto, stir at 10 - 20 °C for 20 - 30 h under nitrogen protection, raise the temperature to 30 - 40 °C and stir for 5 - 15 h, remove nitrogen protection, add glyoxylic acid solution, stir at 10 - 20 °C for 1 - 2 h, centrifuge, wash, and dry in vacuum to obtain activated clay;

[0012] S3. Mix sodium methoxide and potassium ethoxide by grinding evenly, add hexagonal boron nitride thereto, stir and react at 180 - 190 °C for 1 - 2 h, cool to room temperature, wash, dry, and add to the activated clay into an ethanol aqueous solution, reflux and stir at 100 - 120 °C for 1 - 2 h, cool to room temperature, centrifuge, and dry in vacuum.

[0013] Preferably, in S1, the power of the ultrasonic crushing treatment is 800 - 1000 W.

[0014] Preferably, in S2, the mass fraction of the glyoxylic acid solution is 30 - 40%.

[0015] Preferably, the mass ratio of the potassium methoxide used in S2 to the potassium methoxide used in S3 is 0.01 - 0.1:1 - 3.

[0016] Preferably, in S3, the mass fraction of the ethanol aqueous solution is 50 - 70%.

[0017] A flame-retardant cable material, the raw materials thereof comprising: the above-mentioned composite flame retardant for cable materials, polyethylene.

[0018] Preferably, the raw materials of the above-mentioned flame-retardant cable material by mass parts comprise: 100 parts of polyethylene, 1 - 3 parts of a toughening agent, and 20 - 30 parts of the above-mentioned composite flame retardant for cable materials.

[0019] The preparation method of the above-mentioned flame-retardant cable material comprises the following steps: Mix polyethylene, a toughening agent, and the above-mentioned composite flame retardant for cable materials evenly, open mill at 130 - 150 °C for 1 - 5 min, melt, plasticize at 190 - 210 °C for 1 - 5 min, the plasticizing pressure is 20 - 30 MPa, and perform electron beam irradiation crosslinking, the irradiation dose is 150 - 160 kGy. Beneficial Effects

[0020] If the palygorskite clay is directly added to the polyethylene matrix, the dispersibility is poor. In the present invention, the palygorskite clay is pretreated and then combined with a hyperbranched polyamide amine on its surface, which not only greatly enhances the dispersibility of the palygorskite clay in the polyethylene matrix, but also the end is carboxylated by glyoxylic acid treatment, and the hyperbranched polyamide amine has a unique cavity structure and a three-dimensional structure, which is more conducive to the isotropic uniformity of the palygorskite clay in the polyethylene matrix. In addition, the palygorskite clay can overlap in the polyethylene matrix to form a skeleton and promote the formation of a new network, thereby significantly improving the mechanical properties and flame retardant properties of the polyethylene matrix and improving the durability of the cable material.

[0021] The present invention uses hexagonal boron nitride to undergo hydroxylation treatment, which can effectively increase the reactivity between hexagonal boron nitride and activated clay. The activated clay obtained in the present invention has a large number of carboxyl groups on its surface, which can be combined with the hydroxyl groups on the surface of boron nitride. Not only is the bonding strength high, but also the boron nitride can be evenly combined with the palygorskite clay structure due to its special flaky hexagonal structure. The two work synergistically, improving flame retardancy while also having excellent thermal conductivity.

[0022] The composite flame retardant obtained by the present invention is applied to polyethylene-based cable materials. After being melt-plasticized and then cross-linked by electron beam irradiation, the regular arrangement of boron nitride is effectively promoted, which not only promotes rapid heat transmission and reduces the possibility of heat concentration, but also has high bonding strength with polyethylene, further enhances durability, and effectively prolongs the service life of the cable material.

[0023] The composite flame retardant for cable material obtained by the present invention not only has excellent flame retardancy and thermal conductivity, but also can ensure the mechanical strength of the product when applied to the cable material. At the same time, the method and the required equipment of the present invention are simple, the raw materials and intermediates are inexpensive, and the implementation is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the thermogravimetric analysis curve of the flame retardant cable material obtained in Example 5.

[0025] Figure 2 It is a comparison chart of the tensile strength and elongation at break of the flame retardant cable materials obtained in Example 5 and Comparative Examples 1-2.

[0026] Figure 3 This is a comparison chart of the retention rate of tensile properties of the flame-retardant cable materials obtained in Example 5 and Comparative Examples 1-2 after heat aging (150°C×72h).

[0027] Figure 4 It is a comparison chart of thermal conductivity and oxygen index of the flame retardant cable materials obtained in Example 5 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments.

[0029] The polyolefin thermoplastic elastomer (POE) used below is from ExxonMobil in the United States, with the grade of VM6202.

[0030] Example 1

[0031] A composite flame retardant for cable materials, the raw materials of which include: 1000 g of palygorskite clay, 100 g of γ-aminopropyltriethoxysilane, 101 g of sodium methoxide, 100 g of ethylenediamine, 500 g of methyl acrylate, 150 g of glyoxylic acid, 100 g of potassium ethanolate, and 500 g of hexagonal boron nitride with a particle size of 100 - 300 nm.

[0032] The preparation method of the above-mentioned composite flame retardant for cable materials includes the following steps:

[0033] S1. Add palygorskite clay to 5000 g of deionized water, stir at a speed of 1000 r / min for 10 min, treat with an ultrasonic crusher for 1 h, with a treatment power of 800 W, add γ-aminopropyltriethoxysilane, stir at a temperature of 85 °C for 1 h, cool to room temperature, filter by suction, and vacuum dry to obtain pretreated clay;

[0034] S2. Add the pretreated clay to 3000 g of methanol and stir evenly, add 1 g of potassium methoxide and stir evenly. Under nitrogen protection, add ethylenediamine and methyl acrylate thereto in sequence. Stir at a temperature of 10 °C for 20 h, then raise the temperature to 30 °C and stir for 5 h. Remove nitrogen protection, add a 30% glyoxylic acid solution by mass fraction, stir at a temperature of 10 °C for 1 h, centrifuge, wash with deionized water, and vacuum dry to obtain activated clay;

[0035] S3. Mix 100 g of sodium methoxide and potassium ethanolate evenly by grinding, add hexagonal boron nitride thereto, stir and react at 180 for 1 h, cool to room temperature, wash, dry, and add it to 10000 g of an ethanol aqueous solution with a mass fraction of 50%. Reflux and stir at 100 °C for 1 h, cool to room temperature, centrifuge, and vacuum dry.

[0036] A flame retardant cable material, the raw materials of which include: 1000 g of polyethylene, 10 g of polyolefin thermoplastic elastomer, and 200 g of the above-mentioned composite flame retardant for cable materials.

[0037] The preparation method of the above-mentioned flame retardant cable material includes the following steps: Mix polyethylene, polyolefin thermoplastic elastomer, and the above-mentioned composite flame retardant for cable materials evenly, feed them into a two-roll mill, open mill at a temperature of 130 °C for 1 min to melt, plasticize and form at a temperature of 190 °C for 1 min, with a plasticizing pressure of 20 MPa, and carry out electron beam irradiation crosslinking with an irradiation dose of 150 kGy.

[0038] Example 2

[0039] A composite flame retardant for cable materials, the raw materials of which include: 2000 g of palygorskite clay, 200 g of γ-aminopropyltriethoxysilane, 310 g of sodium methoxide, 500 g of ethylenediamine, 1000 g of methyl acrylate, 600 g of glyoxylic acid, 200 g of potassium ethoxide, and 1500 g of hexagonal boron nitride with a particle size of 100 - 300 nm.

[0040] The preparation method of the above-mentioned composite flame retardant for cable materials includes the following steps:

[0041] S1. Add palygorskite clay to 15000 g of deionized water, stir at a speed of 2000 r / min for 20 min, treat with an ultrasonic crusher for 4 h, the treatment power is 1000 W, add γ-aminopropyltriethoxysilane, stir at a temperature of 95 °C for 2 h, cool to room temperature, filter by suction, and vacuum dry to obtain pretreated clay;

[0042] S2. Add the pretreated clay to 5000 g of methanol and stir evenly, add 10 g of potassium methoxide and stir evenly. Under nitrogen protection, add ethylenediamine and methyl acrylate thereto in sequence. Stir at a temperature of 20 °C for 30 h under nitrogen protection, raise the temperature to 40 °C and stir for 15 h, remove nitrogen protection, add a 40% mass fraction of glyoxylic acid solution, stir at a temperature of 20 °C for 2 h, centrifuge, wash with deionized water, and vacuum dry to obtain activated clay;

[0043] S3. Mix 300 g of sodium methoxide and potassium ethoxide evenly by grinding, add hexagonal boron nitride thereto, stir and react at 190 for 2 h, cool to room temperature, wash, dry, and add it to 15000 g of an ethanol aqueous solution with a mass fraction of 70%. Reflux and stir at 120 °C for 2 h, cool to room temperature, centrifuge, and vacuum dry.

[0044] A flame retardant cable material, the raw materials of which include: 1000 g of polyethylene, 30 g of polyolefin thermoplastic elastomer, and 300 g of the above-mentioned composite flame retardant for cable materials.

[0045] The preparation method of the above-mentioned flame retardant cable material includes the following steps: Mix polyethylene, polyolefin thermoplastic elastomer, and the above-mentioned composite flame retardant for cable materials evenly, feed them into a two-roll mill, open mill at a temperature of 150 °C for 5 min, melt, plasticize and form at a temperature of 210 °C for 5 min, the plasticizing pressure is 30 MPa, and carry out electron beam irradiation crosslinking, and the irradiation dose is 160 kGy.

[0046] Example 3

[0047] A composite flame retardant for cable materials, the raw materials of which include: 1200 g of palygorskite clay, 170 g of γ-aminopropyltriethoxysilane, 257 g of sodium methoxide, 200 g of ethylenediamine, 900 g of methyl acrylate, 200 g of glyoxylic acid, 170 g of potassium ethoxide, and 800 g of hexagonal boron nitride with a particle size of 100-300 nm.

[0048] The preparation method of the above composite flame retardant for cable materials includes the following steps:

[0049] S1. Add palygorskite clay to 12000 g of deionized water, stir at a speed of 1300 r / min for 18 min, treat with an ultrasonic crusher for 2 h, with a treatment power of 950 W, add γ-aminopropyltriethoxysilane, stir at a temperature of 88 °C for 100 min, cool to room temperature, filter by suction, and vacuum dry to obtain pretreated clay;

[0050] S2. Add the pretreated clay to 3500 g of methanol and stir evenly, add 7 g of potassium methoxide and stir evenly. Under nitrogen protection, add ethylenediamine and methyl acrylate thereto in sequence. Stir at a temperature of 12 °C for 28 h under nitrogen protection, raise the temperature to 33 °C and stir for 12 h, remove nitrogen protection, add a glyoxylic acid solution with a mass fraction of 33%, stir at a temperature of 18 °C for 80 min, centrifuge, wash with deionized water, and vacuum dry to obtain activated clay;

[0051] S3. Mix 250 g of sodium methoxide and potassium ethoxide by grinding evenly, add hexagonal boron nitride thereto, stir and react at 182 °C for 100 min, cool to room temperature, wash, dry, and add it with the activated clay to 11000 g of an ethanol aqueous solution with a mass fraction of 65%. Reflux and stir at 105 °C for 100 min, cool to room temperature, centrifuge, and vacuum dry.

[0052] A flame retardant cable material, the raw materials of which include: 1000 g of polyethylene, 15 g of polyolefin thermoplastic elastomer, and 280 g of the above composite flame retardant for cable materials.

[0053] The preparation method of the above flame retardant cable material includes the following steps: Mix polyethylene, polyolefin thermoplastic elastomer, and the above composite flame retardant for cable materials evenly, send them into a two-roll mill, open mill at a temperature of 135 °C for 4 min to melt, plasticize and form at a temperature of 195 °C for 4 min, with a plasticizing pressure of 22 MPa, and carry out electron beam irradiation crosslinking with an irradiation dose of 158 kGy.

[0054] Example 4

[0055] A composite flame retardant for cable materials, the raw materials of which include: 1800 g of palygorskite clay, 130 g of γ-aminopropyltriethoxysilane, 153 g of sodium methoxide, 400 g of ethylenediamine, 700 g of methyl acrylate, 400 g of glyoxylic acid, 130 g of potassium ethoxide, and 1200 g of hexagonal boron nitride with a particle size of 100 - 300 nm.

[0056] The preparation method of the above composite flame retardant for cable materials includes the following steps:

[0057] S1. Add palygorskite clay to 8000 g of deionized water, stir at a speed of 1700 r / min for 12 min, treat with an ultrasonic crusher for 3 h, with a treatment power of 850 W, add γ-aminopropyltriethoxysilane, stir at a temperature of 92 °C for 80 min, cool to room temperature, filter by suction, and vacuum dry to obtain pretreated clay;

[0058] S2. Add the pretreated clay to 4500 g of methanol and stir evenly, add 3 g of potassium methoxide and stir evenly. Under nitrogen protection, add ethylenediamine and methyl acrylate thereto in sequence. Stir at a temperature of 18 °C for 22 h under nitrogen protection, raise the temperature to 37 °C and stir for 8 h, remove nitrogen protection, add a 37% glyoxylic acid solution by mass fraction, stir at a temperature of 12 °C for 100 min, centrifuge, wash with deionized water, and vacuum dry to obtain activated clay;

[0059] S3. Mix 150 g of sodium methoxide and potassium ethoxide by grinding evenly, add hexagonal boron nitride thereto, stir and react at 188 °C for 80 min, cool to room temperature, wash, dry, and add the activated clay to 13000 g of an ethanol aqueous solution with a mass fraction of 55%. Reflux and stir at 115 °C for 80 min, cool to room temperature, centrifuge, and vacuum dry.

[0060] A flame retardant cable material, the raw materials of which include: 1000 g of polyethylene, 25 g of polyolefin thermoplastic elastomer, and 220 g of the above composite flame retardant for cable materials.

[0061] The preparation method of the above flame retardant cable material includes the following steps: Mix polyethylene, polyolefin thermoplastic elastomer, and the above composite flame retardant for cable materials evenly, send them into a two-roll mill, open mill at a temperature of 145 °C for 2 min to melt, plasticize and form at a temperature of 205 °C for 2 min, with a plasticizing pressure of 28 MPa, and carry out electron beam irradiation crosslinking with an irradiation dose of 152 kGy.

[0062] Example 5

[0063] A composite flame retardant for cable materials, the raw materials of which include: 1500 g of palygorskite clay, 150 g of γ-aminopropyltriethoxysilane, 205 g of sodium methoxide, 300 g of ethylenediamine, 800 g of methyl acrylate, 300 g of glyoxylic acid, 150 g of potassium ethoxide, and 1000 g of hexagonal boron nitride with a particle size of 100 - 300 nm.

[0064] The preparation method of the above composite flame retardant for cable materials includes the following steps:

[0065] S1. Add palygorskite clay to 10000 g of deionized water, stir at a speed of 1500 r / min for 15 min, treat with an ultrasonic crusher for 2.5 h, with a treatment power of 900 W, add γ-aminopropyltriethoxysilane, stir at 90 °C for 90 min, cool to room temperature, filter by suction, and vacuum dry to obtain pretreated clay;

[0066] S2. Add the pretreated clay to 4000 g of methanol and stir evenly, add 5 g of potassium methoxide and stir evenly. Under nitrogen protection, add ethylenediamine and methyl acrylate in sequence, stir at 15 °C for 25 h under nitrogen protection, raise the temperature to 35 °C and stir for 10 h, remove nitrogen protection, add a 35% glyoxylic acid solution, stir at 15 °C for 90 min, centrifuge, wash with deionized water, and vacuum dry to obtain activated clay;

[0067] S3. Mix 200 g of sodium methoxide and potassium ethoxide by grinding evenly, add hexagonal boron nitride thereto, stir and react at 185 °C for 90 min, cool to room temperature, wash, dry, and add it to 12000 g of a 60% ethanol aqueous solution together with the activated clay, reflux and stir at 110 °C for 90 min, cool to room temperature, centrifuge, and vacuum dry.

[0068] A flame retardant cable material, the raw materials of which include: 1000 g of polyethylene, 20 g of polyolefin thermoplastic elastomer, and 250 g of the above composite flame retardant for cable materials.

[0069] The preparation method of the above flame retardant cable material includes the following steps: Mix polyethylene, polyolefin thermoplastic elastomer, and the above composite flame retardant for cable materials evenly, feed them into a two-roll mill, knead at 140 °C for 3 min to melt, plasticize and form at 200 °C for 3 min, with a plasticizing pressure of 25 MPa, and carry out electron beam irradiation crosslinking with an irradiation dose of 155 kGy.

[0070] Perform thermogravimetric analysis on the obtained flame retardant cable material in this example at 20 - 600 °C in an oxygen atmosphere with a heating rate of 10 °C / min.

[0071] As Figure 1As shown in the figure, the flame-retardant cable compound obtained in this embodiment starts to decompose at 350 °C, with a concentrated weight loss range, a sharp endothermic peak and a large endothermic amount. The decomposed products are difficult to burn, and combustion is effectively prevented by forming a barrier layer.

[0072] Comparative Example 1

[0073] A composite flame retardant for cable compounds, the raw materials of which include: 1500 g of palygorskite clay, 205 g of sodium methoxide, 300 g of ethylenediamine, 800 g of methyl acrylate, 300 g of glyoxylic acid, 150 g of potassium ethoxide, and 1000 g of hexagonal boron nitride with a particle size of 100 - 300 nm.

[0074] The preparation method of the above-mentioned composite flame retardant for cable compounds includes the following steps:

[0075] S1. Add palygorskite clay to 4000 g of methanol and stir evenly, then add 5 g of potassium methoxide and stir evenly. Under nitrogen protection, add ethylenediamine and methyl acrylate in sequence, stir at 15 °C for 25 h under nitrogen protection, raise the temperature to 35 °C and stir for 10 h, remove nitrogen protection, add a 35% glyoxylic acid solution, stir at 15 °C for 90 min, centrifuge, wash with deionized water, and vacuum dry to obtain activated clay;

[0076] S2. Mix 200 g of sodium methoxide and potassium ethoxide and grind them evenly, add hexagonal boron nitride to it, stir and react at 185 °C for 90 min, cool to room temperature, wash, dry, and add it to 12000 g of 60% ethanol aqueous solution together with the activated clay, reflux and stir at 110 °C for 90 min, cool to room temperature, centrifuge, and vacuum dry.

[0077] A flame-retardant cable compound, the raw materials of which include: 1000 g of polyethylene, 20 g of polyolefin thermoplastic elastomer, and 250 g of the above-mentioned composite flame retardant for cable compounds.

[0078] The preparation method of the above-mentioned flame-retardant cable compound includes the following steps: Mix polyethylene, polyolefin thermoplastic elastomer, and the above-mentioned composite flame retardant for cable compounds evenly, feed them into a two-roll mill, open mill at 140 °C for 3 min to melt, plasticize and form at 200 °C for 3 min, the plasticizing pressure is 25 MPa, and crosslink by electron beam irradiation with an irradiation dose of 155 kGy.

[0079] Comparative Example 2

[0080] A composite flame retardant for cable compounds, the raw materials of which include: 1500 g of palygorskite clay, 150 g of γ-aminopropyltriethoxysilane, 300 g of ethylenediamine, 800 g of methyl acrylate, 300 g of glyoxylic acid, and 1000 g of hexagonal boron nitride with a particle size of 100 - 300 nm.

[0081] The preparation method of the above-mentioned composite flame retardant for cable materials comprises the following steps:

[0082] S1. Add palygorskite clay into 10000 g of deionized water, stir at a speed of 1500 r / min for 15 min, treat with an ultrasonic crusher for 2.5 h, with a treatment power of 900 W, add γ-aminopropyltriethoxysilane, stir at 90 °C for 90 min, cool to room temperature, filter by suction, and dry in vacuum to obtain pretreated clay;

[0083] S2. Add the pretreated clay into 4000 g of methanol and stir evenly, add 5 g of potassium methoxide and stir evenly. Under nitrogen protection, add ethylenediamine and methyl acrylate in sequence, stir at 15 °C for 25 h under nitrogen protection, raise the temperature to 35 °C and stir for 10 h, remove nitrogen protection, add a glyoxylic acid solution with a mass fraction of 35%, stir at 15 °C for 90 min, centrifuge, wash with deionized water, and dry in vacuum to obtain activated clay;

[0084] S3. Add hexagonal boron nitride and activated clay into 12000 g of an ethanol aqueous solution with a mass fraction of 60%, reflux and stir at 110 °C for 90 min, cool to room temperature, centrifuge, and dry in vacuum.

[0085] A flame-retardant cable material, whose raw materials include: 1000 g of polyethylene, 20 g of polyolefin thermoplastic elastomer, and 250 g of the above-mentioned composite flame retardant for cable materials.

[0086] The preparation method of the above-mentioned flame-retardant cable material comprises the following steps: Mix polyethylene, polyolefin thermoplastic elastomer, and the above-mentioned composite flame retardant for cable materials evenly, send them into a two-roll mill, open mill at 140 °C for 3 min to melt, plasticize and form at 200 °C for 3 min, with a plasticizing pressure of 25 MPa, and carry out electron beam irradiation crosslinking with an irradiation dose of 155 kGy.

[0087] Refer to GB / T 1040.2-2022 Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and extrusion plastics to measure the tensile properties (tensile strength, elongation at break) of the flame-retardant cable materials obtained in Example 5 and Comparative Examples 1-2, with a tensile speed of 50 mm / min. Then carry out thermal aging (150 °C × 72 h) on the flame-retardant cable materials obtained in Example 5 and Comparative Examples 1-2, and then measure the tensile properties again, and calculate the tensile property retention rate.

[0088] Tensile property retention rate = Tensile property after thermal aging ÷ Tensile property before thermal aging × 100%

[0089] Such as Figure 2 and Figure 3As shown, the flame-retardant cable compound obtained in Example 5 has the highest tensile strength, and the retention rate of tensile properties is also the highest, superior to Comparative Examples 1-2 (P < 0.05).

[0090] Refer to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Guarded Hot Plate Method" to measure the thermal conductivity of the flame-retardant cable compounds obtained in Example 5 and Comparative Examples 1-2.

[0091] Refer to GB / T 2406.2-2009 "Plastics - Determination of Flammability by the Oxygen Index Method - Part 2: Room Temperature Tests" to measure the oxygen index (LOI) of the flame-retardant cable compounds obtained in Example 5 and Comparative Examples 1-2.

[0092] As Figure 4 shown, the flame-retardant cable compound obtained in Example 5 has the highest thermal conductivity and oxygen index, superior to Comparative Examples 1-2 (P < 0.05).

[0093] Refer to the vertical burning test in GB / T 2408-2021 "Plastics - Determination of Burning Behavior - Horizontal and Vertical Methods" to conduct a classification assessment on the flame-retardant cable compounds obtained in Example 5 and Comparative Examples 1-2. The flame-retardant cable compound obtained in Example 5 is V-0, while those obtained in Comparative Examples 1-2 are both V-1.

[0094] The applicant believes that the reason for the above results is as follows: After the palygorskite clay is pretreated in the present invention, hyperbranched polyamidoamine is combined on its surface, which can not only greatly enhance the dispersibility of palygorskite clay in the polyethylene matrix, and then carboxylate the end groups through glyoxylic acid treatment. Combining with the unique cavity structure and three-dimensional structure of hyperbranched polyamidoamine, it is more conducive to the uniformity of palygorskite clay in all directions in the polyethylene matrix. Moreover, palygorskite clay can form a skeleton in the polyethylene matrix and promote the formation of a new network, significantly improving the mechanical properties and flame retardancy of the polyethylene matrix and enhancing the durability of the cable compound. In the present invention, hexagonal boron nitride is treated by hydroxylation, which can effectively increase the reactivity between hexagonal boron nitride and activated clay. The activated clay obtained in the present invention contains a large number of carboxyl groups on its surface, which can combine with the hydroxyl groups on the surface of boron nitride. Not only is the binding strength high, but due to the special flaky hexagonal structure of boron nitride, it can be evenly combined onto the palygorskite clay structure. The two act synergistically to have excellent thermal conductivity while improving the flame retardancy.

[0095] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A composite flame retardant for cable materials, characterized in that: The raw materials include, by mass: 10-20 parts of palygorskite clay, 1-2 parts of γ-aminopropyltriethoxysilane, 1.01-3.1 parts of sodium methoxide, 1-5 parts of ethylenediamine, 5-10 parts of methyl acrylate, 1.5-6 parts of glyoxylic acid, 1-2 parts of potassium ethoxide, and 5-15 parts of hexagonal boron nitride; Prepared by the following steps: S1. Add palygorskite clay to deionized water and stir for 10-20 min, perform ultrasonic grinding for 1-4 h, add γ-aminopropyltriethoxysilane, stir at 85-95° C. for 1-2 h, cool to room temperature, filter, and vacuum dry to obtain pretreated clay; S2, adding the pretreated clay to methanol and stirring evenly, adding sodium methoxide and stirring evenly, adding ethylenediamine and methyl acrylate in sequence under nitrogen protection, stirring at 10-20° C. for 20-30 hours under nitrogen protection, heating to 30-40° C. and stirring for 5-15 hours, removing nitrogen protection, adding glyoxylic acid solution, stirring at 10-20° C. for 1-2 hours, centrifuging, washing, and vacuum drying to obtain activated clay; S3. Mix and grind sodium methoxide and potassium ethoxide evenly, add hexagonal boron nitride, react at 180-190°C with stirring for 1-2h, cool to room temperature, wash, dry, add to ethanol aqueous solution with activated clay, reflux and stir at 100-120°C for 1-2h, cool to room temperature, centrifuge, and dry in vacuo.

2. The composite flame retardant for cable materials according to claim 1, characterized in that: The particle size of hexagonal boron nitride is 100-300nm.

3. A method for preparing a composite flame retardant for cable materials as claimed in claim 1 or 2, characterized in that: The steps include: S1. Add palygorskite clay to deionized water and stir for 10-20 min, perform ultrasonic grinding for 1-4 h, add γ-aminopropyltriethoxysilane, stir at 85-95° C. for 1-2 h, cool to room temperature, filter, and vacuum dry to obtain pretreated clay; S2, adding the pretreated clay to methanol and stirring evenly, adding sodium methoxide and stirring evenly, adding ethylenediamine and methyl acrylate in sequence under nitrogen protection, stirring at 10-20° C. for 20-30 hours under nitrogen protection, heating to 30-40° C. and stirring for 5-15 hours, removing nitrogen protection, adding glyoxylic acid solution, stirring at 10-20° C. for 1-2 hours, centrifuging, washing, and vacuum drying to obtain activated clay; S3. Mix and grind sodium methoxide and potassium ethoxide evenly, add hexagonal boron nitride, react at 180-190°C with stirring for 1-2h, cool to room temperature, wash, dry, add to ethanol aqueous solution with activated clay, reflux and stir at 100-120°C for 1-2h, cool to room temperature, centrifuge, and dry in vacuo.

4. The method for preparing the composite flame retardant for cable materials according to claim 3, characterized in that: In S1, the ultrasonic pulverization treatment power is 800-1000W.

5. The method for preparing the composite flame retardant for cable materials according to claim 3, characterized in that: In S2, the mass fraction of the glyoxylic acid solution is 30-40%.

6. The method for preparing the composite flame retardant for cable materials according to claim 3, characterized in that: The mass ratio of the sodium methoxide used in S2 to the sodium methoxide used in S3 is 0.01-0.1:1-3.

7. The method for preparing the composite flame retardant for cable materials according to claim 3, characterized in that: In S3, the mass fraction of the ethanol aqueous solution is 50-70%.

8. A flame retardant cable material, characterized in that: The raw materials include: the composite flame retardant for cable materials as claimed in claim 1 or 2, and polyethylene.

9. The flame-retardant cable material according to claim 8, characterized in that: The raw materials include, by mass, 100 parts of polyethylene, 1-3 parts of a toughening agent, and 20-30 parts of the composite flame retardant for cable materials as claimed in claim 1 or 2.

10. A method for preparing the flame-retardant cable material according to claim 8 or 9, characterized in that: The method comprises the following steps: uniformly mixing polyethylene, a toughening agent and the composite flame retardant for cable materials as claimed in claim 1 or 2, refining at 130-150° C. for 1-5 minutes, melting, plasticizing and molding at 190-210° C. for 1-5 minutes, with a plasticizing pressure of 20-30 MPa, and crosslinking by electron beam irradiation with an irradiation dose of 150-160 kGy.

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