Low-smoke halogen-free flame-retardant polyolefin cable material and preparation process thereof

Abstract

The invention relates to the technical field of cable materials, in particular to a low-smoke halogen-free flame-retardant polyolefin cable material and a preparation process thereof. The low-smoke halogen-free flame-retardant polyolefin cable material is obtained by uniformly mixing the ethylene-vinyl acetate copolymer, the polyethylene, the compatilizer, the halogen-free flame retardant, the fuming inhibitor, the carbon black, the lubricant and the antioxidant and carrying out extrusion granulation. The low-smoke halogen-free flame-retardant polyolefin cable material comprises the following components in parts by weight: 60-80 parts of an ethylene-vinyl acetate copolymer, 20-40 parts of polyethylene, 10-20 parts of a compatilizer, 50-60 parts of a halogen-free flame retardant, 15-30 parts of a fuming inhibitor, 5-10 parts of carbon black, 1-3 parts of a lubricant and 1-2 parts of an antioxidant. The low-smoke halogen-free flame-retardant polyolefin cable material prepared by the invention has excellent mechanical properties, flame retardance and aging resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of cable materials, and specifically to a low-smoke and halogen-free flame-retardant polyolefin cable material and its preparation process. Background Art

[0002] With the increasingly strict global environmental protection regulations and the improvement of fire safety requirements, the application demand for low-smoke and halogen-free flame-retardant polyolefin cable materials has increased significantly in the fields of electricity, communication, construction, etc. Polyolefins (such as polyethylene, polypropylene, etc.) have excellent electrical properties, chemical stability and processing properties. They have relatively low costs and wide sources, and are important matrix materials for cable materials. However, the flame retardancy of pure polyolefin materials is poor and needs to be modified to meet the flame retardant requirements of cables. By adding flame retardants to polyolefins, the characteristics of low smoke and halogen-free flame retardancy can be imparted while maintaining their original excellent properties.

[0003] Traditional halogen-containing flame-retardant cable materials (such as chlorine- and bromine-containing compounds) have excellent flame retardant properties, but they will release a large amount of toxic hydrogen halide gases and thick smoke when burning, which not only seriously pollutes the environment, but also poses a great threat to the safety of personnel evacuation and rescue. Therefore, the halogen-free flame-retardant system has gradually become a research hotspot. However, the existing technologies still face the following key problems: First, inorganic flame retardants (such as aluminum hydroxide, magnesium hydroxide) need to be filled in a large amount to achieve a good flame retardant effect, but this often leads to significant deterioration of the mechanical properties of the material, and the processing fluidity becomes poor, and surface roughness or fracture defects are likely to occur; Second, although organic halogen-free flame retardants (such as DOPO derivatives, intumescent flame retardants) can reduce the filling amount, they have poor compatibility with the polyolefin matrix and are prone to migration and precipitation during long-term use, resulting in attenuation of flame retardant performance and accelerated material aging; In addition, the existing formulations have shortcomings in suppressing smoke and toxic gases, and many technologies focus on the optimization of single performance, and it is difficult to balance flame retardant efficiency, low smoke and low toxicity, mechanical strength and thermal stability.

[0004] Therefore, we propose a low-smoke and halogen-free flame-retardant polyolefin cable material and its preparation process. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-smoke and halogen-free flame-retardant polyolefin cable material and its preparation process to solve the problems raised in the existing technologies.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A low-smoke and halogen-free flame-retardant polyolefin cable material, comprising the following weight components: 60-80 parts of ethylene-vinyl acetate copolymer, 20-40 parts of polyethylene, 10-20 parts of compatibilizer, 50-60 parts of halogen-free flame retardant, 15-30 parts of smoke suppressant, 5-10 parts of carbon black, 1-3 parts of lubricant, and 1-2 parts of antioxidant.

[0008] Further, the compatibilizer is one or a mixture of more than one of maleic anhydride grafted polyethylene, maleic anhydride grafted ethylene vinyl acetate, maleic anhydride grafted ethylene octene copolymer, maleic anhydride grafted ethylene propylene rubber, and ethylene acrylate maleic anhydride terpolymer.

[0009] Further, the preparation method of the halogen-free flame retardant is as follows:

[0010] Step A: Under nitrogen protection, mix 4-hydroxyphenylboronic acid and tetrahydrofuran evenly. Under ice bath conditions, add methylvinyldichlorosilane and triethylamine, and react for 2 - 4 h. Continue to react at room temperature for 8 - 10 h. After precipitation, filtration, washing, and drying, vinyl borosilicon compound is obtained;

[0011] Step B: Mix DOPO, 3,4-dihydroxystyrene acid, a catalyst, and N,N-dimethylformamide, and react at a temperature of 110 - 130 °C for 12 - 24 h. After extraction with acetone, rotary evaporation, and drying, modified DOPO is obtained;

[0012] Step C: Mix the modified DOPO, vinyl borosilicon compound, and N,N-dimethylformamide evenly, react for 4 - 6 h to obtain an intermediate, then add 2-mercaptobenzimidazole and a photoinitiator, and after ultraviolet light irradiation, a halogen-free flame retardant is obtained.

[0013] Further, in the said Step A, the molar ratio of 4-hydroxyphenylboronic acid to methylvinyldichlorosilane is (2.1 - 2.2) : 1.

[0014] Further, the mass of the tetrahydrofuran is 2 - 4 times the total mass of 4-hydroxyphenylboronic acid and methylvinyldichlorosilane.

[0015] Further, the dosage of the triethylamine is 0.3 - 0.5 times the total mass of 4-hydroxyphenylboronic acid and methylvinyldichlorosilane.

[0016] Further, in the said Step B, the molar ratio of DOPO to 3,4-dihydroxystyrene acid is 1 : (1 - 1.2).

[0017] Further, the dosage of the catalyst is 0.8 - 1.2% of the total mass of DOPO and 3,4-dihydroxystyrene acid.

[0018] Further, the mass of the N,N-dimethylformamide is 2 - 4 times the total mass of DOPO and 3,4-dihydroxystyrene acid.

[0019] Further, the catalyst is at least one of sodium hexachloroplatinate(VI) hexahydrate (CAS: 16923 - 58 - 3), platinum dioxide, and ruthenium trichloride.

[0020] Further, in the step C, the molar ratio of the modified DOPO to the vinyl borosilicate compound is 1:(1.0 - 1.5).

[0021] Further, the mass of the N,N-dimethylformamide is 3 - 5 times the total mass of the modified DOPO and the vinyl borosilicate compound.

[0022] Further, the molar ratio of the intermediate to 2-mercaptobenzimidazole is 1:(1.0 - 1.2).

[0023] Further, the photoinitiator is one or more of 2-hydroxy-methylphenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholin-1-one, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0024] Further, the process conditions for the ultraviolet light irradiation are: irradiation time of 0.5 - 2.0 h under ultraviolet light of 360 - 400 nm, and irradiation intensity of 20 - 35 mW / cm 2 。

[0025] Further, the fume inhibitor is compounded from 10 - 20 parts of aluminum hydroxide and 5 - 10 parts of magnesium hydroxide.

[0026] Further, the lubricant is one or more mixtures of zinc stearate, calcium stearate, and polyethylene wax.

[0027] Further, the antioxidant is antioxidant 1010.

[0028] A preparation process of a low-smoke and halogen-free flame-retardant polyolefin cable material comprises the following steps:

[0029] Mix ethylene-vinyl acetate copolymer, polyethylene, compatibilizer, halogen-free flame retardant, fume inhibitor, carbon black, lubricant, and antioxidant evenly, and extrude and pelletize to obtain the low-smoke and halogen-free flame-retardant polyolefin cable material.

[0030] Further, in the extrusion and pelletizing process, a twin-screw extruder is used, the extrusion temperature is 150 - 170°C, and the rotation speed is 300 - 500 r / min.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. A low-smoke and halogen-free flame-retardant polyolefin cable compound and its preparation process according to the present invention. First, the hydroxyl group in 4-hydroxybenzeneboronic acid reacts with methylvinyldichlorosilane to form a boron- and silicon-containing vinyl compound, namely vinyl borosilicon compound. Then, DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) reacts with the double bond in 3,4-dihydroxystyrenic acid to introduce active hydroxyl groups, obtaining modified DOPO. The remaining boric acid groups of the vinyl borosilicon compound react with the modified DOPO to obtain an intermediate. Finally, an antioxidant (2-mercaptobenzimidazole) is introduced into the flame retardant molecular chain through a thiol-ene click reaction to achieve chemical bonding of the antioxidant, solving the problems of antioxidant migration and precipitation caused by traditional physical blending. Eventually, a halogen-free flame retardant with both flame retardant and antioxidant functions is prepared, containing phosphorus (P), silicon (Si), boron (B), and sulfur (S) elements. Among them, the P element captures free radicals through a gas-phase flame retardant mechanism to inhibit the combustion chain reaction; the Si and B elements form a dense ceramicized carbon layer in the condensed phase to isolate heat and oxygen; the S element promotes crosslinking of the carbon layer to enhance its stability and barrier properties. The synergistic effect of multiple elements significantly improves the flame retardant efficiency. At the same time, the antioxidant can synergistically interact with the antioxidant (hindered phenolic antioxidant) in the components to jointly improve the aging resistance of the cable compound.

[0033] 2. A low-smoke and halogen-free flame-retardant polyolefin cable compound and its preparation process according to the present invention uses aluminum hydroxide (ATH) and magnesium hydroxide (MH) in a compounded form as a smoke suppressant. Both decompose endothermically at high temperatures to synergistically reduce the combustion temperature and inhibit smoke generation. To further improve the flame retardant effect, the halogen-free flame retardant of the present invention is combined with the ATH / MH compounded system in the solution to form a multiple barrier mechanism, and together with the joint action of ethylene-vinyl acetate copolymer, polyethylene, compatibilizer, carbon black, lubricant, and antioxidant, a low-smoke and halogen-free flame-retardant polyolefin cable compound is prepared. In case of a fire, it can slow down the combustion speed and inhibit the spread of flames, and also has the characteristics of less smoke volume, less release of harmful gases, and low flue gas toxicity, which can reduce the impact on the environment. Specific embodiments

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] In this embodiment, ethylene-vinyl acetate copolymer: grade is Hanwha Chemical 1828; polyethylene: high-density polyethylene, grade is Lotte Chemical 2600F; compatibilizer: maleic anhydride grafted polyethylene, grade is DuPont E528 of the United States; carbon black: grade is Cabot N330; lubricant: Honeywell polyethylene wax AC-6; aluminum hydroxide: Zhonglv brand H-WF-8; magnesium hydroxide: Aitemag 10FG of Aitek; the antioxidant is antioxidant 1010.

[0036] Unless otherwise specified, the following parts are all parts by mass.

[0037] Example 1: A preparation process of a low-smoke and halogen-free flame-retardant polyolefin cable material, including the following processes:

[0038] Mix 60 parts of ethylene-vinyl acetate copolymer, 20 parts of polyethylene, 10 parts of compatibilizer, 50 parts of halogen-free flame retardant, 15 parts of smoke suppressant (compounded by 10 parts of aluminum hydroxide and 5 parts of magnesium hydroxide), 1 part of lubricant and 1 part of antioxidant evenly, and extrude and pelletize (using a twin-screw extruder, the extrusion temperature is 150 - 170 °C, and the rotation speed is 300 - 500 r / min) to obtain a low-smoke and halogen-free flame-retardant polyolefin cable material;

[0039] The preparation method of the halogen-free flame retardant is as follows:

[0040] Step A: Under nitrogen protection, mix 4-hydroxyphenylboronic acid and tetrahydrofuran evenly. Under ice bath conditions, add methylvinyldichlorosilane and triethylamine, react for 2 h, and continue to react at room temperature for 8 h. After precipitation, filtration, washing, and drying, obtain vinyl borosilicon compound; the molar ratio of 4-hydroxyphenylboronic acid to methylvinyldichlorosilane is 2.1:1; the mass of tetrahydrofuran is 2 times the total mass of 4-hydroxyphenylboronic acid and methylvinyldichlorosilane; the dosage of triethylamine is 0.3 times the total mass of 4-hydroxyphenylboronic acid and methylvinyldichlorosilane;

[0041] Step B: Mix DOPO, 3,4-dihydroxystyrenic acid, sodium hexachloroplatinate(VI) hexahydrate and N,N-dimethylformamide, and react at 110 °C for 24 h. After acetone extraction, rotary evaporation, and drying, obtain modified DOPO; the molar ratio of DOPO to 3,4-dihydroxystyrenic acid is 1:1; the dosage of sodium hexachloroplatinate(VI) hexahydrate is 0.8% of the total mass of DOPO and 3,4-dihydroxystyrenic acid; the mass of N,N-dimethylformamide is 2 times the total mass of DOPO and 3,4-dihydroxystyrenic acid;

[0042] Step C: Mix the modified DOPO, vinyl borosilicate compound, and N,N-dimethylformamide evenly, react for 4 h to obtain an intermediate, then add 2-mercaptobenzimidazole and 2-hydroxy-2-methylpropiophenone, and irradiate under ultraviolet light at 360 nm for 0.5 h with an irradiation intensity of 35 mW / cm 2 , to obtain a halogen-free flame retardant; the molar ratio of the modified DOPO to the vinyl borosilicate compound is 1:1; the mass of N,N-dimethylformamide is 3 times the total mass of the modified DOPO and the vinyl borosilicate compound; the molar ratio of the intermediate to 2-mercaptobenzimidazole is 1:1.

[0043] Example 2: A preparation process of a low-smoke halogen-free flame-retardant polyolefin cable material, including the following processes:

[0044] Mix 70 parts of ethylene-vinyl acetate copolymer, 30 parts of polyethylene, 15 parts of compatibilizer, 55 parts of halogen-free flame retardant, 22 parts of smoke suppressant (compounded by 15 parts of aluminum hydroxide and 7 parts of magnesium hydroxide), 2 parts of lubricant, and 1.5 parts of antioxidant evenly, and extrude and pelletize (using a twin-screw extruder, with an extrusion temperature of 160 °C and a rotation speed of 400 r / min) to obtain a low-smoke halogen-free flame-retardant polyolefin cable material;

[0045] The preparation method of the halogen-free flame retardant is as follows:

[0046] Step A: Under nitrogen protection, mix 4-hydroxybenzeneboronic acid and tetrahydrofuran evenly, add methylvinyldichlorosilane and triethylamine under ice bath conditions, react for 3 h, and continue to react at room temperature for 9 h. After precipitation, filtration, washing, and drying, obtain a vinyl borosilicate compound; the molar ratio of 4-hydroxybenzeneboronic acid to methylvinyldichlorosilane is 2.15:1; the mass of tetrahydrofuran is 3 times the total mass of 4-hydroxybenzeneboronic acid and methylvinyldichlorosilane; the dosage of triethylamine is 0.4 times the total mass of 4-hydroxybenzeneboronic acid and methylvinyldichlorosilane;

[0047] Step B: Mix DOPO, 3,4-dihydroxystyrene acid, sodium hexachloroplatinate(VI) hexahydrate, and N,N-dimethylformamide, and react at 120 °C for 18 h. After acetone extraction, rotary evaporation, and drying, obtain modified DOPO; the molar ratio of DOPO to 3,4-dihydroxystyrene acid is 1:1.1; the dosage of sodium hexachloroplatinate(VI) hexahydrate is 1% of the total mass of DOPO and 3,4-dihydroxystyrene acid; the mass of N,N-dimethylformamide is 3 times the total mass of DOPO and 3,4-dihydroxystyrene acid;

[0048] Step C: Mix the modified DOPO, vinyl borosilicate compound, and N,N-dimethylformamide uniformly, react for 5 h to obtain an intermediate, then add 2-mercaptobenzimidazole and 2-hydroxy-methylphenylpropan-1-one, and irradiate under ultraviolet light at 380 nm for 1 h with an irradiation intensity of 25 mW / cm 2 , to obtain a halogen-free flame retardant; the molar ratio of modified DOPO to vinyl borosilicate compound is 1:1.3; the mass of N,N-dimethylformamide is 4 times the total mass of modified DOPO and vinyl borosilicate compound; the molar ratio of the intermediate to 2-mercaptobenzimidazole is 1:1.1.

[0049] Example 3: A preparation process of a low-smoke halogen-free flame-retardant polyolefin cable material, including the following processes:

[0050] Mix 80 parts of ethylene-vinyl acetate copolymer, 40 parts of polyethylene, 20 parts of compatibilizer, 60 parts of halogen-free flame retardant, 30 parts of smoke suppressant (composed of 20 parts of aluminum hydroxide and 10 parts of magnesium hydroxide), 3 parts of lubricant, and 2 parts of antioxidant, and extrude and pelletize (using a twin-screw extruder, with an extrusion temperature of 170 °C and a rotation speed of 500 r / min) to obtain a low-smoke halogen-free flame-retardant polyolefin cable material.

[0051] The preparation method of the halogen-free flame retardant is as follows:

[0052] Step A: Under nitrogen protection, mix 4-hydroxybenzeneboronic acid and tetrahydrofuran uniformly, add methylvinyldichlorosilane and triethylamine under ice bath conditions, react for 4 h, and continue to react at room temperature for 10 h. After precipitation, filtration, washing, and drying, obtain vinyl borosilicate compound; the molar ratio of 4-hydroxybenzeneboronic acid to methylvinyldichlorosilane is 2.2:1; the mass of tetrahydrofuran is 4 times the total mass of 4-hydroxybenzeneboronic acid and methylvinyldichlorosilane; the dosage of triethylamine is 0.5 times the total mass of 4-hydroxybenzeneboronic acid and methylvinyldichlorosilane;

[0053] Step B: Mix DOPO, 3,4-dihydroxystyrene acid, sodium hexachloroplatinate(VI) hexahydrate, and N,N-dimethylformamide, and react at 130 °C for 12 h. After acetone extraction, rotary evaporation, and drying, obtain modified DOPO; the molar ratio of DOPO to 3,4-dihydroxystyrene acid is 1:1.2; the dosage of the catalyst is 1.2% of the total mass of DOPO and 3,4-dihydroxystyrene acid; the mass of N,N-dimethylformamide is 4 times the total mass of DOPO and 3,4-dihydroxystyrene acid;

[0054] Step C: Mix the modified DOPO, vinyl borosilicate compound, and N,N-dimethylformamide evenly, react for 6 h to obtain an intermediate, then add 2-mercaptobenzimidazole and 2-hydroxy-methylphenylpropan-1-one, and irradiate under ultraviolet light at 400 nm for 2 h with an irradiation intensity of 20 mW / cm 2 , to obtain a halogen-free flame retardant; the molar ratio of the modified DOPO to the vinyl borosilicate compound is 1:1.5; the mass of N,N-dimethylformamide is 5 times the total mass of the modified DOPO and the vinyl borosilicate compound; the molar ratio of the intermediate to 2-mercaptobenzimidazole is 1:1.2.

[0055] Comparative Example 1: A preparation process of a low-smoke halogen-free flame-retardant polyolefin cable material, including the following process:

[0056] Mix 70 parts of ethylene-vinyl acetate copolymer, 30 parts of polyethylene, 15 parts of compatibilizer, 55 parts of DOPO, 22 parts of smoke suppressant (compounded from 15 parts of aluminum hydroxide and 7 parts of magnesium hydroxide), 2 parts of lubricant, and 1.5 parts of antioxidant evenly, and extrude and pelletize (using a twin-screw extruder, the extrusion temperature is 160 °C and the rotation speed is 400 r / min) to obtain a low-smoke halogen-free flame-retardant polyolefin cable material;

[0057] Compared with Example 2, in Comparative Example 1, the halogen-free flame retardant is replaced with the same mass of DOPO.

[0058] Comparative Example 2: A preparation process of a low-smoke halogen-free flame-retardant polyolefin cable material, including the following process:

[0059] The preparation method of the halogen-free flame retardant is as follows:

[0060] Step A: Under nitrogen protection, mix 4-hydroxybenzeneboronic acid and tetrahydrofuran evenly, add methylvinyldichlorosilane and triethylamine under ice bath conditions, react for 3 h, and continue to react at room temperature for 9 h. After precipitation, filtration, washing, and drying, obtain a vinyl borosilicate compound; the molar ratio of 4-hydroxybenzeneboronic acid to methylvinyldichlorosilane is 2.15:1; the mass of tetrahydrofuran is 3 times the total mass of 4-hydroxybenzeneboronic acid and methylvinyldichlorosilane; the dosage of triethylamine is 0.4 times the total mass of 4-hydroxybenzeneboronic acid and methylvinyldichlorosilane;

[0061] Step B: Mix DOPO, 3,4-dihydroxycinnamic acid, sodium hexachloroplatinate(VI) hexahydrate, and N,N-dimethylformamide, and react at 120 °C for 18 h. After extraction with acetone, rotary evaporation, and drying, modified DOPO is obtained; the molar ratio of DOPO to 3,4-dihydroxycinnamic acid is 1:1.1; the amount of sodium hexachloroplatinate(VI) hexahydrate is 1% of the total mass of DOPO and 3,4-dihydroxycinnamic acid; the mass of N,N-dimethylformamide is 3 times the total mass of DOPO and 3,4-dihydroxycinnamic acid.

[0062] Step C: Mix modified DOPO, vinyl borosilicon compound, and N,N-dimethylformamide evenly and react for 5 h to obtain a halogen-free flame retardant; the molar ratio of modified DOPO to vinyl borosilicon compound is 1:1.3; the mass of N,N-dimethylformamide is 4 times the total mass of modified DOPO and vinyl borosilicon compound.

[0063] Compared with Example 2, in Comparative Example 2, 2-mercaptobenzimidazole and photoinitiator are not added, and other steps are the same as those in Example 2.

[0064] Comparative Example 3: A preparation process of a low-smoke halogen-free flame-retardant polyolefin cable material includes the following processes:

[0065] The preparation method of the halogen-free flame retardant is as follows:

[0066] Step A: Under nitrogen protection, mix 4-hydroxyphenylboronic acid and tetrahydrofuran evenly. Under ice bath conditions, add methylvinyldichlorosilane and triethylamine and react for 3 h. Continue to react at room temperature for 9 h. After precipitation, filtration, washing, and drying, vinyl borosilicon compound is obtained; the molar ratio of 4-hydroxyphenylboronic acid to methylvinyldichlorosilane is 2.15:1; the mass of tetrahydrofuran is 3 times the total mass of 4-hydroxyphenylboronic acid and methylvinyldichlorosilane; the amount of triethylamine is 0.4 times the total mass of 4-hydroxyphenylboronic acid and methylvinyldichlorosilane.

[0067] Step B: Mix DOPO, 3,4-dihydroxycinnamic acid, sodium hexachloroplatinate(VI) hexahydrate, and N,N-dimethylformamide, and react at 120 °C for 18 h. After extraction with acetone, rotary evaporation, and drying, modified DOPO is obtained; the molar ratio of DOPO to 3,4-dihydroxycinnamic acid is 1:1.1; the amount of sodium hexachloroplatinate(VI) hexahydrate is 1% of the total mass of DOPO and 3,4-dihydroxycinnamic acid; the mass of N,N-dimethylformamide is 3 times the total mass of DOPO and 3,4-dihydroxycinnamic acid.

[0068] Step C: Mix the modified DOPO, vinyl borosilicate compound and N,N-dimethylformamide evenly, react for 5 h to obtain an intermediate, then add 2-mercaptobenzimidazole and 2-hydroxy-methylphenylpropane-1-one, and irradiate under ultraviolet light at 380 nm for 1 h with an irradiation intensity of 25 mW / cm 2 , to obtain a halogen-free flame retardant; the mass of N,N-dimethylformamide is 4 times the total mass of the modified DOPO and vinyl borosilicate compound; the molar ratio of the intermediate to 2-mercaptobenzimidazole is 1:1.1;

[0069] Compared with Example 2, in Step C of Comparative Example 3, the molar ratio of the modified DOPO to the vinyl borosilicate compound is 1:0.5, and the other steps are the same as those in Example 2.

[0070] Experiment: Take the low-smoke halogen-free flame-retardant polyolefin cable materials obtained in Examples 1-3 and Comparative Examples 1-3, inject them into test specimens, and detect their properties respectively and record the test results:

[0071] The tensile properties are tested according to GB / T 1040.3-2006 "Plastics - Determination of tensile properties", using a universal electronic tensile testing machine, at room temperature, with a tensile rate of 50 mm / min, and the test specimen size is 100 mm×10 mm×1 mm; hang the test specimen in a heat aging oven, conduct an accelerated heat aging test at 180 °C for 7 d, and then conduct the tensile property test again; the limiting oxygen index is tested according to GB / T 2406.2-2009 "Plastics - Determination of burning behavior by the oxygen index method - Part 2: Ambient temperature test", and the test specimen size is 100 mm×6.5 mm×3 mm.

[0072] The test results are shown in Table 1.

[0073] Table 1: Test data of the low-smoke halogen-free flame-retardant polyolefin cable materials prepared in Examples 1-3 and Comparative Examples 1-3

[0074]

[0075] From the data in the above table, the following conclusions can be clearly obtained:

[0076] As can be seen from Table 1, compared with Comparative Examples 1-3, the low-smoke and halogen-free polyolefin cable compounds prepared in Examples 1-3 not only have the characteristics of flame retardancy and low smoke, but also have excellent mechanical properties and aging resistance. In Comparative Example 1, when the halogen-free flame retardant was replaced with DOPO, the oxygen index, tensile properties and aging resistance of the material all decreased. In Comparative Example 2, 2-mercaptobenzimidazole was not introduced, and the change rates of tensile strength and elongation at break after the thermal aging test of the obtained product were both large. It can be seen that the introduction of 2-mercaptobenzimidazole can improve the heat aging resistance of the material. In Comparative Example 4, the addition amount of the vinyl borosilicon compound was reduced, and the oxygen index decreased, resulting in a decrease in the flame retardant effect.

[0077] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A low-smoke and halogen-free flame-retardant polyolefin cable compound, characterized in that: It comprises the following weight components: 60 - 80 parts of ethylene-vinyl acetate copolymer, 20 - 40 parts of polyethylene, 10 - 20 parts of compatibilizer, 50 - 60 parts of halogen-free flame retardant, 15 - 30 parts of smoke suppressant, 5 - 10 parts of carbon black, 1 - 3 parts of lubricant, and 1 - 2 parts of antioxidant.

2. The low-smoke and halogen-free flame-retardant polyolefin cable compound according to claim 1, characterized in that: The preparation method of the halogen-free flame retardant is as follows: Step A: Under nitrogen protection, 4-hydroxyphenylboronic acid and tetrahydrofuran are mixed evenly. Under ice bath conditions, methylvinyldichlorosilane and triethylamine are added, and the reaction is carried out for 2 - 4 h. The reaction continues at room temperature for 8 - 10 h. After precipitation, filtration, washing, and drying, a vinyl borosilicon compound is obtained; Step B: DOPO, 3,4-dihydroxystyrene acid, a catalyst, and N,N-dimethylformamide are mixed and reacted at a temperature of 110 - 130 °C for 12 - 24 h. After acetone extraction, rotary evaporation, and drying, modified DOPO is obtained; Step C: Modified DOPO, vinyl borosilicon compound, and N,N-dimethylformamide are mixed evenly and reacted for 4 - 6 h to obtain an intermediate. Then, 2-mercaptobenzimidazole and a photoinitiator are added. After ultraviolet light irradiation, a halogen-free flame retardant is obtained.

3. The low-smoke and halogen-free flame-retardant polyolefin cable compound according to claim 2, wherein: In step A, the molar ratio of 4-hydroxyphenylboronic acid to methylvinyldichlorosilane is (2.1 - 2.2):

1.

4. The low-smoke and halogen-free flame-retardant polyolefin cable compound according to claim 2, characterized in that: In step B, the molar ratio of DOPO to 3,4-dihydroxystyrene acid is 1:(1.0 - 1.2).

5. The low-smoke and halogen-free flame-retardant polyolefin cable compound according to claim 2, characterized in that: In step C, the molar ratio of modified DOPO to vinyl borosilicon compound is 1:(1.0 - 1.5).

6. The low-smoke and halogen-free flame-retardant polyolefin cable compound according to claim 1, wherein: The compatibilizer is one or a mixture of maleic anhydride grafted polyethylene, maleic anhydride grafted ethylene-vinyl acetate, maleic anhydride grafted ethylene-octene copolymer, maleic anhydride grafted ethylene-propylene rubber, and ethylene acrylate maleic anhydride terpolymer.

7. The low-smoke and halogen-free flame-retardant polyolefin cable compound according to claim 1, wherein: The smoke suppressant is composed of 10 - 20 parts of aluminum hydroxide and 5 - 10 parts of magnesium hydroxide compounded.

8. The low-smoke and halogen-free flame-retardant polyolefin cable compound according to claim 1, wherein: The lubricant is one or a mixture of zinc stearate, calcium stearate, and polyethylene wax.

9. The preparation process of a low-smoke and halogen-free flame-retardant polyolefin cable compound according to any one of claims 1-8, characterized in that: It includes the following steps: The ethylene-vinyl acetate copolymer, polyethylene, compatibilizer, halogen-free flame retardant, smoke suppressant, carbon black, lubricant, and antioxidant are mixed evenly and extruded into pellets to obtain a low-smoke halogen-free flame-retardant polyolefin cable material.

10. The preparation process of a low-smoke and halogen-free flame-retardant polyolefin cable material according to claim 9, characterized in that: In the extrusion granulation process, a twin-screw extruder is used, the extrusion temperature is 150 - 170 °C, and the rotation speed is 300 - 500 r / min.

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