A general-purpose low-smoke halogen-free steel cord core fire-retardant conveyor belt and a preparation method thereof

Abstract

The present application belongs to the technical field of conveying belt, and particularly relates to a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveying belt and a preparation method thereof. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveying belt comprises a steel wire rope core, a core rubber layer wrapped outside the steel wire rope core, and a covering rubber layer covering the core rubber layer. The core rubber layer comprises the following components: ethylene-propylene-diene rubber, natural rubber, tackifying resin, cobalt salt, vulcanization activator, magnesium oxide, reinforcing agent, poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), vulcanization accelerator, antioxidant, vulcanizing agent, antimony trioxide, four-component flame-retardant synergist, carbon-forming flame retardant, and softener. The core rubber layer of the flame-retardant conveying belt has good adhesive strength and excellent mechanical properties, and can meet the requirements of various physical and chemical indexes. In addition, the conveying belt also has good low-smoke halogen-free and flame-retardant properties, and meets the urgent needs of modern industry for safe and efficient, long-life conveying equipment.

Description

Technical Field

[0001] This invention belongs to the field of conveyor belt technology, and particularly relates to a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt and its preparation method. Background Technology

[0002] Steel cord conveyor belts are high-performance conveyor belts designed specifically for long-distance, high-capacity, and high-speed material transport, possessing exceptional strength and durability. Compared to traditional fabric-core conveyor belts, steel cord conveyor belts are more robust and reliable, with extremely high toughness and strength, significantly improving the reliability of conveying systems, reducing maintenance and replacement frequency, and lowering maintenance costs, making them the preferred choice for modern industrial conveying systems. Flame-retardant steel cord conveyor belts consist of a cover rubber layer, a steel cord core, and a core rubber layer, manufactured through shaping and vulcanization. The strong adhesion between the core rubber layer and the steel cord prevents corrosion of the steel cord, thereby extending the service life of the steel cord conveyor belt.

[0003] The underground environment in coal mines is extremely unique and harsh, characterized by enclosed spaces, poor ventilation, and the accumulation of methane and coal dust, posing a very high fire risk. Therefore, in underground coal mine operations, conveyor belts must not only meet stringent safety standards such as flame retardancy, low smoke, and halogen-free properties, but also have improved mechanical properties and service life. One of the core technical indicators affecting the service life of steel cord conveyor belts is the bonding strength between the steel cord and the core rubber layer. Currently, cobalt salts are mainly introduced into the core rubber layer as adhesion promoters. However, this system is prone to interfacial debonding during molding and the initial stages of vulcanization. Furthermore, under high-temperature conditions, the conveyor belt interface is susceptible to thermal degradation, leading to a decrease in the chemical bonding stability between the steel cord core and the core rubber layer, a significant reduction in bonding strength, and resulting in premature damage to the conveyor belt and a shortened service life.

[0004] Therefore, there is an urgent need for a new type of low-smoke, halogen-free steel cord flame-retardant conveyor belt to overcome the current limitations in the use of steel cord conveyor belts and meet the urgent needs of modern industry for safe, efficient, and long-life conveying equipment. Summary of the Invention

[0005] The primary objective of this invention is to provide a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt.

[0006] The second objective of this invention is to provide a method for preparing a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A general-purpose low-smoke halogen-free steel cord flame-retardant conveyor belt, comprising a steel cord core and a core rubber layer, wherein the core rubber layer is located between the cover rubber layer and the steel cord core, and by weight, the core rubber layer comprises the following components: 65-75 parts of EPDM rubber, 10-20 parts of natural rubber, 3-5 parts of tackifying resin, 1.5-2 parts of cobalt salt, 5-8 parts of vulcanizing activator, 1-3 parts of magnesium oxide, 8-15 parts of reinforcing agent, 3-5 parts of poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), 1.5-3 parts of vulcanizing accelerator, 3-5 parts of antioxidant, 1.8-2.5 parts of vulcanizing agent, 1-3 parts of antimony trioxide, 12-20 parts of quaternary flame retardant synergist, 3-5 parts of char-forming flame retardant, and 5-8 parts of softener; The preparation method of the poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) is as follows: 5-vinyl-1H-benzimidazole and N-acryloylmorpholine are added to anhydrous N,N-dimethylacetamide, and then azobisisobutyronitrile is added to react; the reaction solution is concentrated, dialyzed and dried to obtain the product.

[0008] Further, the ratio of 5-vinyl-1H-benzimidazole, N-acryloylmorpholine, anhydrous N,N-dimethylacetamide, and azobisisobutyronitrile is 5g:7-10g:60mL:0.15-0.25g; the reaction temperature is 40-50℃, and the reaction time is 5-8h.

[0009] Furthermore, the preparation process of the vulcanization accelerator is as follows: (1) Add phosphorus pentasulfide to ammonia water, stir evenly, heat to 60-65℃, and then add N-phenyl-2-cyanoacetamide to react; after purification, 2-aminothioyl-N-phenylacetamide is obtained. (2) Add 2-aminothioyl-N-phenylacetamide to anhydrous ethanol, then add sodium, stir evenly, add ethyl 3,3-bis(methylthio)-2-cyanoacrylate to react; after filtration, washing and drying, intermediate 1 is obtained; (3) Stearic acid was added to dichloromethane and stirred until homogeneous. Then triethylamine and ethyl chloroformate were added and stirred until homogeneous. Intermediate 1 was added to react. The reaction mixture was washed, dried, concentrated and purified to obtain intermediate 2. (4) Intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, and tetrasulfonic phthalocyanine zinc are added to water for reaction; the reaction solution is filtered, washed, and dried to obtain the final product.

[0010] Further, in step (1), the ratio of phosphorus pentasulfide, N-phenyl-2-cyanoacetamide, and ammonia is 22-25 mmol: 20 mol: 25-30 mL, and the concentration of ammonia is 25 wt%; the reaction temperature is 40-50℃, and the reaction time is 0.5-2 h; in step (2), the ratio of 2-aminomethylthioyl-N-phenylacetamide, sodium, ethyl 3,3-bis(methylthio)-2-cyanoacrylate, and anhydrous ethanol is 10-12 mmol: 10-12 mmol: 10 mmol: 30 mL; the reaction temperature is 5-10℃, and the reaction time is 2-5 h.

[0011] Further, in step (3), the ratio of stearic acid, triethylamine, ethyl chloroformate, intermediate 1, and dichloromethane is 10-15 mmol: 40-60 mmol: 20-30 mmol: 20 mmol: 30 mL; the reaction temperature is 3-8 °C and the time is 15-45 min.

[0012] Further, in step (4), the ratio of intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, tetrasulfonic phthalocyanine zinc, and water is 10 mmol: 20-30 mmol: 1-2 mmol: 1-2 mmol: 1-2 mmol: 60 mL; the reaction temperature is 70-90 °C, the time is 2-5 h, and the pressure is 1-1.5 MPa.

[0013] Further, the tackifying resin is coumarone-indene resin; the cobalt salt is cobalt borate; the reinforcing agent is silica; the vulcanizing activator is zinc oxide; the antioxidant is NBC antioxidant; the vulcanizing agent is sulfur; the quaternary flame retardant synergist is prepared by mixing zinc borate, montmorillonite, melamine cyanurate, and aluminum diethylphosphonate in a mass ratio of 1:1:3:3; the char-forming flame retardant is pentaerythritol; and the softener is paraffin oil.

[0014] Further, the covering adhesive layer comprises the following raw materials in parts by weight: 65-75 parts of EPDM rubber, 40-50 parts of nitrile rubber, 25-35 parts of quaternary flame retardant synergist, 10-15 parts of reinforcing agent, 10-15 parts of plasticizer, 5-10 parts of vulcanizing agent, 5-10 parts of char-forming flame retardant, 1.5-2 parts of catalyst, 5-7 parts of vulcanization accelerator, 3-5 parts of antioxidant, and 5-10 parts of softener.

[0015] Furthermore, the quaternary flame retardant synergist is prepared by mixing zinc borate, montmorillonite, melamine cyanurate, and aluminum diethylphosphonate in a mass ratio of 1:1:3:3; the reinforcing agent is silica; the plasticizer is stearic acid; the vulcanizing agent is sulfur; the char-forming flame retardant is pentaerythritol; the catalyst is trimethylenediamine; the antioxidant is NBC antioxidant; the softener is paraffin oil; and the vulcanization accelerator is N-cyclohexyl-2-benzothiazole sulfenamide.

[0016] A method for preparing a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt includes the following preparation steps: S1. Weigh the raw materials for the cover rubber layer according to the formula. Mix EPDM rubber and nitrile rubber for 35-45s, then add antioxidant, plasticizer, quaternary flame retardant synergist and carbon-forming flame retardant and mix for 85-95s. Then add reinforcing agent and softener and discharge the rubber at 125-135℃. After the rubber is cooled to room temperature, add vulcanizing agent, accelerator and catalyst and mix. Discharge the rubber at 95-105℃ to obtain the cover rubber layer. S2. Weigh the raw materials for the core rubber layer according to the formula. Mix EPDM rubber and natural rubber for 35-45 seconds, then add tackifying resin, cobalt salt, vulcanizing activator, magnesium oxide, poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), antioxidant, antimony trioxide, quaternary flame retardant synergist, and char-forming flame retardant. Mix evenly and knead at 80-90℃ and 0.35MPa for 3-5 minutes. Then add reinforcing agent and softener and knead at 95-100℃ and 0.35MPa for 5-6 minutes. Finally, add vulcanizing agent and vulcanization accelerator and knead at 85-95℃ and 0.35MPa for 2-3 minutes. Then press the mixture into sheets using a two-roll mill to obtain the core rubber layer. S3. Wrap the core rubber layer around the steel wire rope core, attach the cover rubber layer to the outside of the core rubber layer, press to form a strip blank, vulcanize, and obtain the product.

[0017] Compared with the prior art, the main advantages of the present invention are as follows: 1. This invention provides a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt. The vulcanization accelerator of this invention integrates polar amide, thiocarbamate, and C18 stearyl long chain in its molecular structure. Therefore, it can generate strong chemical adsorption and coordination of metal oxides on the surface of steel wire rope in the initial bonding stage, and reduce interfacial tension with the help of long chains, so that the rubber molecular chains are evenly spread, resulting in good initial bonding strength. Entering the vulcanization stage, the intramolecular thioamino and methylthio groups break first and release abundant active sulfur species, thus forming a dense and uniform cross-linked network. The stearamide segments have high compatibility with rubber hydrocarbons and play a dispersing role, making the filler distribution more uniform. The dihydropyridine skeleton inhibits network degradation by stabilizing free radicals, ensuring the integrity of the cross-linked structure, thereby improving the mechanical properties of the conveyor belt.

[0018] 2. This invention provides a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt. The poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) introduced in the core rubber layer constructs a heat-resistant and oxidation-resistant barrier on the metal side: imidazole forms reversible coordination bonds with morpholine groups and borosilicated cobalt, and the benzene ring generates a weak π- interaction with the coating, which together inhibits interfacial slippage, thereby ensuring that the metal coating locks the core rubber layer at high temperatures and giving the core rubber a long-lasting and flexible adhesive strength; the hydrogen bonds formed between benzimazole N–H and the flame-retardant components break and absorb heat when heated, and regenerate after cooling, which can simultaneously improve the flame retardancy and toughness of the conveyor belt.

[0019] 3. The present invention also provides a method for preparing a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt. The preparation method is simple and has practical value in actual production. Attached Figure Description

[0020] Figure 1 The infrared spectrum of poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) obtained in Example 1 of this invention is shown. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0022] The ethylene propylene diene monomer (EPDM) rubber of this invention has an ethylene content of 50%~60% and a Mooney viscosity of 40~50; the natural rubber is the No. 1 standard rubber of Hainan Natural Rubber Industry Group Co., Ltd.; the tackifying resin is coumarone-indene resin; the cobalt salt is cobalt borate; the reinforcing agent is silica; the vulcanizing activator is zinc oxide; the antioxidant is NBC antioxidant; the vulcanizing agent is sulfur; the quaternary flame retardant synergist is prepared by mixing zinc borate, montmorillonite (nano-silicate), melamine cyanurate (nitrogen-based flame retardant), and aluminum diethylphosphinate (phosphorus-based flame retardant) in a mass ratio of 1:1:3:3; the carbon-forming flame retardant is pentaerythritol; the softener is paraffin oil; the plasticizer is stearic acid; the catalyst is trimethylenediamine; and the acrylonitrile butadiene rubber has an acrylonitrile content of 34%-37% and a Mooney viscosity of 40-50.

[0023] Example 1 A general-purpose low-smoke halogen-free steel cord flame-retardant conveyor belt includes a steel cord core, a core rubber layer wrapped around the steel cord core, and a cover rubber layer covering the core rubber layer. By weight, the core rubber layer comprises the following components: 70 parts EPDM rubber, 15 parts natural rubber, 4 parts tackifying resin, 1.8 parts cobalt salt, 7 parts vulcanizing activator, 2 parts magnesium oxide, 12 parts reinforcing agent, 4 parts poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), 2 parts vulcanizing accelerator, 4 parts antioxidant, 2.3 parts vulcanizing agent, 2 parts antimony trioxide, 16 parts quaternary flame retardant synergist, 4 parts char-forming flame retardant, and 6 parts softener. The adhesive layer in this embodiment comprises the following raw materials in parts by weight: 70 parts of EPDM rubber, 45 parts of nitrile rubber, 30 parts of quaternary flame retardant synergist, 13 parts of reinforcing agent, 13 parts of plasticizer, 8 parts of vulcanizing agent, 8 parts of char-forming flame retardant, 1.8 parts of catalyst, 6 parts of vulcanization accelerator (N-cyclohexyl-2-benzothiazole sulfenamide), 4 parts of antioxidant, and 8 parts of softener.

[0024] The preparation method of poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) in the core adhesive layer is as follows: 5-vinyl-1H-benzimidazole and N-acryloylmorpholine are added to anhydrous N,N-dimethylacetamide, and then azobisisobutyronitrile is added. The ratio of 5-vinyl-1H-benzimidazole, N-acryloylmorpholine, anhydrous N,N-dimethylacetamide, and azobisisobutyronitrile is controlled at 5g:8g:60mL:0.2g. Then, the reaction is carried out at 45℃ for 7h under a nitrogen atmosphere. After the reaction solution is concentrated to remove the solvent, it is dialyzed in deionized water for 60h and then freeze-dried to obtain the product.

[0025] The preparation process of the vulcanization accelerator in the core layer is as follows: (1) Add phosphorus pentasulfide to 25wt% ammonia water, stir evenly and heat to 60℃, then add N-phenyl-2-cyanoacetamide, wherein the ratio of phosphorus pentasulfide, N-phenyl-2-cyanoacetamide and ammonia water is 24mmol:20mol:25mL; after the addition is completed, cool to 45℃ and react for 1h; cool the reaction solution to room temperature, extract the reaction solution with ethyl acetate, and purify the organic phase by drying, concentration and silica gel column chromatography (ethyl acetate / petroleum ether = 1:5, v / v, eluent) to obtain 2-aminomethylthioyl-N-phenylacetamide; 1 ¹H NMR (400 MHz, DMSO): δ 10.03 (s, 1H), 9.50 (s, 2H), 7.61 (d, 2H), 7.30 (t, 2H), 7.04 (t, 1H), 3.67 (s, 2H); ESI: calculated m / z value is C9H.10 N2OS [M+H] + : 195.05, Measured value: 195.05.

[0026] (2) Add 2-aminothioyl-N-phenylacetamide to anhydrous ethanol, then add sodium, stir evenly and cool to 0°C, then add ethyl 3,3-bis(methylthio)-2-cyanoacrylate, wherein the ratio of 2-aminothioyl-N-phenylacetamide, sodium, ethyl 3,3-bis(methylthio)-2-cyanoacrylate and anhydrous ethanol is 11 mmol: 11 mmol: 10 mmol: 30 mL; stir evenly and heat to 8°C for 4 h; filter the reaction solution, wash the filter cake with ethanol and hexane, and dry to obtain intermediate 1; 1 ¹H NMR (400 MHz, DMSO): δ 9.73 (s, 1H), 7.58 (d, 2H), 7.27 (t, 2H), 7.04 (t, 1H), 6.50 (s, 2H), 5.38 (s, 2H), 4.37 (s, 1H), 4.18 (q, 2H), 2.75 (s, 3H), 1.28 (t, 3H); ESI mass spectrometry: calculated m / z value is C0. 16 H 19 N3O3S2 [M+H] + : 366.09, measured value: 366.07.

[0027] (3) Stearic acid was added to dichloromethane, stirred evenly, and cooled to 0°C. Triethylamine was then added, followed by ethyl chloroformate. After stirring evenly, intermediate 1 was added. The ratio of stearic acid, triethylamine, ethyl chloroformate, intermediate 1, and dichloromethane was 13 mmol: 50 mmol: 25 mmol: 20 mmol: 30 mL. The reaction was carried out at 5°C for 30 min. The reaction mixture was washed successively with 1 M hydrochloric acid, 0.5 M sodium bicarbonate aqueous solution, and deionized water. The dichloromethane phase was dried, concentrated, and purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:8, v / v, eluent) to obtain intermediate 2. 1¹H NMR (400 MHz, DMSO): δ 9.73 (s, 1H), 9.21 (s, 1H), 7.58 (d, 2H), 7.27 (t, 2H), 7.04 (t, 1H), 5.38 (s, 2H), 4.37 (s, 1H), 4.18 (q, 2H), 2.75 (s, 3H), 2.32 (t, 2H), 1.53 (t, 2H), 1.31–1.26 (m, 31H), 0.89 (t, 3H); ESI mass spectrometry: calculated m / z value is C 34 H 53 N3O4S2 [M+H] + : 633.35, measured value: 633.36.

[0028] (4) Add intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, and tetrasulfonic phthalocyanine zinc to water, wherein the ratio of intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, tetrasulfonic phthalocyanine zinc, and water is 10 mmol: 25 mmol: 1.5 mmol: 1.5 mmol: 1.5 mmol: 60 mL; then heat to 80 °C, pressurize with air, and the pressure inside the reactor is 1.0 MPa. React for 4 h; cool the reaction solution to room temperature, filter, wash the filter cake with water, and dry the filter cake to obtain the sulfidation accelerator.

[0029] 1 ¹H NMR (400MHz, DMSO): δ 9.73 (s, 1H), 9.21 (s, 1H), 7.58 (d, 2H), 7.27 (t, 2H), 7.04 (t, 1H), 5.38 (s, 2H), 4.35 (s, 1H), 4.18 (q, 2H), 2.75 (s, 3H), 2.61 (q, 1H), 2.32 (t, 2H), 1.75–1.45 (m, 8H), 1.31–1.12 (m, 35H), 0.89 (t, 3H); ESI: calculated m / z value is C0. 40 H 64 N4O4S2 [M+H] + : 729.44, Measured value: 729.44.

[0030] A method for preparing a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt includes the following preparation steps: S1. Weigh each raw material for the cover rubber layer according to the formula. Mix EPDM rubber and nitrile rubber for 40 seconds, then add antioxidant, plasticizer, quaternary flame retardant synergist and carbon-forming flame retardant and mix for 90 seconds. Then add reinforcing agent and softener and discharge the rubber at 130°C. After the rubber is cooled to room temperature, add vulcanizing agent, vulcanization accelerator and catalyst and mix. Discharge the rubber at 100°C to obtain the cover rubber layer. S2. Weigh the raw materials for the core rubber layer according to the formula. Mix EPDM rubber and natural rubber for 40 seconds, then add tackifying resin, cobalt salt, vulcanizing activator, magnesium oxide, poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), antioxidant, antimony trioxide, quaternary flame retardant synergist, and char-forming flame retardant. Mix evenly and knead at 85℃ and 0.35MPa for 4 minutes. Then add reinforcing agent and softener and knead at 95℃ and 0.35MPa for 5.5 minutes. Finally, add vulcanizing agent and vulcanization accelerator and knead at 90℃ and 0.35MPa for 2.5 minutes. Then press the mixture into sheets using a two-roll mill to obtain the core rubber layer. S3. Wrap a core rubber layer around the outside of the wire rope core, and then attach a cover rubber layer to the outside of the core rubber layer. Press the cover rubber layer on a cold press to form a strip blank, and vulcanize it at 145°C for 25 minutes to obtain the product.

[0031] Example 2 A general-purpose low-smoke halogen-free steel cord flame-retardant conveyor belt includes a steel cord core, a core rubber layer wrapped around the steel cord core, and a cover rubber layer covering the core rubber layer. By weight, the core rubber layer comprises the following components: 65 parts EPDM rubber, 10 parts natural rubber, 3 parts tackifying resin, 1.5 parts cobalt salt, 5 parts vulcanizing activator, 1 part magnesium oxide, 8 parts reinforcing agent, 3 parts poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), 1.5 parts vulcanizing accelerator, 3 parts antioxidant, 1.8 parts vulcanizing agent, 1 part antimony trioxide, 12 parts quaternary flame retardant synergist, 3 parts char-forming flame retardant, and 5 parts softener. The adhesive layer in this embodiment comprises the following raw materials in parts by weight: 65 parts of EPDM rubber, 40 parts of nitrile rubber, 25 parts of quaternary flame retardant synergist, 10 parts of reinforcing agent, 10 parts of plasticizer, 5 parts of vulcanizing agent, 5 parts of char-forming flame retardant, 1.5 parts of catalyst, 5 parts of vulcanization accelerator (N-cyclohexyl-2-benzothiazole sulfenamide), 3 parts of antioxidant, and 5 parts of softener.

[0032] The preparation method of poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) in the core adhesive layer is as follows: 5-vinyl-1H-benzimidazole and N-acryloylmorpholine are added to anhydrous N,N-dimethylacetamide, and then azobisisobutyronitrile is added. The ratio of 5-vinyl-1H-benzimidazole, N-acryloylmorpholine, anhydrous N,N-dimethylacetamide, and azobisisobutyronitrile is controlled at 5g:7g:60mL:0.15g. Then, the reaction is carried out at 40℃ for 8h under a nitrogen atmosphere. After the reaction solution is concentrated to remove the solvent, it is dialyzed in deionized water for 48h and then freeze-dried to obtain the product.

[0033] The preparation process of the vulcanization accelerator in the core layer is as follows: (1) Phosphorus pentasulfide was added to 25wt% ammonia water, stirred evenly, and then heated to 65℃. N-phenyl-2-cyanoacetamide was then added, with the ratio of phosphorus pentasulfide, N-phenyl-2-cyanoacetamide, and ammonia water being 22mmol:20mol:25mL. After the addition was complete, the temperature was lowered to 40℃ and reacted for 2 hours. The reaction solution was cooled to room temperature, and the reaction solution was extracted with ethyl acetate. The organic phase was dried, concentrated, and purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:5, v / v, eluent) to obtain 2-aminomethylthioyl-N-phenylacetamide. 1 H NMR and (ESI): m / z results are the same as in Example 1.

[0034] (2) Add 2-aminothioyl-N-phenylacetamide to anhydrous ethanol, then add sodium, stir until homogeneous, cool to 0°C, then add ethyl 3,3-bis(methylthio)-2-cyanoacrylate, wherein the ratio of 2-aminothioyl-N-phenylacetamide, sodium, ethyl 3,3-bis(methylthio)-2-cyanoacrylate, and anhydrous ethanol is 10 mmol: 10 mmol: 10 mmol: 30 mL; stir until homogeneous, then heat to 5°C and react for 5 h; filter the reaction solution, wash the filter cake with ethanol and hexane, and dry to obtain intermediate 1; intermediate 1 1 H NMR and (ESI): m / z results are the same as in Example 1.

[0035] (3) Stearic acid was added to dichloromethane, stirred until homogeneous, and then cooled to 0°C. Triethylamine was then added, followed by ethyl chloroformate. After stirring until homogeneous, intermediate 1 was added. The ratio of stearic acid, triethylamine, ethyl chloroformate, intermediate 1, and dichloromethane was 10 mmol: 40 mmol: 20 mmol: 20 mmol: 30 mL. The reaction mixture was reacted at 3°C ​​for 45 min. The reaction mixture was washed sequentially with 1 M hydrochloric acid, 0.5 M sodium bicarbonate aqueous solution, and deionized water. The dichloromethane phase was dried, concentrated, and purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:8, v / v, eluent) to obtain intermediate 2.1 H NMR and (ESI): m / z results are the same as in Example 1.

[0036] (4) Intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, and tetrasulfonic phthalocyanine zinc were added to water, wherein the ratio of intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, tetrasulfonic phthalocyanine zinc, and water was 10 mmol: 20 mmol: 1 mmol: 1 mmol: 1 mmol: 60 mL; then the temperature was raised to 70 °C, air was introduced, the pressure inside the reactor was 1.0 MPa, and the reaction was carried out for 5 h; the reaction solution was cooled to room temperature, filtered, the filter cake was washed with water, and the filter cake was dried to obtain the vulcanization accelerator. The vulcanization accelerator 1 H NMR and (ESI): m / z results are the same as in Example 1.

[0037] A method for preparing a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt includes the following preparation steps: S1. Weigh the raw materials for the cover rubber layer according to the formula. Mix EPDM rubber and nitrile rubber for 35s, then add antioxidant, plasticizer, quaternary flame retardant synergist and carbon-forming flame retardant and mix for 85s. Then add reinforcing agent and softener and discharge the rubber at 125℃. After the rubber is cooled to room temperature, add vulcanizing agent, accelerator and catalyst and mix. Discharge the rubber at 95℃ to obtain the cover rubber layer. S2. Weigh the raw materials for the core rubber layer according to the formula. Mix EPDM rubber and natural rubber for 35 seconds, then add tackifying resin, cobalt salt, vulcanizing activator, magnesium oxide, poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), antioxidant, antimony trioxide, quaternary flame retardant synergist, and char-forming flame retardant. Mix evenly and knead at 80℃ and 0.35MPa for 5 minutes. Then add reinforcing agent and softener and knead at 95℃ and 0.35MPa for 6 minutes. Finally, add vulcanizing agent and vulcanization accelerator and knead at 85℃ and 0.35MPa for 3 minutes. Then press the mixture into sheets using a two-roll mill to obtain the core rubber layer. S3. Wrap a core rubber layer around the outside of the wire rope core, then attach a cover rubber layer to the outside of the core rubber layer and press it on a cold press to form a strip blank. Vulcanize at 140℃ for 30 minutes to obtain the product.

[0038] Example 3 A general-purpose low-smoke halogen-free steel cord flame-retardant conveyor belt includes a steel cord core, a core rubber layer wrapped around the steel cord core, and a cover rubber layer covering the core rubber layer. By weight, the core rubber layer comprises the following components: 75 parts EPDM rubber, 20 parts natural rubber, 5 parts tackifying resin, 2 parts cobalt salt, 8 parts vulcanizing activator, 3 parts magnesium oxide, 15 parts reinforcing agent, 5 parts poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), 3 parts vulcanizing accelerator, 5 parts antioxidant, 2.5 parts vulcanizing agent, 3 parts antimony trioxide, 20 parts quaternary flame retardant synergist, 5 parts char-forming flame retardant, and 8 parts softener. The adhesive layer in this embodiment comprises the following raw materials in parts by weight: 75 parts of EPDM rubber, 50 parts of nitrile rubber, 35 parts of quaternary flame retardant synergist, 15 parts of reinforcing agent, 15 parts of plasticizer, 10 parts of vulcanizing agent, 10 parts of char-forming flame retardant, 2 parts of catalyst, 7 parts of vulcanization accelerator (N-cyclohexyl-2-benzothiazole sulfenamide), 5 parts of antioxidant, and 10 parts of softener.

[0039] The preparation method of poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) in the core adhesive layer is as follows: 5-vinyl-1H-benzimidazole and N-acryloylmorpholine are added to anhydrous N,N-dimethylacetamide, and then azobisisobutyronitrile is added. The ratio of 5-vinyl-1H-benzimidazole, N-acryloylmorpholine, anhydrous N,N-dimethylacetamide, and azobisisobutyronitrile is controlled at 5g:10g:60mL:0.25g. Then, the reaction is carried out at 50℃ for 5h under a nitrogen atmosphere. After the reaction solution is concentrated to remove the solvent, it is dialyzed in deionized water for 72h and then freeze-dried to obtain the product.

[0040] The preparation process of the vulcanization accelerator in the core layer is as follows: (1) Phosphorus pentasulfide was added to 25wt% ammonia water, stirred evenly, and then heated to 65℃. N-phenyl-2-cyanoacetamide was then added, with the ratio of phosphorus pentasulfide, N-phenyl-2-cyanoacetamide, and ammonia water being 25mmol:20mol:30mL. After the addition was complete, the temperature was lowered to 50℃ and the reaction was carried out for 0.5h. The reaction solution was cooled to room temperature, and the reaction solution was extracted with ethyl acetate. The organic phase was dried, concentrated, and purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:5, v / v, eluent) to obtain 2-aminomethylthioyl-N-phenylacetamide. 1 H NMR and (ESI): m / z results are the same as in Example 1.

[0041] (2) 2-Aminothioyl-N-phenylacetamide was added to anhydrous ethanol, followed by sodium. After stirring until homogeneous, the mixture was cooled to 0°C. Then, ethyl 3,3-bis(methylthio)-2-cyanoacrylate was added, wherein the ratio of 2-aminothioyl-N-phenylacetamide, sodium, ethyl 3,3-bis(methylthio)-2-cyanoacrylate, and anhydrous ethanol was 12 mmol:12 mmol:10 mmol:30 mL. After stirring until homogeneous, the mixture was heated to 10°C and reacted for 2 h. The reaction solution was filtered, and the filter cake was washed with ethanol and hexane and dried to obtain intermediate 1. Intermediate 1 was prepared by... 1 H NMR and (ESI): m / z results are the same as in Example 1.

[0042] (3) Stearic acid was added to dichloromethane, stirred until homogeneous, and then cooled to 0°C. Triethylamine was then added, followed by ethyl chloroformate. After stirring until homogeneous, intermediate 1 was added. The ratio of stearic acid, triethylamine, ethyl chloroformate, intermediate 1, and dichloromethane was 15 mmol: 60 mmol: 30 mmol: 20 mmol: 30 mL. The reaction mixture was reacted at 8°C for 15 min. The reaction mixture was washed sequentially with 1 M hydrochloric acid, 0.5 M sodium bicarbonate aqueous solution, and deionized water. The dichloromethane phase was dried, concentrated, and purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:8, v / v, eluent) to obtain intermediate 2. Intermediate 2 was prepared by... 1 H NMR and (ESI): m / z results are the same as in Example 1.

[0043] (4) Intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, and tetrasulfonic phthalocyanine zinc were added to water, wherein the ratio of intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, tetrasulfonic phthalocyanine zinc, and water was 10 mmol: 30 mmol: 2 mmol: 2 mmol: 2 mmol: 60 mL; then the temperature was raised to 90 °C, air was introduced, the pressure inside the reactor was 1.0 MPa, and the reaction was carried out for 2 h; the reaction solution was cooled to room temperature, filtered, the filter cake was washed with water, and the filter cake was dried to obtain the vulcanization accelerator. 1 H NMR and (ESI): m / z results are the same as in Example 1.

[0044] A method for preparing a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt includes the following preparation steps: S1. Weigh the raw materials for the cover rubber layer according to the formula. Mix EPDM rubber and nitrile rubber for 45s, then add antioxidant, plasticizer, quaternary flame retardant synergist and carbon-forming flame retardant and mix for 95s. Then add reinforcing agent and softener and discharge the rubber at 135℃. After the rubber is cooled to room temperature, add vulcanizing agent, accelerator and catalyst and mix. Discharge the rubber at 105℃ to obtain the cover rubber layer. S2. Weigh the raw materials for the core rubber layer according to the formula. Mix EPDM rubber and natural rubber for 45 seconds, then add tackifying resin, cobalt salt, vulcanizing activator, magnesium oxide, poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), antioxidant, antimony trioxide, quaternary flame retardant synergist, and char-forming flame retardant. Mix evenly and knead at 90℃ and 0.35MPa for 3 minutes. Then add reinforcing agent and softener and knead at 100℃ and 0.35MPa for 5 minutes. Finally, add vulcanizing agent and vulcanization accelerator and knead at 95℃ and 0.35MPa for 2 minutes. Then press the mixture into sheets using a two-roll mill to obtain the core rubber layer. S3. Wrap a core rubber layer around the outside of the wire rope core, then attach a cover rubber layer to the outside of the core rubber layer and press it on a cold press to form a strip blank. Vulcanize at 150°C for 20 minutes to obtain the product.

[0045] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) is omitted from the core adhesive layer.

[0046] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the vulcanization accelerator is omitted from the core adhesive layer.

[0047] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the vulcanization accelerator in the core layer is replaced with an equal amount of N-cyclohexyl-2-benzothiazole sulfenamide.

[0048] Experimental Example 1 The infrared spectrum of poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) obtained in Example 1 of this invention is as follows: Figure 1 As shown. At 3300cm -1 The characteristic peak is attributed to the stretching vibration of the -NH bond on the benzimidazole ring; 3004 cm⁻¹ -1 The characteristic peak is attributed to the stretching vibration of the Ar-H bond on the aromatic ring; 2936 cm⁻¹ -1 The characteristic peak is attributed to the stretching vibration of the CH bond in the saturated methylene group on the morpholine ring; 1643 cm⁻¹ -1 The characteristic peak is attributed to the stretching vibration of the C=O bond in the amide bond; 1608 cm⁻¹ -1 The characteristic peak is attributed to the C=C stretching vibration of the benzene ring skeleton; 1540 cm⁻¹ -1 The characteristic peak is attributed to the bending vibration of the -NH bond in the benzimidazole ring; 1360 cm⁻¹ -1 The characteristic peak is attributed to the stretching vibration of the COC bond in the morpholine ring; 750 cm⁻¹ -1 The characteristic peaks are attributed to the bending vibrations of the -CH2- bonds on the morpholine ring.

[0049] Experimental Example 2 To investigate the performance of the flame-retardant conveyor belts obtained in Examples 1-3 and Comparative Examples 1-3 of the present invention, the following tests were conducted: 1. The flame retardant properties, tensile strength, bonding strength of the steel wire rope before aging, and bonding strength of the steel wire rope after aging (treated at 70℃ for 168h) were all measured in accordance with the standard MT / T668-2019 "Flame-retardant conveyor belt with steel wire rope core for coal mine".

[0050] 2. Smoke density was tested according to GB / T8323.2-2008 "Plastic Smoke Generation Part 2: Test Method for Determination of Smoke Density by Single Chamber Method". The test mode was 25kW / m³. 2 Calculate the specific optical density value Ds4 at 4 minutes for irradiance and flame combustion.

[0051] 3. The toxicity index was implemented according to the standard EN45545.2; the gas concentration was collected at the 4th minute, and the CIT4 value was calculated. The above test results are shown in Table 1.

[0052] Table 1 As shown in Table 1, the conveyor belt obtained by this invention not only possesses good tensile strength and excellent wire rope bonding strength, but also maintains a high level of wire rope bonding strength after aging. Furthermore, the alcohol torch burning test of the conveyor belt shows that it still exhibits excellent flame-retardant properties after the covering adhesive layer is removed. In addition, the conveyor belt formulation of this invention does not contain halogenated flame retardants and has low specific optical density and toxicity index, proving that the conveyor belt of this invention has low-smoke, halogen-free, and flame-retardant characteristics. Among these, the performance of Examples 1-3 is superior to that of Comparative Examples 1-3.

[0053] Compared to Example 1, Comparative Example 1 omits the poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) in the core layer; its adhesive strength and aging resistance deteriorate, and its flame retardant properties are also reduced. This is because the benzimidazole structure and flame-retardant components of poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) synergistically improve the flame retardancy of the conveyor belt. Compared to Example 1, Comparative Example 2 omits the vulcanization accelerator in the core layer; its tensile strength and adhesive strength are both reduced, indicating that the vulcanization accelerator has a promoting effect on improving both adhesive strength and the mechanical properties of the conveyor belt. Compared to Example 1, Comparative Example 3 replaces the vulcanization accelerator in the core layer with an equal amount of N-cyclohexyl-2-benzothiazole sulfenamide. Its tensile strength and adhesive strength are both inferior to those of Example 1. This demonstrates that traditional vulcanization accelerators (N-cyclohexyl-2-benzothiazole sulfenamide) are inferior to the functionalized vulcanization accelerator with a specific structure designed and synthesized in this invention in terms of improving the mechanical and adhesive strength of conveyor belts.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt, comprising a steel wire rope core, a core rubber layer wrapped around the steel wire rope core, and a cover rubber layer covering the core rubber layer; characterized in that, The core layer comprises the following components by weight: 65-75 parts EPDM rubber, 10-20 parts natural rubber, 3-5 parts tackifying resin, 1.5-2 parts cobalt salt, 5-8 parts vulcanizing activator, 1-3 parts magnesium oxide, 8-15 parts reinforcing agent, 3-5 parts poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), 1.5-3 parts vulcanizing accelerator, 3-5 parts antioxidant, 1.8-2.5 parts vulcanizing agent, 1-3 parts antimony trioxide, 12-20 parts quaternary flame retardant synergist, 3-5 parts char-forming flame retardant, and 5-8 parts softener. The preparation method of the poly(5-vinylbenzimidazole-co-N-acryloylmorpholine) is as follows: 5-vinyl-1H-benzimidazole and N-acryloylmorpholine are added to anhydrous N,N-dimethylacetamide, and then azobisisobutyronitrile is added to react; the reaction solution is concentrated, dialyzed and dried to obtain the product.

2. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 1, characterized in that, The ratio of 5-vinyl-1H-benzimidazole, N-acryloylmorpholine, anhydrous N,N-dimethylacetamide, and azobisisobutyronitrile is 5g:7-10g:60mL:0.15-0.25g; the reaction temperature is 40-50℃ and the reaction time is 5-8h.

3. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 1, characterized in that, The preparation process of the vulcanization accelerator is as follows: (1) Add phosphorus pentasulfide to ammonia water, stir evenly, heat to 60-65℃, and then add N-phenyl-2-cyanoacetamide to react; after purification, 2-aminothioyl-N-phenylacetamide is obtained. (2) Add 2-aminothioyl-N-phenylacetamide to anhydrous ethanol, then add sodium, stir evenly, add ethyl 3,3-bis(methylthio)-2-cyanoacrylate to react; after filtration, washing and drying, intermediate 1 is obtained; (3) Stearic acid was added to dichloromethane and stirred until homogeneous. Then triethylamine and ethyl chloroformate were added and stirred until homogeneous. Intermediate 1 was added to react. The reaction mixture was washed, dried, concentrated and purified to obtain intermediate 2. (4) Intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, and tetrasulfonic phthalocyanine zinc are added to water for reaction; the reaction solution is filtered, washed, and dried to obtain the final product.

4. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 3, characterized in that, In step (1), the ratio of phosphorus pentasulfide, N-phenyl-2-cyanoacetamide, and ammonia is 22-25 mmol: 20 mol: 25-30 mL, and the concentration of ammonia is 25 wt%. The reaction temperature is 40-50℃ and the reaction time is 0.5-2 h. In step (2), the ratio of 2-aminomethylthioyl-N-phenylacetamide, sodium, ethyl 3,3-bis(methylthio)-2-cyanoacrylate, and anhydrous ethanol is 10-12 mmol: 10-12 mmol: 10 mmol: 30 mL. The reaction temperature is 5-10℃ and the reaction time is 2-5 h.

5. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 3, characterized in that, In step (3), the ratio of stearic acid, triethylamine, ethyl chloroformate, intermediate 1, and dichloromethane is 10-15 mmol: 40-60 mmol: 20-30 mmol: 20 mmol: 30 mL; the reaction temperature is 3-8 °C and the reaction time is 15-45 min.

6. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 3, characterized in that, In step (4), the ratio of intermediate 2, cyclohexylamine, (4',4'',4'''-tetrasulfonic phthalocyanine)cobalt, tetracarboxylated phthalocyanine copper, tetrasulfonic phthalocyanine zinc, and water is 10 mmol: 20-30 mmol: 1-2 mmol: 1-2 mmol: 1-2 mmol: 60 mL; the reaction temperature is 70-90 °C, the time is 2-5 h, and the pressure is 1-1.5 MPa.

7. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 1, characterized in that, The tackifying resin is coumarone-indene resin; the cobalt salt is cobalt borate; the reinforcing agent is silica; the vulcanizing activator is zinc oxide; the antioxidant is NBC antioxidant; the vulcanizing agent is sulfur; the quaternary flame retardant synergist is prepared by mixing zinc borate, montmorillonite, melamine cyanurate, and aluminum diethylphosphonate in a mass ratio of 1:1:3:3; the char-forming flame retardant is pentaerythritol; and the softener is paraffin oil.

8. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 1, characterized in that, The covering adhesive layer comprises the following raw materials in parts by weight: 65-75 parts of EPDM rubber, 40-50 parts of nitrile rubber, 25-35 parts of quaternary flame retardant synergist, 10-15 parts of reinforcing agent, 10-15 parts of plasticizer, 5-10 parts of vulcanizing agent, 5-10 parts of char-forming flame retardant, 1.5-2 parts of catalyst, 5-7 parts of vulcanization accelerator, 3-5 parts of antioxidant, and 5-10 parts of softener.

9. The general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to claim 8, characterized in that, The quaternary flame retardant synergist is prepared by mixing zinc borate, montmorillonite, melamine cyanurate, and aluminum diethylphosphonate in a mass ratio of 1:1:3:3; the reinforcing agent is silica; the plasticizer is stearic acid; the vulcanizing agent is sulfur; the char-forming flame retardant is pentaerythritol; the catalyst is trimethylenediamine; the antioxidant is NBC antioxidant; the softener is paraffin oil; and the vulcanization accelerator is N-cyclohexyl-2-benzothiazole sulfenamide.

10. The method for preparing a general-purpose low-smoke halogen-free steel wire rope core flame-retardant conveyor belt according to any one of claims 1-9, characterized in that, The preparation steps include the following: S1. Weigh the raw materials for the cover rubber layer according to the formula. Mix EPDM rubber and nitrile rubber for 35-45s, then add antioxidant, plasticizer, quaternary flame retardant synergist and carbon-forming flame retardant and mix for 85-95s. Then add reinforcing agent and softener and discharge the rubber at 125-135℃. After the rubber is cooled to room temperature, add vulcanizing agent, vulcanization accelerator and catalyst and mix. Discharge the rubber at 95-105℃ to obtain the cover rubber layer. S2. Weigh the raw materials for the core rubber layer according to the formula. Mix EPDM rubber and natural rubber for 35-45 seconds, then add tackifying resin, cobalt salt, vulcanizing activator, magnesium oxide, poly(5-vinylbenzimidazole-co-N-acryloylmorpholine), antioxidant, antimony trioxide, quaternary flame retardant synergist, and char-forming flame retardant. Mix evenly and knead at 80-90℃ and 0.35MPa for 3-5 minutes. Then add reinforcing agent and softener and knead at 95-100℃ and 0.35MPa for 5-6 minutes. Finally, add vulcanizing agent and vulcanization accelerator and knead at 85-95℃ and 0.35MPa for 2-3 minutes. Then press the mixture into sheets using a two-roll mill to obtain the core rubber layer. S3. Wrap the core rubber layer around the steel wire rope core, attach the cover rubber layer to the outside of the core rubber layer, press to form a strip blank, vulcanize, and obtain the product.

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