Flame-retardant heat-resistant conveying belt and preparation method thereof

Abstract

The invention belongs to the technical field of conveying belts, and particularly relates to a flame-retardant heat-resistant conveying belt and a preparation method thereof. The flame-retardant heat-resistant conveying belt comprises a framework layer and a covering rubber layer, and the covering rubber layer comprises the following components: ethylene propylene diene monomer, nitrile rubber, flame-retardant resin, a reinforcing agent, a nano flame retardant, an accelerant, an anti-aging agent and sulfur. The flame-retardant resin is used as a part of flame retardant to replace a traditional flame retardant to be added into the covering rubber, so that the influence of the dosage of the flame retardant on the mechanical property of the covering rubber is reduced; bisphenol A-bis (diphenyl phosphate) modified nano aluminum hydroxide is adopted as a nano flame retardant to be added into the covering rubber, so that the compatibility of the nano aluminum hydroxide and the covering rubber is improved, and meanwhile, the flame-retardant and heat-resistant properties of the covering rubber are improved; 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazole sulfenamide are adopted to jointly form an accelerant, so that the vulcanization efficiency is improved, and the mechanical properties and aging resistance of the covering rubber are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of conveyor belts, and particularly relates to a flame-retardant and heat-resistant conveyor belt and a preparation method thereof. Background Art

[0002] Conveyor belts are the core equipment connecting various production nodes in the coal industry, carrying out crucial tasks from mining and washing to transportation. Due to the flammable, high-temperature, and dusty nature of the coal production environment, conventional conveyor belts struggle to meet safety and durability requirements. Flame-retardant and heat-resistant conveyor belts have emerged as crucial equipment for ensuring safe production in the coal industry.

[0003] Currently, most heat-resistant conveyor belts on the market lack flame retardancy, posing a safety hazard when conveying materials at high temperatures or even with open flames. To improve their flame retardancy, some belts incorporate large amounts of flame retardants into their raw materials. However, the addition of large amounts of flame retardants can degrade the performance of the belt cover rubber, reducing elongation and causing increased wear. In particular, a significant decrease in the wear resistance of the belt cover rubber can shorten the belt's service life. Therefore, it is necessary to develop a new flame-retardant and heat-resistant conveyor belt to address the technical issues currently associated with existing conveyor belts.

[0004] A Chinese patent application document, publication number CN117165009A, discloses a flame-retardant and antistatic conveyor belt covering rubber, comprising polyvinyl chloride resin, powdered nitrile rubber, chlorinated polyethylene, an organotin stabilizer, stearic acid, carbon black, a liquid antistatic agent, dioctyl phthalate, an organic flame retardant, and an inorganic flame retardant. This formulation incorporates a phosphorus-nitrogen flame retardant formed from bis(phthalazinone)phenyl phosphate, which has high heat resistance. Adding this to the polyvinyl chloride resin and powdered nitrile rubber can provide flame retardant and antistatic properties, extending the service life of the conveyor belt covering rubber. However, the dosage of the organic and inorganic flame retardants in the formulation is high, and there is no clear compatibility design with the matrix resin. The inorganic flame retardant is a rigid particle, and when used in excessive amounts, it is unevenly dispersed, resulting in poor interfacial bonding with the matrix and the formation of stress concentration points, which significantly reduces tensile strength and tear strength. Furthermore, excessive amounts of the inorganic flame retardant can also increase the hardness and reduce the elasticity of the rubber compound, increasing the wear rate of the covering rubber and shortening the service life of the conveyor belt. Summary of the Invention

[0005] In order to solve the problem in the prior art that excessive use of flame retardants causes reduced tensile properties and wear resistance of conveyor belts, the present invention provides a flame-retardant and heat-resistant conveyor belt and a preparation method thereof.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A flame-retardant and heat-resistant conveyor belt comprises a skeleton layer and a covering rubber layer, wherein the covering rubber layer comprises the following components and their weight proportions: 50-70 parts of EPDM rubber, 40-50 parts of nitrile rubber, 30-40 parts of flame retardant resin, 10-15 parts of reinforcing agent, 10-20 parts of nano flame retardant, 3-8 parts of accelerator, 5-10 parts of antioxidant, and 5-10 parts of sulfur; The flame retardant resin is prepared by adding phenyltriethoxysilane, p-methylphenyltriethoxysilane and ethanol into a reaction kettle, adding phenyl dichlorophosphate, stirring evenly, heating to 70-80° C. and reacting for 1.5-2 hours, continuously heating to 95-100° C. and reacting for 1.6-2.2 hours, continuously heating to 105-110° C. and reacting for 0.5-1 hour, then performing reduced pressure distillation, and cooling to obtain the flame retardant resin.

[0007] Through the above technical solution, phosphate groups are introduced into the silicone resin structure to form a silicon-phosphorus synergistic flame retardant system. Adding it to the covering rubber effectively improves the flame retardant properties of the covering rubber. The silicon element will be converted into silicon dioxide or silicon oxide char during combustion, forming an inorganic protective layer on the surface of the conveyor belt, isolating oxygen and heat transfer, preventing the spread of flames and further degradation of the substrate. The phosphate group decomposes during combustion to produce acidic substances such as phosphoric acid and polyphosphoric acid. On the one hand, it catalyzes the dehydration and carbonization of the resin and promotes the formation of a carbon layer. On the other hand, the released phosphorus free radicals can capture active free radicals in the combustion chain reaction, and continue gas-phase combustion. At the same time, phenyltriethoxysilane and p-methylphenyltriethoxysilane condense after hydrolysis to form a silicone resin structure with silicon-oxygen bonds as the main chain and phenyl groups as the side chains. It has high rigidity and stability, can reduce the dripping of the melt during combustion, and enhance the flame retardant durability. In addition, the present invention uses flame retardant resin as part of the flame retardant instead of traditional flame retardants added to the covering rubber, which can effectively reduce the impact of the flame retardant dosage on the mechanical properties of the covering rubber, and has stable chemical properties and good compatibility with other organic substances in the covering rubber.

[0008] Furthermore, in the method for preparing the flame retardant resin, the molar ratio of phenyltriethoxysilane, p-methylphenyltriethoxysilane and phenyl dichlorophosphate is 3-5:1:2-3.

[0009] Furthermore, the temperature of the reduced pressure distillation in the preparation method of the flame retardant resin is carried out in stages, namely 100-105°C, 110-115°C, 120-130°C, 140-145°C, and 150-155°C, and the time of the reduced pressure distillation is 30-40min, 25-30min, 25-30min, 25-30min, and 80-90min, respectively.

[0010] In the above technical solution, the solvent in the flame-retardant resin system is removed by adopting the way of staged vacuum distillation, which can effectively control the viscosity rise of the flame-retardant resin, prevent local overheating, give the resin system time to relax, and avoid resin overheating or gelation. At the same time, the staged vacuum distillation can effectively reduce the loss rate of phosphorus in the flame-retardant resin and improve the flame-retardant performance of the flame-retardant resin.

[0011] Further, the preparation method of the nano flame retardant is as follows: nano aluminum hydroxide is added to acetone, ultrasonic dispersion is performed, heating is performed to 65-70℃, bisphenol A-bis(diphenyl phosphate) is added dropwise, stirring reaction is performed for 3-4h, cooling is performed, vacuum distillation is performed, drying is performed, grinding is performed, and the nano flame retardant is obtained.

[0012] In the above technical solution, the phosphorus-oxygen double bond in bisphenol A-bis(diphenyl phosphate) forms a coordination bond with aluminum ions, so that bisphenol A-bis(diphenyl phosphate) is connected to nano aluminum oxide to form a stable covalent bond, forming a double flame-retardant system of inorganic flame-retardant + organic flame-retardant. Nano aluminum oxide undergoes a dehydration reaction at high temperatures, releases crystallization water, absorbs a large amount of heat, reduces the surface temperature of the material, and the released crystallization water becomes steam after being released, which dilutes the oxygen concentration in the combustion area and inhibits the combustion reaction. After dehydration, the nano aluminum oxide particles accumulate on the surface of the material to form a dense inorganic protective layer to block the transfer of heat and oxygen; bisphenol A-bis(diphenyl phosphate) will decompose to produce phosphoric acid substances when burning, which catalyze the polymer to form carbon, and at the same time release phosphorus-based free radicals to inhibit the gas phase combustion reaction. Therefore, the nano flame retardant can have a synergistic effect of physical cooling + chemical inhibition + catalytic carbonization, which can significantly improve the flame-retardant effect of the material.

[0013] Further, the molar ratio of the nano aluminum hydroxide to bisphenol A-bis(diphenyl phosphate) in the preparation method of the nano flame retardant is 3-5:1-2.

[0014] Further, the power of the ultrasonic dispersion in the preparation method of the nano flame retardant is 30-40kHz, the duty cycle is 30%-40%, and the ultrasonic dispersion time is 2-4h.

[0015] Further, the temperature of the vacuum distillation in the preparation method of the nano flame retardant is 60-70℃, and the vacuum distillation time is 40-50min.

[0016] Further, the reinforcing agent is one or more of carbon black, white carbon black, calcium carbonate, kaolin, and talc.

[0017] Through the above technical solution, the addition of the reinforcing agent in the conveyor belt cover rubber can significantly improve the tensile strength of the cover rubber, enhance the tear resistance, resist crack propagation, improve the wear resistance of the conveyor belt, and prolong the service life.

[0018] Furthermore, the accelerator is composed of 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide in a mass ratio of 8-12:5-7.

[0019] In the above scheme, the use of 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide as an accelerator can effectively reduce the vulcanization temperature of the cover rubber, shorten the vulcanization time, improve the vulcanization efficiency, and enhance the mechanical properties and aging resistance of the cover rubber. 2-Mercaptobenzothiazole acts as a vulcanization activation center, promoting the decomposition efficiency of N-cyclohexyl-2-benzothiazolesulfenamide, increasing the number of effective crosslinking points, and simultaneously refining the crosslinking network to avoid localized stress concentration. During the vulcanization process, N-cyclohexyl-2-benzothiazolesulfenamide decomposes to produce active sulfur, which forms stable polysulfide crosslinks with rubber molecules, imparting high tensile strength and elasticity to the vulcanized rubber.

[0020] Furthermore, the antioxidant is one or more of antioxidant 4020, antioxidant 4010NA, microcrystalline wax, antioxidant 168, and antioxidant 1010.

[0021] Furthermore, the skeleton layer is aramid canvas.

[0022] The present invention also provides a method for preparing the flame-retardant and heat-resistant conveyor belt, which is specifically: S1: EPDM rubber, NBR and flame retardant resin are mixed in an internal mixer, and then reinforcing agent, nano flame retardant, accelerator, antioxidant and sulfur are added and mixed to obtain a covering rubber; S2: Impregnating the skeleton layer material in liquid phenolic resin, then heating to 60-80°C, keeping warm for 5-10 minutes, and continuing to heat to 140-160°C, keeping warm for 10-15 minutes to obtain an impregnated skeleton; S3: Compounding the covering rubber obtained in step S1 with the impregnated skeleton obtained in step S2, and then performing a vulcanization treatment to obtain a flame-retardant and heat-resistant conveyor belt.

[0023] Through the above technical solution, the skeleton layer impregnated with liquid phenolic resin is compounded with the covering rubber, which effectively improves the bonding performance between the covering rubber and the skeleton layer and effectively extends the service life of the conveyor belt.

[0024] Furthermore, the blending temperature in step S1 is 140-160°C, and the blending time is 30-50 min; the kneading temperature is 140-160°C, and the kneading time is 20-40 min; the impregnation temperature in step S2 is 40-50°C, and the impregnation time is 0.5-1 min; the vulcanization temperature in step S3 is 150-170°C.

[0025] The fire-retardant heat-resistant conveying belt and the preparation method thereof have the following technical advantages. (1) The fire-retardant resin is used as part of the fire retardant instead of the traditional fire retardant to be added into the covering rubber, so that the influence of the amount of the fire retardant on the mechanical properties of the covering rubber is effectively reduced, and the fire-retardant performance of the covering rubber is improved. (2) The bisphenol A-bis(diphenyl phosphate) modified nano-aluminum hydroxide is used as the nano fire retardant to be added into the covering rubber, so that the compatibility of the nano-aluminum hydroxide with the covering rubber is improved, and the fire-retardant and heat-resistant performance of the covering rubber is effectively improved. (3) The 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazole sulfenamide are used as the accelerators to effectively reduce the vulcanization temperature of the covering rubber, shorten the vulcanization time, improve the vulcanization efficiency, and improve the mechanical properties and aging resistance of the covering rubber. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The infrared spectrum of the fire-retardant resin prepared in Preparation Example 3. DETAILED DESCRIPTION

[0027] The present application will be further described in conjunction with specific examples, but the present application is not limited to the following examples. Those skilled in the art can make various modifications according to the basic idea of the present application, as long as the modifications do not deviate from the basic idea of the present application, and the modifications are within the scope of the present application.

[0028] The raw materials in the present embodiment are all commercially available products.

[0029] Preparation Example 1 The preparation method of the fire-retardant resin is as follows: 3 mol of phenyltriethoxysilane, 1 mol of p-methylphenyltriethoxysilane and 150 mL of ethanol are added into a reaction kettle, 2 mol of phenyldichlorophosphate is added, stirred uniformly, heated to 70℃ for 1.5 h, continuously heated to 95℃ for 1.6 h, continuously heated to 105℃, reacted for 0.5 h, and then subjected to stage-by-stage vacuum distillation (100℃ vacuum distillation for 30 min, 110℃ vacuum distillation for 25 min, 120℃ vacuum distillation for 25 min, 140℃ vacuum distillation for 25 min, and 150℃ vacuum distillation for 80 min), and cooled to obtain the fire-retardant resin.

[0030] Preparation Example 2 The preparation method of the flame retardant resin is as follows: 5 mol of phenyltriethoxysilane, 1 mol of p-methylphenyltriethoxysilane and 150 mL of ethanol are added to a reactor, 3 mol of phenyl dichlorophosphate are added, the mixture is stirred evenly, the temperature is raised to 80°C for reaction for 2 hours, the temperature is further raised to 100°C for reaction for 2.2 hours, the temperature is further raised to 110°C for reaction for 1 hour, and then vacuum distillation is performed in stages (vacuum distillation at 105°C for 40 minutes, vacuum distillation at 115°C for 30 minutes, vacuum distillation at 130°C for 30 minutes, vacuum distillation at 145°C for 30 minutes, and vacuum distillation at 155°C for 90 minutes), and the mixture is cooled to obtain the flame retardant resin.

[0031] Preparation Example 3 The preparation method of the flame retardant resin is as follows: 4.1 mol of phenyltriethoxysilane, 1 mol of p-methylphenyltriethoxysilane and 150 mL of ethanol are added to a reactor, 2.6 mol of phenyl dichlorophosphate is added, and the mixture is stirred evenly. The temperature is raised to 75°C and the reaction is carried out for 1.8 hours. The temperature is further raised to 98°C and the reaction is carried out for 2.0 hours. The temperature is further raised to 107°C and the reaction is carried out for 0.7 hours. The mixture is then subjected to reduced pressure distillation in stages (reduced pressure distillation at 103°C for 35 minutes, reduced pressure distillation at 112°C for 28 minutes, reduced pressure distillation at 125°C for 28 minutes, reduced pressure distillation at 144°C for 27 minutes, and reduced pressure distillation at 154°C for 87 minutes), and cooled to obtain the flame retardant resin.

[0032] Preparation Example 4 The preparation method of the nano flame retardant is as follows: 3 mol of nano aluminum hydroxide is added to 50 mL of acetone, ultrasonically dispersed at 30 kHz for 2 hours (duty cycle of 30%), heated to 65°C, 1 mol of bisphenol A-bis(diphenyl phosphate) is added dropwise, stirred for reaction for 3 hours, cooled, and distilled under reduced pressure at 60°C for 40 minutes, dried, and ground to obtain the nano flame retardant.

[0033] Preparation Example 5 The preparation method of the nano flame retardant is as follows: 5 mol of nano aluminum hydroxide is added to 50 mL of acetone, ultrasonically dispersed at 40 kHz for 4 hours (duty cycle of 40%), heated to 70°C, 2 mol of bisphenol A-bis(diphenyl phosphate) is added dropwise, stirred for reaction for 4 hours, cooled, and distilled under reduced pressure at 70°C for 50 minutes, dried, and ground to obtain the nano flame retardant.

[0034] Preparation Example 6 The preparation method of the nano flame retardant is as follows: 4.2 mol of nano aluminum hydroxide is added to 50 mL of acetone, ultrasonically dispersed at 35 kHz for 3.2 hours (duty cycle of 35%), heated to 68°C, 1.6 mol of bisphenol A-bis(diphenyl phosphate) is added dropwise, stirred for reaction for 3.5 hours, cooled, and distilled under reduced pressure at 65°C for 45 minutes, dried, and ground to obtain the nano flame retardant.

[0035] Example 1 A flame-retardant and heat-resistant conveyor belt comprises an aramid canvas skeleton layer and a covering rubber layer. The covering rubber layer contains the following components, in percentage by weight: 50 parts EPDM rubber, 50 parts nitrile rubber, 30 parts flame-retardant resin, 10 parts reinforcing agent, 20 parts nano-flame retardant, 3 parts accelerator, 5 parts antioxidant 4020, and 5 parts sulfur. The reinforcing agent comprises carbon black and white carbon black in a mass ratio of 1:1; the accelerator comprises 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide in a mass ratio of 8:5. The flame-retardant resin is prepared according to Preparation Example 1, and the nano-flame retardant is prepared according to Preparation Example 4.

[0036] The preparation method of flame retardant and heat resistant conveyor belt is: S1: EPDM rubber, NBR and flame retardant resin were placed in an internal mixer and blended at 140°C for 50 minutes. Then, a reinforcing agent, a nano flame retardant, an accelerator, an antioxidant and sulfur were added and mixed at 140°C for 40 minutes to obtain a covering rubber. S2: The skeleton layer material is immersed in liquid phenolic resin at 40°C for 0.5 min, then heated to 60°C, kept warm for 5 min, and further heated to 140°C, kept warm for 10 min to obtain an impregnated skeleton; S3: Compounding the covering rubber obtained in step S1 with the impregnated skeleton obtained in step S2, and then performing a vulcanization treatment at 150° C. to obtain a flame-retardant and heat-resistant conveyor belt.

[0037] Example 2 A flame-retardant and heat-resistant conveyor belt comprises an aramid canvas skeleton layer and a covering rubber layer. The covering rubber layer contains the following components, in percentage by weight: 70 parts EPDM rubber, 40 parts nitrile rubber, 40 parts flame-retardant resin, 15 parts reinforcing agent, 10 parts nano-flame retardant, 8 parts accelerator, 10 parts antioxidant 4010NA, and 10 parts sulfur. The reinforcing agent comprises carbon black and calcium carbonate in a 1:1 mass ratio; the accelerator comprises 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide in a 12:7 mass ratio. The flame-retardant resin is prepared according to Preparation Example 2, and the nano-flame retardant is prepared according to Preparation Example 5.

[0038] The preparation method of flame retardant and heat resistant conveyor belt is: S1: EPDM rubber, NBR and flame retardant resin were placed in an internal mixer and blended at 160°C for 30 minutes. Then, a reinforcing agent, a nano flame retardant, an accelerator, an antioxidant and sulfur were added and mixed at 160°C for 20 minutes to obtain a covering rubber. S2: The skeleton layer material is immersed in liquid phenolic resin at 50°C for 1 minute, then heated to 80°C, kept warm for 10 minutes, and further heated to 160°C, kept warm for 15 minutes to obtain an impregnated skeleton; S3: Compounding the covering rubber obtained in step S1 with the impregnated skeleton obtained in step S2, and then performing a vulcanization treatment at 170° C. to obtain a flame-retardant and heat-resistant conveyor belt.

[0039] Example 3 A flame-retardant and heat-resistant conveyor belt comprises an aramid canvas skeleton layer and a covering rubber layer. The covering rubber layer contains the following components by weight: 62 parts EPDM rubber, 44 parts nitrile rubber, 37 parts flame-retardant resin, 13 parts reinforcing agent, 18 parts nano-flame retardant, 6 parts accelerator, 168 parts antioxidant, and 8 parts sulfur. The reinforcing agent is composed of silica and kaolin in a 1:1 ratio; the accelerator is composed of 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide in a mass ratio of 11:6. The flame-retardant resin is prepared according to Preparation Example 3, and the nano-flame retardant is prepared according to Preparation Example 6.

[0040] The preparation method of flame retardant and heat resistant conveyor belt is: S1: EPDM rubber, NBR and flame retardant resin were placed in an internal mixer and blended at 150°C for 40 minutes. Then, a reinforcing agent, a nano flame retardant, an accelerator, an antioxidant and sulfur were added and mixed at 150°C for 30 minutes to obtain a covering rubber. S2: The skeleton layer material is immersed in liquid phenolic resin at 45°C for 0.8 min, then heated to 70°C, kept warm for 8 min, and further heated to 150°C, kept warm for 12 min to obtain an impregnated skeleton; S3: Compounding the covering rubber obtained in step S1 with the impregnated skeleton obtained in step S2, and then performing a vulcanization treatment at 160° C. to obtain a flame-retardant and heat-resistant conveyor belt.

[0041] Comparative Example 1 The flame-retardant and heat-resistant conveyor belt and its preparation method in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that an equal amount of nano flame retardant is used instead of flame retardant resin in this comparative example.

[0042] Comparative Example 2 The flame-retardant and heat-resistant conveyor belt and its preparation method in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that an equal amount of flame-retardant resin is used instead of nano flame retardant in this comparative example.

[0043] Comparative Example 3 The flame-retardant and heat-resistant conveyor belt and its preparation method in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that an equal amount of phenyltriethoxysilane is used instead of phenyl dichlorophosphate in the flame-retardant resin in this comparative example.

[0044] Comparative Example 4 The preparation method of the flame-retardant heat-resistant conveyor belt in the present comparative example is similar to that of Example 3, and the difference between the present comparative example and Example 3 is that the molar ratio of the phenyltriethoxysilane, p-methylphenyltriethoxysilane and phenyldichlorophosphate in the preparation method of the flame-retardant resin in the present comparative example is 1:5:7.

[0045] Comparative Example 5 The preparation method of the flame-retardant heat-resistant conveyor belt in the present comparative example is similar to that of Example 3, and the difference between the present comparative example and Example 3 is that the preparation method of the nano flame retardant in the present comparative example uses an equal amount of vinyltrimethoxysilane instead of bisphenol A-bis(diphenyl phosphate).

[0046] Comparative Example 6 The preparation method of the flame-retardant heat-resistant conveyor belt in the present comparative example is similar to that of Example 3, and the difference between the present comparative example and Example 3 is that the present comparative example uses an equal amount of nano aluminum hydroxide instead of nano flame retardant.

[0047] Comparative Example 7 The preparation method of the flame-retardant heat-resistant conveyor belt in the present comparative example is similar to that of Example 3, and the difference between the present comparative example and Example 3 is that the accelerator in the present comparative example is 2-mercaptobenzothiazole.

[0048] Test Example Heat resistance: The conveyor belts prepared in Examples 1-3 and Comparative Examples 1-7 were tested for heat resistance according to GB / T 33510-2017.

[0049] Oxygen index test: The test was performed using an HC-2 type oxygen index instrument produced by Nanjing Jiangning Analysis Instrument Factory. The conveyor belts prepared in Examples 1-3 and Comparative Examples 1-7 were tested according to GB / T 10707-2008, 15 samples of (80.0x6.5) mm were cut from each group of conveyor belts, and the average value of the oxygen index of the 15 samples in each group was recorded.

[0050] Vertical burning test: The conveyor belts prepared in Examples 1-3 and Comparative Examples 1-7 were tested according to GB / T 10707-2008, 5 samples of (130.0x13) mm were cut from the conveyor belts, placed vertically, and the combustion phenomenon was recorded after applying flame twice from the bottom, and then graded.

[0051] Mechanical Properties: Mechanical properties of the conveyor belts prepared in Examples 1-3 and Comparative Examples 1-7 were tested using a UTM4203 universal electronic testing machine manufactured by Shenzhen Sansi Zongheng Technology Co., Ltd. Tensile strength and elongation at break were tested in accordance with GB / T 528-2009, with the strips cut into dumbbell shapes and a displacement of 500 mm / min. Tear strength was tested in accordance with GB / T 529-2008, with the strips cut into rectangular shapes and a displacement of 500 mm / min.

[0052] The test results are shown in Tables 1 and 2.

[0053] Table 1 Flame retardant and heat resistance test results

[0054] Table 2 Mechanical properties test results

[0055] As can be seen from Table 1, the burning depth of the flame retardant and heat-resistant conveyor belt provided by the present invention is less than 0.15 mm, the limiting oxygen index is 37.9%-39.5%, and the vertical burning grade is V-0, which fully demonstrates that the flame retardant and heat-resistant conveyor belt provided by the present invention has good flame retardant and heat-resistant properties; as can be seen from Table 2, the tensile strength of the flame retardant and heat-resistant conveyor belt provided by the present invention is 8.84-9.10 MPa, the elongation at break is 937%-956%, and the tear strength is 17.11-18.32 N / mm, which shows that the flame retardant and heat-resistant conveyor belt provided by the present invention has good mechanical properties.

[0056] Compared with Example 3, Comparative Example 1 uses an equal amount of nano flame retardant to replace the flame retardant resin, but the flame retardant performance of the obtained conveyor belt is reduced and the mechanical properties are increased. Comparative Example 2 uses an equal amount of flame retardant resin to replace the nano flame retardant, but the flame retardant performance and mechanical properties of the obtained conveyor belt are reduced to varying degrees, which shows that the flame retardant resin and the nano flame retardant in the present invention play a synergistic effect. The nano flame retardant can improve the flame retardant performance of the conveyor belt while also improving the mechanical properties of the conveyor belt; Comparative Example 3 uses an equal amount of phenyltriethoxysilane to replace phenyl dichlorophosphate, and the flame retardant performance of the obtained conveyor belt deteriorates, which is due to the fact that no phosphate group is introduced into the flame retardant resin; Comparative Example 4 changes the molar ratio of phenyltriethoxysilane, p-methylphenyltriethoxysilane and phenyl dichlorophosphate, but the flame retardant performance of the obtained conveyor belt deteriorates, which shows that the flame retardant resin In the preparation process, the molar ratio of phenyltriethoxysilane, p-methylphenyltriethoxysilane and phenyl dichlorophosphate has been optimized; in comparative example 5, an equal amount of vinyltrimethoxysilane is used instead of bisphenol A-bis(diphenyl phosphate), but the flame retardant properties of the obtained conveyor belt are deteriorated; in comparative example 6, an equal amount of nano-aluminum hydroxide is used instead of the nano-flame retardant, but the flame retardant properties and mechanical properties of the obtained conveyor belt are both deteriorated, which shows that the introduction of phosphate groups on the surface of nano-aluminum hydroxide in the present invention can effectively improve the flame retardant properties of the conveyor belt, and at the same time, the modification of nano-aluminum hydroxide can improve its compatibility with the covering rubber; in comparative example 7, the type of accelerator is changed, but the mechanical properties of the obtained conveyor belt are deteriorated, which shows that the use of 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfonamide to form an accelerator in the present invention can effectively improve the mechanical properties of the conveyor belt.

[0057] In addition, the present invention also conducted infrared spectrum test on the flame retardant resin prepared in Preparation Example 3, and the test results are shown in FIG. Figure 1 .Depend on Figure 1 It can be seen that at 1025m -1 The stretching vibration peak of Si-O-Si appears at 1127 cm -1 The absorption peak of Si-phenyl appeared at 3082 cm -1 1589cm -1 1430cm -1 The absorption peak of phenyl group appeared at 2953cm -1 The absorption peak of benzyl appeared at 1318 cm -1 The absorption peak of -P=O appeared at 1062cm -1 The absorption peak of COP appears at , which indicates that the present invention successfully introduces phosphate groups into the silicone resin structure.

[0058] The above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Persons skilled in the art should not modify the above embodiments without departing from the spirit and scope of the present invention. Any equivalent modifications or alterations made by persons skilled in the art without departing from the technical spirit of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A flame retardant and heat resistant conveyor belt, characterized in that: It includes a skeleton layer and a covering rubber layer, and the covering rubber layer includes the following components and their weight proportions: 50-70 parts of EPDM rubber, 40-50 parts of nitrile rubber, 30-40 parts of flame retardant resin, 10-15 parts of reinforcing agent, 10-20 parts of nano flame retardant, 3-8 parts of accelerator, 5-10 parts of antioxidant, and 5-10 parts of sulfur; The flame retardant resin is prepared by adding phenyltriethoxysilane, p-methylphenyltriethoxysilane and ethanol into a reaction kettle, adding phenyl dichlorophosphate, stirring evenly, heating to 70-80° C. and reacting for 1.5-2 hours, continuously heating to 95-100° C. and reacting for 1.6-2.2 hours, continuously heating to 105-110° C. and reacting for 0.5-1 hour, then performing reduced pressure distillation, and cooling to obtain the flame retardant resin.

2. The flame retardant and heat resistant conveyor belt according to claim 1, characterized in that: In the preparation method of the flame retardant resin, the molar ratio of phenyltriethoxysilane, p-methylphenyltriethoxysilane and phenyl dichlorophosphate is 3-5:1:2-3.

3. The flame retardant and heat resistant conveyor belt according to claim 1, characterized in that: The temperature of the reduced pressure distillation in the preparation method of the flame retardant resin is carried out in stages, namely 100-105°C, 110-115°C, 120-130°C, 140-145°C, and 150-155°C, and the time of the reduced pressure distillation is 30-40min, 25-30min, 25-30min, 25-30min, and 80-90min, respectively.

4. The flame retardant and heat resistant conveyor belt according to claim 1, characterized in that: The preparation method of the nano flame retardant comprises the following steps: adding nano aluminum hydroxide to acetone, performing ultrasonic dispersion, heating to 65-70° C., adding bisphenol A-bis(diphenyl phosphate) dropwise, stirring for 3-4 hours, cooling, performing vacuum distillation, drying, and grinding to obtain the nano flame retardant.

5. The flame retardant and heat resistant conveyor belt according to claim 4, characterized in that: In the preparation method of the nano flame retardant, the molar ratio of the nano aluminum hydroxide to bisphenol A-bis(diphenyl phosphate) is 3-5:1-2.

6. The flame retardant and heat resistant conveyor belt according to claim 5, characterized in that: In the preparation method of the nano flame retardant, the power of the ultrasonic dispersion is 30-40 kHz, the duty cycle is 30%-40%, and the ultrasonic dispersion time is 2-4 hours; the temperature of the vacuum distillation is 60-70° C., and the vacuum distillation time is 40-50 minutes.

7. The flame retardant and heat resistant conveyor belt according to claim 1, characterized in that: The accelerator is composed of 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazole sulfenamide in a mass ratio of 8-12:5-7.

8. The flame retardant and heat resistant conveyor belt according to claim 1, characterized in that: The reinforcing agent is one or more of carbon black, white carbon black, calcium carbonate, kaolin, and talc; the antioxidant is one or more of antioxidant 4020, antioxidant 4010NA, microcrystalline wax, antioxidant 168, and antioxidant 1010; and the skeleton layer is aramid canvas.

9. The method for preparing a flame retardant and heat resistant conveyor belt according to any one of claims 1 to 8, characterized in that: Specifically: S1: EPDM rubber, NBR and flame retardant resin are mixed in an internal mixer, and then reinforcing agent, nano flame retardant, accelerator, antioxidant and sulfur are added and mixed to obtain a covering rubber; S2: Impregnating the skeleton layer material in liquid phenolic resin, then heating to 60-80°C, keeping warm for 5-10 minutes, and continuing to heat to 140-160°C, keeping warm for 10-15 minutes to obtain an impregnated skeleton; S3: Compounding the covering rubber obtained in step S1 with the impregnated skeleton obtained in step S2, and then performing a vulcanization treatment to obtain a flame-retardant and heat-resistant conveyor belt.

10. The method for preparing a flame retardant and heat resistant conveyor belt according to claim 9, characterized in that: The blending temperature in step S1 is 140-160°C, and the blending time is 30-50 minutes; the kneading temperature is 140-160°C, and the kneading time is 20-40 minutes; the impregnation temperature in step S2 is 40-50°C, and the impregnation time is 0.5-1 minute; the vulcanization temperature in step S3 is 150-170°C.

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