A high-strength flame-retardant sealing strip and preparation method thereof

Abstract

The present invention relates to the technical field of sealing strips and discloses a high-strength flame-retardant sealing strip and a preparation method thereof. The preparation method of the sealing strip is as follows: EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, an antioxidant, a dispersant, a vulcanizing agent and an activator are mixed, the mixture is refining, and vulcanization molding is performed to obtain a high-strength flame-retardant sealing strip. A halogen-free flame retardant system is adopted, and ammonia-containing and phosphorus-containing flame retardants and inorganic fillers are introduced. The components act synergistically to have excellent flame retardant properties and heat resistance, while avoiding secondary hazards generated during the combustion process. The carbon black can form a network structure in the rubber, and the basalt fiber forms a reinforcing skeleton in the rubber. The prepared sealing strip has excellent mechanical properties, high strength and excellent overall performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sealing strips, in particular to a high-strength flame-retardant sealing strip and a preparation method thereof. Background Art

[0002] Sealing strips are products used to seal objects or spaces. Their primary function is to prevent the penetration of liquids, gases, dust, and other substances, thereby providing shock absorption, waterproofing, sound insulation, heat insulation, dustproofing, and securing. They are widely used in automotive manufacturing, construction, electronic equipment, and other fields. Sealing strips are made from a variety of materials, including rubber, silicone, polymer plastics, and metal. With the rapid development of my country's economy and the automotive industry, the requirements for the materials used in the manufacture of automotive parts are becoming increasingly stringent, and the safety performance of automotive sealing strips is also increasing. They require not only excellent sealing properties but also high strength, flame retardancy, and weather resistance. EPDM rubber has excellent elasticity and excellent resistance to ozone, heat, and aging. It is used in automotive door and window sealing strips, sealing rings, and coolant hoses. However, rubber materials are prone to combustion when exposed to fire or high temperatures, and the flame spreads rapidly, posing certain safety risks. Furthermore, their low strength makes them less able to withstand external pressure.

[0003] Chinese patent application CN110577706A discloses a halogen-free flame-retardant EPDM sealing strip and its preparation method. The sealing strip comprises EPDM, carbon black, a flame retardant, a softening plasticizer, an activator, and a vulcanizer. The sealing strip has good high-temperature aging resistance and flame retardancy, but the dispersion of the raw materials is poor and the strength is average. Chinese patent application CN111138725A discloses a high-strength, wear-resistant modified natural rubber and its preparation method. The strip comprises natural rubber, EPDM, butadiene rubber, a reinforcing agent, epoxy resin, a silane coupling agent, an accelerator, an antioxidant, an emulsifier, and a plasticizer. The rubber has excellent mechanical strength, wear resistance, and aging resistance, but poor flame retardancy.

[0004] Therefore, the development of a sealing strip with high strength and good flame retardant performance has broad market prospects and application value. Summary of the Invention

[0005] (1) Technical problems solved

[0006] In order to solve the above technical problems, the present invention provides a high-strength flame-retardant sealing strip and a preparation method thereof, which solves the problems of poor flame-retardant performance and general strength of the sealing strip.

[0007] (2) Technical solution

[0008] In order to achieve the above object, the present invention discloses a method for preparing a high-strength flame-retardant sealing strip, comprising the following steps:

[0009] S1. Ultrasonic dispersion of carbon black in an ethanol solution. After uniform dispersion, γ-glycidyloxypropyltriethoxysilane is added, the mixture is stirred and mixed, and the temperature is increased to react. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol, and dried at 60° C. for 12 h to obtain epoxy-modified carbon black.

[0010] S2. Add epoxy-modified carbon black to an organic solvent, disperse it evenly with ultrasound, then add diaminodiphenyl sulfone, stir and mix evenly, increase the temperature to react, and after the reaction is completed, rotary evaporate to obtain modified carbon black;

[0011] S3, activating the basalt fiber with acetone for 4 hours, obtaining activated basalt fiber after the treatment, adding the activated basalt fiber to an ethanol solution, and then adding γ-methacryloxypropyltrimethoxysilane, stirring and mixing, reacting, and filtering after the reaction, washing with anhydrous ethanol, and drying in a vacuum drying oven at 80° C. for 12 hours to obtain olefinated basalt fiber;

[0012] S4, uniformly mixing the ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride, and an initiator, melt-blending the mixture in a twin-screw extruder, extruding the mixture, and cooling the mixture to obtain a basalt fiber grafted ethylene-octene copolymer;

[0013] S5. Add EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant and dispersant into an internal mixer, mix at 115-120°C for 8-10 minutes, add vulcanizer and activator, mix for 10-15 minutes to obtain a mixture, and refining the mixture in an open mixer. After refining, cool the mixture, let it stand for 12 hours, and then transfer it to a flat vulcanizer for vulcanization molding. Discharge the material to obtain a high-strength flame-retardant sealing strip.

[0014] Preferably, the ethanol solution in S1 consists of anhydrous ethanol and deionized water in a mass ratio of 9:1.

[0015] Preferably, the mass ratio of carbon black, ethanol solution and γ-glycidyloxypropyltriethoxysilane in S1 is 100:1500-1800:15-25.

[0016] Preferably, the reaction temperature in S1 is 55-65° C., and the reaction time is 6-9 h.

[0017] Preferably, the organic solvent in S2 includes any one or more of N,N-dimethylformamide, toluene, and dimethyl sulfoxide.

[0018] Preferably, the mass ratio of the organic solvent, epoxy-modified carbon black, and diaminodiphenyl sulfone in S2 is 950-1200:100:68-95.

[0019] Preferably, the reaction temperature in S2 is 95-105° C., and the reaction time is 4-6 h.

[0020] Preferably, the mass ratio of the activated basalt fiber, the ethanol solution, and γ-methacryloxypropyltrimethoxysilane in S3 is 100:1800-2100:18-25.

[0021] Preferably, the ethanol solution in S3 consists of anhydrous ethanol and deionized water in a mass ratio of 1:1.

[0022] Preferably, the reaction temperature in S3 is 25-35° C., and the reaction time is 12-15 h.

[0023] Preferably, the mass ratio of the ethylene-octene copolymer, the olefinated basalt fiber, the 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, the maleic anhydride and the initiator in the S4 is 100:10-15:3-5:18-25:2-4.

[0024] Preferably, the temperature of the melt blending in S4 is 165-195° C., and the time of the melt blending is 8-12 minutes.

[0025] Preferably, the initiator in S4 is dicumyl peroxide.

[0026] Preferably, the mass ratio of EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant, dispersant, vulcanizing agent and activator in S5 is 100:6-10:2-4:1-1.5:0.3-0.5:2-3:1-2.

[0027] Preferably, the dispersant in S5 includes any one of polyvinyl pyrrolidone, polyacrylamide, and polyvinyl alcohol.

[0028] Preferably, the antioxidant in S5 includes any one of antioxidant 168, antioxidant 1010, and antioxidant 1076.

[0029] Preferably, the vulcanizing agent in S5 is di-tert-butyl peroxide isopropylbenzene.

[0030] Preferably, the activator in S5 is stearic acid.

[0031] Preferably, the temperature of the rolling mill in S5 is 120-140° C., the rolling time is 8-10 min, the temperature of the vulcanization molding in the flat vulcanizing agent is 155-185° C., and the vulcanization molding time is 10-15 min.

[0032] A high-strength flame-retardant sealing strip prepared by adopting the method for preparing the high-strength flame-retardant sealing strip.

[0033] (3) Beneficial technical effects

[0034] In the present invention, carbon black is modified using γ-glycidyloxypropyltriethoxysilane to introduce epoxy groups onto the carbon black surface, resulting in epoxy-modified carbon black. The amino groups on diaminodiphenyl sulfone react with the epoxy groups on the epoxy-modified carbon black to produce modified carbon black. A flame retardant, amino groups, imine groups, and hydroxyl groups are also introduced into the carbon black. Basalt fiber is modified using γ-methacryloxypropyltrimethoxysilane to introduce alkenyl groups onto the basalt fiber, resulting in alkenylated basalt fiber. The alkenylated basalt fiber, ethylene-octene copolymer, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, and maleic anhydride are melt-blended in a twin-screw extruder and in situ polymerized to produce basalt fiber grafted with ethylene-octene copolymer, which also incorporates a phosphorus-containing flame retardant. The EPDM rubber, basalt fiber grafted ethylene-octene copolymer and modified carbon black are mixed, mixed in an internal mixer under the action of an additive, mixed in an open mixer, and vulcanized and formed in a flat vulcanizer to obtain a high-strength flame-retardant sealing strip.

[0035] Compared with the prior art, the present invention has the following technical effects:

[0036] (1) The carbon black used in the present invention has a large specific surface area and excellent thermal stability, weather resistance and chemical stability. As a reinforcing filler, it can significantly improve the tensile strength, tear strength and wear resistance of EPDM rubber. Carbon black can form a network structure in the rubber and interact with the rubber molecular chains to enhance the mechanical properties of the rubber. Basalt fiber has excellent mechanical properties, chemical stability and thermal stability. It forms a reinforcing skeleton in the rubber and can bear part of the tensile stress, thereby enhancing the tensile strength and modulus of EPDM rubber and improving its heat resistance and dimensional stability. It can also improve the vulcanization characteristics of the rubber. The double bonds in the ethylene-octene copolymer and the EPDM rubber can undergo cross-linking reaction to form a tighter network structure. At the same time, the active groups such as amino and hydroxyl groups introduced on the modified carbon black can form hydrogen bonds with the carboxyl groups introduced on the basalt fiber grafted ethylene-octene copolymer, and the synergistic effect can further improve the processing performance and low-temperature toughness of the EPDM rubber and improve the aging resistance and hot air aging resistance of the sealing strip.

[0037] (2) The present invention modifies carbon black and basalt fiber, effectively avoiding agglomeration and enabling them to be evenly dispersed in the matrix to form a uniform mechanical network structure. The resulting sealing strip has high strength and excellent mechanical properties. Furthermore, the diaminodiphenyl sulfone and phosphorus-containing flame retardant introduced into the matrix are not easy to precipitate and can maintain long-term flame retardancy. During the combustion of the matrix, the phosphorus heterocycle and diaminodiphenyl sulfone contained therein will generate phosphoric acid-containing substances, which will promote the carbonization of the matrix and prevent the combustion reaction from proceeding. At the same time, the PO· free radicals generated during the combustion process can capture ·OH and H· free radicals in the flame, interrupt the combustion chain reaction, and reduce the heat released by the combustion. The introduced nitrogen and sulfur elements can form non-combustible gases, dilute the oxygen concentration in the combustion system, and further improve the flame retardant effect. The organic silicon introduced in the preparation of basalt fiber grafted ethylene-octene copolymer and modified carbon black can increase the density of the carbon layer. During the combustion process, carbon black will form a heat-insulating and oxygen-isolating carbon layer, blocking the transfer of heat and the entry of oxygen, thereby inhibiting the combustion process.

[0038] (3) The sealing strip prepared in the present invention uses EPDM rubber as its matrix and adopts a halogen-free flame retardant system. The synergistic effect of the various components provides excellent flame retardancy and heat resistance, while avoiding secondary hazards during combustion. Furthermore, the sealing strip has excellent mechanical properties, high strength, and excellent overall performance. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] A method for preparing a high-strength flame-retardant sealing strip comprises the following steps:

[0042] S1. Ultrasonic dispersion of carbon black in an ethanol solution, wherein the ethanol solution is composed of anhydrous ethanol and deionized water in a mass ratio of 9:1. After uniform dispersion, γ-glycidyloxypropyltriethoxysilane is added, and the mass ratio of the added carbon black, ethanol solution, and γ-glycidyloxypropyltriethoxysilane is 100:1500:15. The mixture is stirred and mixed, heated, and reacted at 55° C. for 9 hours. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol, and dried at 60° C. for 12 hours to obtain epoxy-modified carbon black;

[0043] S2. Add epoxy-modified carbon black to N,N-dimethylformamide, disperse uniformly by ultrasonication, then add diaminodiphenyl sulfone. The mass ratio of N,N-dimethylformamide, epoxy-modified carbon black and diaminodiphenyl sulfone is 950:100:68. Stir and mix uniformly. Heat and react at 95°C for 6h. After the reaction is completed, rotary evaporate to obtain modified carbon black.

[0044] S3. Activate the basalt fiber with acetone for 4 hours. After the activation, obtain activated basalt fiber. Add the activated basalt fiber to an ethanol solution composed of anhydrous ethanol and deionized water in a mass ratio of 1:1, and then add γ-methacryloxypropyltrimethoxysilane. The mass ratio of the activated basalt fiber, the ethanol solution, and the γ-methacryloxypropyltrimethoxysilane is 100:1800:18. Stir and mix, react at 25° C. for 15 hours. After the reaction is completed, filter, wash with anhydrous ethanol, and dry in a vacuum drying oven at 80° C. for 12 hours to obtain olefinated basalt fiber.

[0045] S4, uniformly mixing ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride, and initiator dicumyl peroxide in a mass ratio of 100:10:3:18:2, melt blending in a twin-screw extruder at a temperature of 165° C. for 12 min, extruding, and cooling to obtain basalt fiber grafted ethylene-octene copolymer;

[0046] S5. Add EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010 and dispersant polyvinyl pyrrolidone into an internal mixer, mix at 115°C for 10 minutes, add vulcanizer di-tert-butyl peroxyisopropylbenzene and activator stearic acid, wherein the mass ratio of the added EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010, dispersant polyvinyl pyrrolidone, vulcanizer and activator is 100:6:2:1:0.3:2:1, mix for 15 minutes to obtain a mixture, and refining the mixture in an open mill at a refining temperature of 120°C and a refining time of 10 minutes. After refining, cool and stand for 12 hours, and then transfer to a flat vulcanizer for vulcanization molding at a vulcanization molding temperature of 155°C and a vulcanization molding time of 15 minutes. Discharge the material to obtain a high-strength flame-retardant sealing strip.

[0047] Example 2

[0048] A method for preparing a high-strength flame-retardant sealing strip comprises the following steps:

[0049] S1. Ultrasonic dispersion of carbon black in an ethanol solution, wherein the ethanol solution is composed of anhydrous ethanol and deionized water in a mass ratio of 9:1. After uniform dispersion, γ-glycidyloxypropyltriethoxysilane is added, and the mass ratio of the added carbon black, ethanol solution, and γ-glycidyloxypropyltriethoxysilane is 100:1700:18. The mixture is stirred and mixed, heated, and reacted at 60°C for 8 hours. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol, and dried at 60°C for 12 hours to obtain epoxy-modified carbon black;

[0050] S2. Add epoxy-modified carbon black to N,N-dimethylformamide, disperse uniformly by ultrasonication, then add diaminodiphenyl sulfone. The mass ratio of N,N-dimethylformamide, epoxy-modified carbon black and diaminodiphenyl sulfone is 1100:100:85. Stir and mix uniformly. Heat and react at 100°C for 5h. After the reaction is completed, rotary evaporate to obtain modified carbon black.

[0051] S3. Activate the basalt fiber with acetone for 4 hours. After the activation, obtain activated basalt fiber. Add the activated basalt fiber to an ethanol solution composed of anhydrous ethanol and deionized water in a mass ratio of 1:1. Then add γ-methacryloxypropyltrimethoxysilane. The mass ratio of the activated basalt fiber, ethanol solution, and γ-methacryloxypropyltrimethoxysilane is 100:1950:21. Stir and mix. React at 30° C. for 14 hours. After the reaction is completed, filter, wash with anhydrous ethanol, and dry in a vacuum drying oven at 80° C. for 12 hours to obtain olefinated basalt fiber.

[0052] S4, uniformly mixing ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride and initiator dicumyl peroxide in a mass ratio of 100:12:3.5:20:2.5, melt blending in a twin-screw extruder at a temperature of 175° C. for 9 min, extruding, and cooling to obtain basalt fiber grafted ethylene-octene copolymer;

[0053] S5. Add EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010 and dispersant polyvinyl pyrrolidone into an internal mixer, mix at 118°C for 9 minutes, add vulcanizer di-tert-butyl peroxyisopropylbenzene and activator stearic acid, wherein the mass ratio of the added EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010, dispersant polyvinyl pyrrolidone, vulcanizer and activator is 100:8:2.5:1.2:0.4:2.5:1.5, mix for 12 minutes to obtain a mixture, and refining the mixture in an open mill at a refining temperature of 125°C and a refining time of 9 minutes. After refining, cool and stand for 12 hours, and then transfer to a flat vulcanizer for vulcanization molding at a vulcanization molding temperature of 165°C and a vulcanization molding time of 12 minutes. Discharge the material to obtain a high-strength flame-retardant sealing strip.

[0054] Example 3

[0055] A method for preparing a high-strength flame-retardant sealing strip comprises the following steps:

[0056] S1. Evenly mix ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride, and initiator dicumyl peroxide in a mass ratio of 100:14:4.5:24:3.5, melt blend them in a twin-screw extruder at a temperature of 185° C. for 11 min, extrude, and cool to obtain basalt fiber grafted ethylene-octene copolymer;

[0057] S2. Add ethylene propylene diene monomer rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010 and dispersant polyvinyl pyrrolidone into an internal mixer, mix at 118°C for 9 minutes, add vulcanizing agent di-tert-butyl peroxyisopropyl benzene and activator stearic acid, wherein the mass ratio of the added ethylene propylene diene monomer rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010, dispersant polyvinyl pyrrolidone, vulcanizing agent and activator is 100:8:2.5:1.2:0.4:2.5:1.5, mix for 12 minutes to obtain a mixture, and refine the mixture in an open mill at a refining temperature of 125°C and a refining time of 9 minutes. After refining, cool and stand for 12 hours, and then transfer to a flat vulcanizer for vulcanization molding. The vulcanization molding temperature is 165°C and the vulcanization molding time is 12 minutes. Discharge to obtain a high-strength flame-retardant sealing strip.

[0058] The preparation method of the modified carbon black and olefinic basalt fiber is the same as the preparation method of the modified carbon black and olefinic basalt fiber in Example 2.

[0059] Example 4

[0060] A method for preparing a high-strength flame-retardant sealing strip comprises the following steps:

[0061] S1. Add ethylene propylene diene monomer rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010 and dispersant polyvinyl pyrrolidone into an internal mixer, mix at 118°C for 9 minutes, add vulcanizing agent di-tert-butyl peroxyisopropylbenzene and activator stearic acid, wherein the mass ratio of the added ethylene propylene diene monomer rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010, dispersant polyvinyl pyrrolidone, vulcanizing agent and activator is 100:9:3.5:1.4:0.45:2.5:1.5, mix for 14 minutes to obtain a mixture, and refining the mixture in an open mill at a refining temperature of 135°C and a refining time of 9 minutes. After refining, cool and stand for 12 hours, and then transfer to a flat vulcanizer for vulcanization molding at a vulcanization molding temperature of 175°C and a vulcanization molding time of 14 minutes. Discharge to obtain a high-strength flame-retardant sealing strip.

[0062] The preparation method of the modified carbon black and basalt fiber grafted ethylene-octene copolymer is the same as the preparation method of the modified carbon black and basalt fiber grafted ethylene-octene copolymer in Example 3.

[0063] Example 5

[0064] A method for preparing a high-strength flame-retardant sealing strip comprises the following steps:

[0065] S1. Ultrasonic dispersion of carbon black in an ethanol solution, wherein the ethanol solution is composed of anhydrous ethanol and deionized water in a mass ratio of 9:1. After uniform dispersion, γ-glycidyloxypropyltriethoxysilane is added, and the mass ratio of the added carbon black, ethanol solution, and γ-glycidyloxypropyltriethoxysilane is 100:1800:25. The mixture is stirred and mixed, heated, and reacted at 65°C for 6 hours. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol, and dried at 60°C for 12 hours to obtain epoxy-modified carbon black;

[0066] S2. Add epoxy-modified carbon black to N,N-dimethylformamide, disperse uniformly by ultrasonication, then add diaminodiphenyl sulfone. The mass ratio of N,N-dimethylformamide, epoxy-modified carbon black and diaminodiphenyl sulfone is 1200:100:95. Stir and mix uniformly. Heat and react at 105°C for 4h. After the reaction is completed, rotary evaporate to obtain modified carbon black.

[0067] S3. Activate the basalt fiber with acetone for 4 hours. After the activation, obtain activated basalt fiber. Add the activated basalt fiber to an ethanol solution composed of anhydrous ethanol and deionized water in a mass ratio of 1:1, and then add γ-methacryloxypropyltrimethoxysilane. The mass ratio of the activated basalt fiber, the ethanol solution, and the γ-methacryloxypropyltrimethoxysilane is 100:2100:25. Stir and mix, react at 35° C. for 12 hours. After the reaction is completed, filter, wash with anhydrous ethanol, and dry in a vacuum drying oven at 80° C. for 12 hours to obtain olefinated basalt fiber.

[0068] S4, uniformly mixing an ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride, and an initiator dicumyl peroxide in a mass ratio of 100:15:5:25:4, melt-blending the mixture in a twin-screw extruder at a temperature of 195° C. for 8 min, extruding, and cooling to obtain a basalt fiber grafted ethylene-octene copolymer;

[0069] S5. Add EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010 and dispersant polyvinyl pyrrolidone into an internal mixer, mix at 120°C for 8 minutes, add vulcanizer di-tert-butyl peroxyisopropylbenzene and activator stearic acid, wherein the mass ratio of the added EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant 1010, dispersant polyvinyl pyrrolidone, vulcanizer and activator is 100:10:4:1.5:0.5:3:2, mix for 10 minutes to obtain a mixture, and refining the mixture in an open mill at a refining temperature of 140°C and a refining time of 8 minutes. After refining, cool and stand for 12 hours, and then transfer to a flat vulcanizer for vulcanization molding at a vulcanization molding temperature of 185°C and a vulcanization molding time of 10 minutes. Discharge the material to obtain a high-strength flame-retardant sealing strip.

[0070] Comparative Example 1

[0071] A method for preparing a flame retardant sealing strip comprises the following steps:

[0072] S1. Activate the basalt fiber with acetone for 4 hours. After the activation, obtain activated basalt fiber. Add the activated basalt fiber to an ethanol solution composed of anhydrous ethanol and deionized water in a mass ratio of 1:1. Then add γ-methacryloxypropyltrimethoxysilane. The mass ratio of the activated basalt fiber, ethanol solution, and γ-methacryloxypropyltrimethoxysilane is 100:1950:21. Stir and mix. React at 30°C for 14 hours. After the reaction, filter, wash with anhydrous ethanol, and dry in a vacuum drying oven at 80°C for 12 hours to obtain olefinated basalt fiber.

[0073] S2, mixing ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride and initiator dicumyl peroxide in a mass ratio of 100:14:4.5:24:3.5, melt blending in a twin-screw extruder at a temperature of 185° C. for 11 min, extruding, and cooling to obtain basalt fiber grafted ethylene-octene copolymer;

[0074] S3. Add EPDM rubber, basalt fiber grafted ethylene-octene copolymer, carbon black, antioxidant 1010 and dispersant polyvinyl pyrrolidone into an internal mixer, mix at 118°C for 9 minutes, add vulcanizing agent di-tert-butyl peroxyisopropylbenzene and activator stearic acid, wherein the mass ratio of the added EPDM rubber, basalt fiber grafted ethylene-octene copolymer, carbon black, antioxidant 1010, dispersant polyvinyl pyrrolidone, vulcanizing agent and activator is 100:9:3.5:1.4:0.45:2.5:1.5, mix for 14 minutes to obtain a mixture, and refine the mixture in an open mill at a refining temperature of 135°C and a refining time of 9 minutes. After refining, cool and stand for 12 hours, and then transfer to a flat vulcanizer for vulcanization molding at a vulcanization molding temperature of 175°C and a vulcanization molding time of 14 minutes. Discharge to obtain a flame retardant sealing strip.

[0075] Comparative Example 2

[0076] A method for preparing a flame retardant sealing strip comprises the following steps:

[0077] S1. Ultrasonic dispersion of carbon black in an ethanol solution, wherein the ethanol solution is composed of anhydrous ethanol and deionized water in a mass ratio of 9:1. After uniform dispersion, γ-glycidyloxypropyltriethoxysilane is added, and the mass ratio of the added carbon black, ethanol solution, and γ-glycidyloxypropyltriethoxysilane is 100:1700:18. The mixture is stirred and mixed, heated, and reacted at 60°C for 8 hours. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol, and dried at 60°C for 12 hours to obtain epoxy-modified carbon black;

[0078] S2. Add epoxy-modified carbon black to N,N-dimethylformamide, disperse uniformly by ultrasonication, then add diaminodiphenyl sulfone. The mass ratio of N,N-dimethylformamide, epoxy-modified carbon black and diaminodiphenyl sulfone is 1100:100:85. Stir and mix uniformly. Heat and react at 100°C for 5h. After the reaction is completed, rotary evaporate to obtain modified carbon black.

[0079] S3, uniformly mixing an ethylene-octene copolymer, basalt fiber, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, maleic anhydride, and an initiator dicumyl peroxide in a mass ratio of 100:14:4.5:24:3.5, melt blending in a twin-screw extruder at a temperature of 185° C. for 11 min, extruding, and cooling to obtain a modified ethylene-octene copolymer;

[0080] S4. Add EPDM rubber, modified ethylene-octene copolymer, modified carbon black, antioxidant 1010 and dispersant polyvinyl pyrrolidone into an internal mixer, mix at 118°C for 9 minutes, add vulcanizer di-tert-butyl peroxyisopropylbenzene and activator stearic acid, wherein the mass ratio of the added EPDM rubber, modified ethylene-octene copolymer, modified carbon black, antioxidant 1010, dispersant polyvinyl pyrrolidone, vulcanizer and activator is 100:9:3.5:1.4:0.45:2.5:1.5, mix for 14 minutes to obtain a mixture, and refine the mixture in an open mill at a refining temperature of 135°C and a refining time of 9 minutes. After refining, cool and stand for 12 hours, and then transfer to a flat vulcanizer for vulcanization molding at a vulcanization molding temperature of 175°C and a vulcanization molding time of 14 minutes. Discharge the material to obtain a flame retardant sealing strip.

[0081] The carbon black used in the examples and comparative examples of the present invention was purchased from Qingdao Degussa Chemical Co., Ltd., model N330; basalt fiber was purchased from Zhejiang Shijin Company, with a length of 6 mm and a diameter of 13 μm; EPDM rubber was purchased from PetroChina Jilin Chemical Engineering Co., Ltd., model 2070; ethylene-octene copolymer (POE) was purchased from Dow Chemical, USA, model 8149; other undisclosed reagents were commercially available.

[0082] The flame retardant sealing strips prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to corresponding tests. The test methods and test results are as follows:

[0083] (1) Flame retardant performance test: The flame retardant sealing strips prepared in Examples 1-5 and Comparative Examples 1-2 were cut into strips with a size of 100 mm × 100 mm × 3 mm and placed on a JF-5 fully automatic oxygen index instrument for a limiting oxygen index test. The samples were placed vertically, ignited, and their oxygen concentrations were measured. Each group was tested three times, and the average value was taken.

[0084] (2) Mechanical property test: The flame-retardant sealing strips prepared in Examples 1-5 and Comparative Examples 1-2 were used as samples and subjected to tensile property tests on a CTM8000 universal material testing machine. The test standard was in accordance with the test standard of GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". The test temperature was 25°C, the load was 1000N, the tensile rate was 500mm / min, the specimens were dumbbell-shaped, and each group was tested three times, and the average value was taken.

[0085] The test results are shown in Table 1:

[0086] Table 1

[0087]

[0088] According to the test results in Table 1, it can be seen that the limiting oxygen index of the samples corresponding to Examples 1-5 all reached the flame retardant level, with excellent flame retardant properties and high strength. Among them, the limiting oxygen index of the sample corresponding to Example 4 reached 36.9%, the tensile strength was 15.0 MPa, and the elongation at break was 481%. In Comparative Example 1, the carbon black was not modified and was directly added to the matrix. The dispersibility of the carbon black in the matrix deteriorated, and the compatibility with the raw materials was poor, which had a certain impact on the flame retardant properties and greatly reduced the mechanical properties. In Comparative Example 2, the basalt fiber was not modified, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added at the same time. The dispersibility of the basalt fiber and the phosphorus-containing flame retardant deteriorated, the overall performance of the sample decreased, the flame retardancy was greatly reduced, and the mechanical properties deteriorated.

[0089] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and that all equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a high-strength flame-retardant sealing strip, characterized in that: The steps include: S1. Ultrasonic dispersion of carbon black in ethanol solution. After uniform dispersion, γ-glycidyloxypropyltriethoxysilane is added, the mixture is stirred and mixed, the temperature is increased, and a reaction occurs. After the reaction is completed, the mixture is filtered, washed, and dried at 60° C. for 12 h to obtain epoxy-modified carbon black. S2. Add epoxy-modified carbon black to an organic solvent, disperse it evenly with ultrasound, then add diaminodiphenyl sulfone, stir and mix evenly, increase the temperature to react, and after the reaction is completed, rotary evaporate to obtain modified carbon black; S3, activating the basalt fiber to obtain activated basalt fiber, adding the activated basalt fiber to an ethanol solution, and then adding γ-methacryloxypropyltrimethoxysilane, stirring and mixing to react. After the reaction is completed, filtering, washing, and vacuum drying at 60° C. for 12 hours to obtain olefinated basalt fiber; S4, uniformly mixing the ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride, and an initiator, melt-blending the mixture in a twin-screw extruder, extruding the mixture, and cooling the mixture to obtain a basalt fiber grafted ethylene-octene copolymer; S5. Add EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant and dispersant into an internal mixer and mix them. Then add vulcanizer and activator and mix them to obtain a mixture. The mixture is refining in an open mixer. After refining, it is cooled and then transferred to a flat vulcanizer for vulcanization molding. The material is discharged to obtain a high-strength flame-retardant sealing strip.

2. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: The mass ratio of carbon black, ethanol solution and γ-glycidyloxypropyltriethoxysilane in S1 is 100:1500-1800:15-25, the reaction temperature is 55-65° C., and the reaction time is 6-9 h.

3. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: The organic solvent in S2 includes any one or two of N,N-dimethylformamide, toluene, and dimethyl sulfoxide.

4. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: The mass ratio of the organic solvent, epoxy-modified carbon black, and diaminodiphenyl sulfone in S2 is 950-1200:100:68-95, the reaction temperature is 95-105° C., and the reaction time is 4-6 hours.

5. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: The mass ratio of the activated basalt fiber, ethanol solution and γ-methacryloxypropyltrimethoxysilane in S3 is 100:1800-2100:18-25, the reaction temperature is 25-35° C., and the reaction time is 12-15 hours.

6. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: The mass ratio of ethylene-octene copolymer, olefinated basalt fiber, 9,10-dihydro-9-oxa-10-allylphosphaphenanthrene-10-oxide, maleic anhydride, and initiator in S4 is 100:10-15:3-5:18-25:2-4, the melt blending temperature is 165-195° C., and the melt blending time is 8-12 min.

7. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: The initiator in S4 is dicumyl peroxide.

8. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: The mass ratio of EPDM rubber, basalt fiber grafted ethylene-octene copolymer, modified carbon black, antioxidant, dispersant, vulcanizer and activator in S5 is 100:6-10:2-4:1-1.5:0.3-0.5:2-3:1-2.

9. The method for preparing a high-strength flame-retardant sealing strip according to claim 1, characterized in that: In the S5, the temperature of the rolling mill is 120-140° C., the rolling time is 8-10 minutes, the temperature of the vulcanization molding in the flat vulcanizing agent is 155-185° C., and the vulcanization molding time is 10-15 minutes.

10. A high-strength flame-retardant sealing strip prepared by the method for preparing a high-strength flame-retardant sealing strip according to any one of claims 1 to 9.

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