A wear-resistant material for butterfly valve disc, preparation method and application thereof

Abstract

The present invention discloses a wear-resistant material, preparation method and application for butterfly valve disc, belonging to the technical field of butterfly valves. The wear-resistant material comprises a base product made by conventional one-piece injection molding process, and a wear-resistant sealing layer formed on the surface of the base product by ethylene-tetrafluoroethylene copolymer. The wear-resistant sealing layer formed by injection molding ethylene-tetrafluoroethylene copolymer on the surface of the base of the present invention has good corrosion resistance and wear resistance, improves the comprehensive performance of the product and prolongs the service life, and can meet the use requirements of the valve disc in different environments.

Description

Technical Field

[0001] The present invention relates to the technical field of butterfly valves, and in particular to a wear-resistant material for butterfly valve discs, a preparation method and an application thereof. Background Art

[0002] A butterfly valve, also called a flap valve, is a simple regulating valve that can be used for on-off control of low-pressure pipeline media. A butterfly valve is a valve whose closing member is a disc that rotates around the valve axis to achieve opening and closing.

[0003] Chinese patent CN109237084A discloses a double-flap check butterfly valve, the two ends of the valve body pipeline are respectively the inlet and outlet of the fluid, the middle pipe section of the valve body pipeline is provided with a waist-shaped valve port, the two sides of the waist-shaped valve port are respectively provided with left and right check valve flap assemblies of the same structure, and the left and right check valve flap assemblies cooperate to form a valve core opening and closing butterfly valve; vertical horizontal plates are arranged at the upper and lower parts of the middle part of the waist-shaped valve port, the arc-shaped parts at both ends of the waist-shaped valve port of the valve body pipeline are provided with arc-shaped inner flanges, the connection between the arc-shaped inner flange and the lower horizontal plate is provided with a jack, and the connection between the arc-shaped inner flange and the horizontal plate is provided with a through hole; the check valve flap assembly includes a valve flap, a hand wheel, a chuck, a rotating shaft, a valve flap rotating shaft, a sealing bolt, and a fan-shaped limit block. The invention can seal and adjust the flow of the fluid in the pipeline, and most importantly, it also has a check function. The double-flap check butterfly valve is smaller in size, lighter in weight, and can be quickly started, closed and checked, and is particularly suitable for circulation pipelines with high pressure.

[0004] Chinese patent CN110173571A provides a low-flow loss butterfly valve disc structure, in which the upper and lower ends of the butterfly valve disc are provided with upper and lower shaft holes, and the upper shaft hole is provided at the upper end of the butterfly valve disc in the stepped structure, and the upper shaft hole is provided at the upper end of the butterfly valve disc, and the A cylinder, truncated cone, B cylinder, and spherical cone are connected from top to bottom and formed in one piece; the lower shaft hole is provided at the lower end of the butterfly valve disc in the stepped structure, and the A cylinder, truncated cone, B cylinder, and spherical cone are connected from bottom to top and formed in one piece. When the butterfly valve disc of the invention is fully opened, under the premise of ensuring the sealing performance, the ratio of the flow area to the diameter area of ​​the butterfly valve is increased to 63-66%, and the ratio of the flow area of ​​the butterfly valve disc of the invention to the diameter area of ​​the butterfly valve is increased by 5-10%; the fluid flow rate is increased by 5-10%, and the fluid flow loss is reduced by 2-5KPa.

[0005] The butterfly valve disc used in the prior art is usually made of polypropylene. In practical applications, polypropylene has poor corrosion resistance and wear resistance, and is prone to structural defects and failure under special application conditions. Summary of the invention

[0006] In view of the above-mentioned defects in the prior art, the problem to be solved by the present invention is to provide a wear-resistant material for a butterfly valve disc, a preparation method and an application thereof.

[0007] A method for preparing a wear-resistant material for a butterfly valve disc comprises the following steps:

[0008] S1, matrix molding: heating the thermoplastic polymer matrix to a molten state, and using a conventional one-piece injection molding process to form a matrix finished product of a desired shape for standby use;

[0009] S2. Wear-resistant sealing layer molding: injection molding ethylene-tetrafluoroethylene copolymer on the surface of the finished valve disc substrate, placing the finished substrate into a mold, and treating it at a temperature of 180-330°C for 10-20 minutes. After the ethylene-tetrafluoroethylene copolymer is melt-molded to form an injection layer, it is taken out and naturally cooled to form a wear-resistant sealing layer on the surface of the finished substrate, thereby obtaining a wear-resistant material for the valve disc on a butterfly valve.

[0010] Preferably, the polymer matrix is ​​polypropylene or heat-stable polypropylene.

[0011] Preferably, the wear-resistant sealing layer has a thickness of 0.1 to 0.5 mm.

[0012] Both polypropylene and ethylene-tetrafluoroethylene copolymer are thermoplastic polymer materials. After forming with polypropylene as the matrix material, ethylene-tetrafluoroethylene copolymer can be injection molded on the surface of the matrix by secondary injection molding, and then the wear-resistant sealing layer is obtained by hot melting, leveling and cooling molding. However, there is a large difference in the thermoplastic processing temperature of polypropylene and ethylene-tetrafluoroethylene copolymer. The processing temperature of ethylene-tetrafluoroethylene copolymer is completely melted at 180-330°C, and the thermal stability of the polypropylene matrix is ​​not as good as that of ethylene-tetrafluoroethylene copolymer. When the ambient temperature is higher than 260°C, polypropylene begins to turn yellow and degrade. Therefore, in the preparation process of the wear-resistant sealing layer, the polypropylene matrix may be difficult to withstand the processing conditions of ethylene-tetrafluoroethylene copolymer, resulting in deformation or decomposition to produce partial defects, which in turn affects the comprehensive performance and service life of the finished wear-resistant material.

[0013] The existing technology can use the method of adding stabilizers or fillers to alleviate the process of matrix defect generation, but the above method cannot improve the inherent thermal stability of polypropylene. Stabilizers or fillers mainly alleviate degradation by deactivating the free radicals generated by the homolysis of hydroperoxides in the early stage of thermal degradation. However, when the stabilizing components are exhausted, defects will still appear in polypropylene. In addition, the compatibility of stabilizers or fillers with polypropylene needs to be improved, and it is difficult to prevent them from migrating to the surface and being lost, which leads to a decrease in stability.

[0014] The nitrogen atom positioning atom of 2-methylpyrrole absorbs electrons through the inductive effect, and the conjugated effect of the methyl group donates electrons, thereby enhancing the electron cloud density and having high reactivity. The present invention obtains pre-reaction monomer I and pre-reaction monomer II with different olefin chain lengths by substitution reaction of 2-methylpyrrole with 7-bromo-1-heptene and 9-bromo-1-nonene respectively; the pre-reaction monomer I and the pre-reaction monomer II are mixed in a specific ratio and form a ternary mixture with propylene, and are connected by polymerization reaction between carbon-carbon double bonds to obtain heat-stable polypropylene.

[0015] In heat-stable polypropylene, the interval between the carbon-nitrogen heterocycle of the side chain and the main chain is relatively long, which has no adverse effect on the electronic properties of the main chain. By introducing side chain segments with different chain lengths, the migration of the molecular chain at high temperature and the diffusion of free radicals are reduced. At the same time, the free radicals generated by high temperature inside the matrix material can react with the carbon-nitrogen heterocycle, and form coupled structures such as dimers through isomerization and carbon substitution, which can capture free radicals in the early stage of pyrolysis and prevent free radicals from destroying the main chain structure. The generated coupled structure forms new binding sites between molecular chains, so that the matrix can maintain good mechanical properties and thermal stability even at high temperatures.

[0016] Preferably, the preparation method of the heat-stable polypropylene is as follows:

[0017] M1, 2-methylpyrrole, potassium hydroxide and dimethyl sulfoxide are uniformly mixed, 7-bromo-1-heptene is added and a first substitution reaction is carried out; after the first substitution reaction is completed, the product is poured into excess deionized water, extracted with ethyl acetate, and the organic phase is collected, and the organic phase is dried and distilled under reduced pressure to obtain a pre-reaction monomer I for standby use;

[0018] M2, 2-methylpyrrole, potassium hydroxide and dimethyl sulfoxide are uniformly mixed, 9-bromo-1-nonene is added and a second substitution reaction is carried out; after the second substitution reaction is completed, the product is poured into excess deionized water, extracted with ethyl acetate, and the organic phase is collected, and the organic phase is dried and distilled under reduced pressure to obtain a pre-reaction monomer II for standby use;

[0019] M3. Mix pre-reaction monomer I and pre-reaction monomer II evenly to obtain reaction monomer; under closed and nitrogen protection, take the reaction monomer, catalyst and toluene and mix them evenly, pressurize propylene and carry out polymerization reaction; after the polymerization reaction, remove toluene by vacuum distillation, wash with anhydrous ethanol, and dry to obtain heat-stable polypropylene.

[0020] Specifically, the preparation method of the heat-stable polypropylene is as follows, in parts by weight:

[0021] M1, 2.20-2.85 parts of 2-methylpyrrole, 3.05-3.95 parts of potassium hydroxide and 15-20 parts of dimethyl sulfoxide are uniformly mixed, and 2.40-3.15 parts of 7-bromo-1-heptene are added to carry out a first substitution reaction; after the first substitution reaction is completed, the product is poured into an excess of deionized water at 0-4°C, extracted with ethyl acetate, and the organic phase is collected, and the organic phase is dried and distilled under reduced pressure to obtain a pre-reaction monomer I for standby use;

[0022] M2, 2.20-2.85 parts of 2-methylpyrrole, 3.05-3.95 parts of potassium hydroxide and 15-20 parts of dimethyl sulfoxide are uniformly mixed, and 2.80-3.65 parts of 9-bromo-1-nonene are added to carry out a second substitution reaction; after the second substitution reaction is completed, the product is poured into an excess of deionized water at 0-4°C, extracted with ethyl acetate, and the organic phase is collected, and the organic phase is dried and distilled under reduced pressure to obtain a pre-reaction monomer II for standby use;

[0023] M3. Pre-reaction monomer I and pre-reaction monomer II are mixed evenly to obtain reaction monomer; in a sealed and nitrogen-protected environment, 2.40 to 3.40 parts of the reaction monomer, 2.65 to 3.60 parts of bis(cyclopentadienyl)zirconium dichloride and 45 to 60 parts of toluene are mixed evenly, 17.50 to 29.50 parts of propylene are introduced under pressure to carry out polymerization reaction; after the polymerization reaction is completed, toluene is removed by vacuum distillation, and the mixture is washed with anhydrous ethanol and dried to obtain heat-stable polypropylene.

[0024] Preferably, the temperature of the first substitution reaction in step M1 is 55-70° C., and the reaction time is 8-16 hours.

[0025] Preferably, the temperature of the second substitution reaction in step M2 is 60-80° C., and the reaction time is 12-18 h.

[0026] In the reaction monomers of step M3, the mass ratio of pre-reaction monomer I to pre-reaction monomer II is 1:(1.40-2.40), preferably 1:1.85.

[0027] Preferably, the gas pressure of propylene in step M3 is 0.9-1.5 MPa.

[0028] Preferably, the polymerization reaction temperature in step M3 is 30-70° C., and the reaction time is 2-4 hours.

[0029] The present invention provides application of the wear-resistant material for the upper disc of a butterfly valve in preparing the upper disc of a butterfly valve.

[0030] A valve flap of a butterfly valve is made of a wear-resistant material used for valve flaps on butterfly valves. The valve flap includes a base 2, a wear-resistant sealing layer 3 and an annular convex portion 4. The surface of the base 2 is covered by the wear-resistant sealing layer 3, and the annular convex portion 4 is arranged on the wear-resistant sealing layer 3; the base 2 is made of a thermoplastic polymer base through an integral injection molding process, and the wear-resistant sealing layer 3 is made of ethylene-tetrafluoroethylene copolymer.

[0031] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0032] The introduction and functions of some raw materials in the formula of the present invention are as follows:

[0033] Ethylene-tetrafluoroethylene copolymer: Ethylene-tetrafluoroethylene copolymer (ETFE) is a chemical substance and is the toughest fluoroplastic. While maintaining the good heat resistance, chemical resistance and electrical insulation properties of PTFE, it has greatly improved radiation resistance and mechanical properties. The tensile strength can reach 50MPa, which is nearly twice that of polytetrafluoroethylene.

[0034] Beneficial effects of the present invention:

[0035] Compared with the prior art, the wear-resistant material used for the valve disc on the butterfly valve of the present invention includes a base product made by a conventional one-piece injection molding process, and a wear-resistant sealing layer formed on the surface of the base product with ethylene-tetrafluoroethylene copolymer; the wear-resistant sealing layer formed by injection-molding ethylene-tetrafluoroethylene copolymer on the surface of the base has good corrosion resistance and wear resistance, improves the comprehensive performance of the product and prolongs its service life, and can meet the use requirements of the valve disc in different environments.

[0036] Compared with the prior art, the present invention uses heat-stable polypropylene to prepare the matrix of the wear-resistant material. In the heat-stable polypropylene, the interval between the carbon-nitrogen heterocycle of the side chain and the main chain is relatively long, which has no adverse effect on the electronic properties of the main chain. By introducing side chain segments with different chain lengths, the migration of the molecular chain at high temperature and the diffusion of free radicals are reduced. At the same time, the free radicals generated inside the matrix material due to high temperature can react with the carbon-nitrogen heterocycle, and form coupled structures such as dimers through isomerization and carbon substitution, which play the function of capturing free radicals in the early stage of pyrolysis and prevent the free radicals from destroying the main chain structure. The generated coupled structure forms a new binding site between the molecular chains, so that the matrix can maintain good mechanical properties and thermal stability at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a cross-sectional view of the disc structure in a butterfly valve;

[0038] Figure numbers: 2 is the base, 3 is the sealing layer, and 4 is the wear-resistant annular convex part. DETAILED DESCRIPTION

[0039] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0040] Some raw material parameters in the comparative examples and embodiments of the present invention are as follows:

[0041] Ethylene-tetrafluoroethylene copolymer, brand: EC-6510, Daikin Industries, Ltd., Japan.

[0042] Example 1

[0043] A wear-resistant material for a butterfly valve disc is prepared by the following method:

[0044] S1. Matrix molding: After the heat-stable polypropylene is heated to 200°C and melted, the valve disc matrix product is made by an integrated injection molding process and is ready for use;

[0045] S2. Wear-resistant sealing layer molding: injection molding ethylene-tetrafluoroethylene copolymer on the surface of the finished valve disc substrate, placing the finished substrate into a mold, treating it at 330°C for 15 minutes, and taking it out after the ethylene-tetrafluoroethylene copolymer is melted and injection-molded to form an injection layer, and naturally cooling and molding to form a wear-resistant sealing layer on the surface of the finished substrate. The thickness of the wear-resistant sealing layer is 0.1mm, and a wear-resistant material for the valve disc on the butterfly valve is obtained.

[0046] The preparation method of the heat-stable polypropylene is as follows:

[0047] M1. 2.20 kg 2-methylpyrrole, 3.05 kg potassium hydroxide and 15 kg dimethyl sulfoxide were mixed evenly, 2.40 kg 7-bromo-1-heptene was added and the first substitution reaction was carried out. The temperature of the first substitution reaction was 60° C. and the reaction time was 12 h. After the first substitution reaction was completed, the product was poured into an excess of deionized water at 0° C., extracted with ethyl acetate, and the organic phase was collected. The organic phase was dried and distilled under reduced pressure to obtain pre-reaction monomer I for standby use.

[0048] M2, 2.20kg 2-methylpyrrole, 3.05kg potassium hydroxide and 15kg dimethyl sulfoxide were mixed evenly, 2.80kg 9-bromo-1-nonene was added and a second substitution reaction was carried out, the temperature of the second substitution reaction was 70°C, and the reaction time was 15h; after the second substitution reaction was completed, the product was poured into excess 0°C deionized water, extracted with ethyl acetate, and the organic phase was collected. The organic phase was dried and distilled under reduced pressure to obtain pre-reaction monomer II for standby use;

[0049] M3. Mix pre-reaction monomer I and pre-reaction monomer II in a mass ratio of 1:1.85 to obtain a reaction monomer; in a sealed and nitrogen-protected environment, take another 2.85 kg of the reaction monomer, 2.65 kg of bis(cyclopentadienyl)zirconium dichloride and 45 kg of toluene and mix them evenly, introduce 22.75 kg of propylene under pressure and carry out polymerization reaction, the gas pressure of propylene is 1.2 MPa, the polymerization temperature is 40°C, and the reaction time is 3 hours; after the polymerization reaction is completed, remove the toluene by vacuum distillation, wash with anhydrous ethanol, and dry to obtain heat-stable polypropylene.

[0050] Example 2

[0051] This embodiment is basically the same as embodiment 1, except that the preparation method of the heat-stable polypropylene is different. In this embodiment, the preparation method of the heat-stable polypropylene is as follows:

[0052] M1. 2.20 kg 2-methylpyrrole, 3.05 kg potassium hydroxide and 15 kg dimethyl sulfoxide were mixed evenly, 2.40 kg 7-bromo-1-heptene was added and the first substitution reaction was carried out. The temperature of the first substitution reaction was 60° C. and the reaction time was 12 h. After the first substitution reaction was completed, the product was poured into an excess of deionized water at 0° C., extracted with ethyl acetate, and the organic phase was collected. The organic phase was dried and distilled under reduced pressure to obtain pre-reaction monomer I for standby use.

[0053] M2, 2.20kg 2-methylpyrrole, 3.05kg potassium hydroxide and 15kg dimethyl sulfoxide were mixed evenly, 2.80kg 9-bromo-1-nonene was added and a second substitution reaction was carried out, the temperature of the second substitution reaction was 70°C, and the reaction time was 15h; after the second substitution reaction was completed, the product was poured into excess 0°C deionized water, extracted with ethyl acetate, and the organic phase was collected. The organic phase was dried and distilled under reduced pressure to obtain pre-reaction monomer II for standby use;

[0054] M3. Mix pre-reaction monomer I and pre-reaction monomer II in a mass ratio of 1:1.40 to obtain a reaction monomer; in a sealed and nitrogen-protected environment, take another 2.40 kg of the reaction monomer, 2.65 kg of bis(cyclopentadienyl)zirconium dichloride and 45 kg of toluene and mix them evenly, introduce 17.50 kg of propylene under pressure and carry out polymerization reaction, the gas pressure of propylene is 1.2 MPa, the polymerization temperature is 40°C, and the reaction time is 3 hours; after the polymerization reaction is completed, remove the toluene by vacuum distillation, wash with anhydrous ethanol, and dry to obtain heat-stable polypropylene.

[0055] Example 3

[0056] This embodiment is basically the same as embodiment 1, except that the preparation method of the heat-stable polypropylene is different. In this embodiment, the preparation method of the heat-stable polypropylene is as follows:

[0057] M1. 2.20 kg 2-methylpyrrole, 3.05 kg potassium hydroxide and 15 kg dimethyl sulfoxide were mixed evenly, 2.40 kg 7-bromo-1-heptene was added and the first substitution reaction was carried out. The temperature of the first substitution reaction was 60° C. and the reaction time was 12 h. After the first substitution reaction was completed, the product was poured into an excess of deionized water at 0° C., extracted with ethyl acetate, and the organic phase was collected. The organic phase was dried and distilled under reduced pressure to obtain pre-reaction monomer I for standby use.

[0058] M2, 2.20kg 2-methylpyrrole, 3.05kg potassium hydroxide and 15kg dimethyl sulfoxide were mixed evenly, 2.80kg 9-bromo-1-nonene was added and a second substitution reaction was carried out, the temperature of the second substitution reaction was 70°C, and the reaction time was 15h; after the second substitution reaction was completed, the product was poured into excess 0°C deionized water, extracted with ethyl acetate, and the organic phase was collected. The organic phase was dried and distilled under reduced pressure to obtain pre-reaction monomer II for standby use;

[0059] M3. Mix pre-reaction monomer I and pre-reaction monomer II in a mass ratio of 1:2.40 to obtain a reaction monomer; in a sealed and nitrogen-protected environment, take another 3.40 kg of the reaction monomer, 2.65 kg of bis(cyclopentadienyl)zirconium dichloride and 45 kg of toluene and mix them evenly, introduce 29.50 kg of propylene under pressure and carry out polymerization reaction, the gas pressure of propylene is 1.2 MPa, the polymerization temperature is 40°C, and the reaction time is 3 hours; after the polymerization reaction is completed, remove the toluene by vacuum distillation, wash with anhydrous ethanol, and dry to obtain heat-stable polypropylene.

[0060] Example 4

[0061] This embodiment is basically the same as embodiment 1, except that the preparation method of the heat-stable polypropylene is different. In this embodiment, the preparation method of the heat-stable polypropylene is as follows:

[0062] The preparation method of the heat-stable polypropylene is as follows:

[0063] M1. Evenly mix 2.20 kg 2-methylpyrrole, 3.05 kg potassium hydroxide and 15 kg dimethyl sulfoxide, add 2.40 kg 7-bromo-1-heptene and carry out substitution reaction. The temperature of substitution reaction is 60° C. and the reaction time is 12 h. After the substitution reaction is completed, pour the product into excess 0° C. deionized water, extract with ethyl acetate, collect the organic phase, dry the organic phase, and distill under reduced pressure to obtain a pre-reaction monomer for standby use.

[0064] M2. In a sealed and nitrogen-protected environment, 2.85 kg of the pre-reaction monomer, 2.65 kg of bis(cyclopentadienyl)zirconium dichloride and 45 kg of toluene were mixed evenly, and 22.75 kg of propylene was introduced under pressure to carry out polymerization reaction. The gas pressure of propylene was 1.2 MPa, the polymerization temperature was 40°C, and the reaction time was 3 h. After the polymerization reaction, toluene was removed by vacuum distillation, and the mixture was washed with anhydrous ethanol and dried to obtain heat-stable polypropylene.

[0065] Example 5

[0066] This embodiment is basically the same as embodiment 1, except that the preparation method of the heat-stable polypropylene is different. In this embodiment, the preparation method of the heat-stable polypropylene is as follows:

[0067] M1. 2.20 kg 2-methylpyrrole, 3.05 kg potassium hydroxide and 15 kg dimethyl sulfoxide were mixed evenly, and 2.80 kg 9-bromo-1-nonene was added to carry out a substitution reaction. The temperature of the substitution reaction was 70° C. and the reaction time was 15 h. After the substitution reaction was completed, the product was poured into an excess of 0° C. deionized water, extracted with ethyl acetate, and the organic phase was collected. The organic phase was dried and distilled under reduced pressure to obtain a pre-reaction monomer for standby use.

[0068] M2. In a sealed and nitrogen-protected environment, 2.85 kg of the pre-reaction monomer, 2.65 kg of bis(cyclopentadienyl)zirconium dichloride and 45 kg of toluene were mixed evenly, and 22.75 kg of propylene was introduced under pressure to carry out polymerization reaction. The gas pressure of propylene was 1.2 MPa, the polymerization temperature was 40°C, and the reaction time was 3 h. After the polymerization reaction, toluene was removed by vacuum distillation, and the mixture was washed with anhydrous ethanol and dried to obtain heat-stable polypropylene.

[0069] Comparative Example 1

[0070] A wear-resistant material for a butterfly valve disc is prepared by the following method:

[0071] S1. Matrix molding: After heating polypropylene to 200°C to melt, the valve disc matrix product is made by one-piece injection molding process for standby use;

[0072] S2. Wear-resistant sealing layer molding: injection molding ethylene-tetrafluoroethylene copolymer on the surface of the finished valve disc substrate, placing the finished substrate into a mold, treating it at 330°C for 15 minutes, and taking it out after the ethylene-tetrafluoroethylene copolymer is melted and injection-molded to form an injection layer, and naturally cooling and molding to form a wear-resistant sealing layer on the surface of the finished substrate. The thickness of the wear-resistant sealing layer is 0.1mm, and a wear-resistant material for the valve disc on the butterfly valve is obtained.

[0073] Test Example 1

[0074] The initial thermal decomposition temperature of the heat-stable polypropylene used in the wear-resistant material of the disc on the butterfly valve is measured by thermogravimetric analysis. The test is carried out according to the method and steps provided in the standard SN / T 3078.2-2015 "Determination of Thermal Stability of Chemicals Part 2: Thermogravimetric Analysis". The initial thermal decomposition temperature of the heat-stable polypropylene under air atmosphere is tested; the test group is the heat-stable polypropylene prepared in some embodiments, and the control group is the ordinary commercial polypropylene used in the control example. The sample mass is 5 mg, the heating rate during the test is 10℃ / min, and the test temperature range is from room temperature to 600℃. The test instrument is a HTG-4 thermogravimetric analyzer (Beijing Hengjiu Experimental Equipment Co., Ltd.), and the initial thermal decomposition temperature of the sample is measured and recorded by the software supporting the thermogravimetric analyzer. Each group is tested three times in parallel, and the results are taken as the arithmetic mean. The test results of the initial thermal decomposition temperature of the heat-stable polypropylene are shown in Table 1.

[0075] Table 1:

[0076]

[0077]

[0078] It can be seen from the test results in Table 1 that the initial thermal decomposition temperatures of Examples 1 and 5 are higher than the maximum processing temperature of ethylene-tetrafluoroethylene copolymer. Among them, the initial thermal decomposition temperature of Example 1 is the highest, which can well adapt to the molding conditions of the wear-resistant sealing layer. The initial thermal decomposition temperatures of Examples 4 and 5 are close to 330°C, and it is possible to consider appropriately lowering the processing temperature to prevent thermal degradation, but the leveling performance of some ethylene-tetrafluoroethylene copolymers will be sacrificed; commercial polypropylene cannot withstand a processing temperature of 300-330°C.

[0079] The reason for this result may be that in the heat-stable polypropylene, the interval between the carbon-nitrogen heterocycle of the side chain and the main chain is relatively long, which has no adverse effect on the electronic properties of the main chain. By introducing side chain segments with different chain lengths, the migration of the molecular chain at high temperature and the diffusion of free radicals are reduced. At the same time, the free radicals generated by high temperature inside the matrix material can react with the carbon-nitrogen heterocycle, and form coupled structures such as dimers through isomerization and carbon substitution, which play the role of capturing free radicals in the early stage of pyrolysis and prevent free radicals from destroying the main chain structure. The generated coupled structure forms new binding sites between molecular chains, so that the matrix can maintain good mechanical properties and thermal stability even at high temperatures.

[0080] Test Example 2

[0081] The adhesion between the wear-resistant sealing layer and the substrate in the wear-resistant material used for the disc of the butterfly valve is tested according to the methods and steps provided in the standard GB / T 9286-2021 "Scratch test for paints and varnishes". The cutting adopts a rigid blade cutter with a V-shaped blade, and its shape meets the requirements of the standard. The test is carried out at 23°C and 50% relative humidity; before the test, the sample is conditioned for 24 hours at 23°C and 50% relative humidity. The number of cutting paths in each direction of the grid pattern is 6, and the cutting spacing in each direction is 2mm. After the test, the test results are graded according to the following standards: 1) Grade: 0, the cutting edge is completely smooth, and there is no shedding in the grid; 2) Grade: 1, a small amount of coating falls off at the intersection of the cut, but the affected cross-cut area is not more than 5%; 3) Grade: 2, the coating falls off at the intersection of the cut and / or along the edge of the cut, and the affected cross-cut area is greater than 5%, but not more than 15%; 4) Grade: 3, the coating falls off partially or completely in large pieces at the uncut edge, and / or falls off partially or completely at different parts of the grid, and the affected cross-cut area is greater than 15%, but not more than 35%; 5) Grade: 4, the coating falls off in large pieces at the uncut edge, and / or some squares fall off partially or completely, and the affected cross-cut area is greater than 35%, but not more than 65%; 5) Grade: 4, the degree of shedding exceeds Grade 4. The test results of the adhesion between the wear-resistant sealing layer and the substrate are shown in Table 2.

[0082] Table 2:

[0083] name Test result classification Example 1 0 Example 4 1 Example 5 0 Comparative Example 1 3

[0084] It can be seen from the test results in Table 2 that in Example 1 and Example 5, the wear-resistant sealing layer and the substrate exhibit excellent adhesion performance, among which Example 1 has the best adhesion effect, and there is no shedding in the grid; the adhesion of Control Example 1 is the lowest. The reason for the above results may be that the substrate materials of Example 1 and Example 5 can better withstand the processing temperature during the thermal processing of the wear-resistant sealing layer, there are fewer defects at the joint, and the bonding between the substrate and the wear-resistant sealing layer is more firm. The initial thermal decomposition temperature of the substrate material of Example 4 and Control Example 1 is lower than the processing temperature, so there are surface defects formed by thermal decomposition, which reduces the bonding ability of the wear-resistant sealing layer with it; and the initial thermal decomposition temperature of Example 4 is higher than that of Control Example 1. Compared with commercial polypropylene, Example 4 produces fewer defects under the same processing conditions, so the adhesion is better than that of Control Example 1.

[0085] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a wear-resistant material for a butterfly valve disc, characterized in that: The steps include: S1, matrix molding: heating the thermoplastic polymer matrix to a molten state, and using a conventional one-piece injection molding process to form a matrix finished product of a desired shape for standby use; S2, forming a wear-resistant sealing layer: injection molding an ethylene-tetrafluoroethylene copolymer on the surface of the finished valve disc substrate, placing the finished substrate in a mold, treating it at a temperature of 180-330° C. for 10-20 minutes, and taking it out after the ethylene-tetrafluoroethylene copolymer is melted and injection-molded to form an injection layer, and naturally cooling and molding to form a wear-resistant sealing layer on the surface of the finished substrate, thereby obtaining a wear-resistant material for the upper valve disc of a butterfly valve; The thickness of the wear-resistant sealing layer is 0.1-0.5 mm; The polymer matrix is ​​heat-stable polypropylene; The preparation method of the heat-stable polypropylene is as follows, in parts by weight: M1, 2.20-2.85 parts of 2-methylpyrrole, 3.05-3.95 parts of potassium hydroxide and 15-20 parts of dimethyl sulfoxide are mixed uniformly, 2.40-3.15 parts of 7-bromo-1-heptene are added and a first substitution reaction is carried out; after the first substitution reaction is completed, the product is poured into an excess of deionized water at 0-4°C, extracted with ethyl acetate, and the organic phase is collected, and the organic phase is dried and distilled under reduced pressure to obtain a pre-reaction monomer I for standby use; the temperature of the first substitution reaction in step M1 is 55-70°C, and the reaction time is 8-16h; M2, 2.20-2.85 parts of 2-methylpyrrole, 3.05-3.95 parts of potassium hydroxide and 15-20 parts of dimethyl sulfoxide are mixed uniformly, 2.80-3.65 parts of 9-bromo-1-nonene are added and a second substitution reaction is carried out; after the second substitution reaction is completed, the product is poured into an excess of deionized water at 0-4°C, extracted with ethyl acetate, and the organic phase is collected, and the organic phase is dried and distilled under reduced pressure to obtain a pre-reaction monomer II for standby use; the temperature of the second substitution reaction in step M2 is 60-80°C, and the reaction time is 12-18h; M3, pre-reaction monomer I and pre-reaction monomer II are mixed evenly to obtain a reaction monomer; under closed and nitrogen protection, 2.40-3.40 parts of the reaction monomer, 2.65-3.60 parts of bis(cyclopentadienyl)zirconium dichloride and 45-60 parts of toluene are mixed evenly, 17.50-29.50 parts of propylene are introduced under pressure to carry out polymerization reaction; after the polymerization reaction, toluene is removed by vacuum distillation, washed with anhydrous ethanol, and dried to obtain heat-stable polypropylene; the temperature of the polymerization reaction in step M3 is 30-70°C, and the reaction time is 2-4h; In the reaction monomers, the mass ratio of the pre-reaction monomer I to the pre-reaction monomer II is 1:(1.40-2.40).

2. A wear-resistant material for a butterfly valve disc, characterized in that: The method is prepared according to claim 1.

3. A valve flap for a butterfly valve, the valve flap comprising a base (2), a wear-resistant sealing layer (3) and an annular convex portion (4), the surface of the base (2) being covered by the wear-resistant sealing layer (3), the annular convex portion (4) being arranged on the wear-resistant sealing layer (3), characterized in that: The valve disc is made of the wear-resistant material for butterfly valve discs as claimed in claim 2; the base (2) is made of a thermoplastic polymer base through an integral injection molding process, and the wear-resistant sealing layer (3) is made of ethylene-tetrafluoroethylene copolymer.

Images