Corrosion-resistant centrifugal water pump sealing filler and preparation method thereof

Abstract

The invention discloses a corrosion-resistant centrifugal water pump sealing filler and a preparation method thereof, and belongs to the technical field of sealing packings.The corrosion-resistant centrifugal water pump sealing filler comprises composite polyurethane powder and modified polytetrafluoroethylene powder, the composite polyurethane powder is obtained by compounding polyurethane and epoxy resin, and when polyurethane is prepared, the modified polytetrafluoroethylene powder is added into the composite polyurethane powder; cyanuric chloride with high chemical stability is introduced into 2-aminoethanolamine, so that a corrosion-resistant modified polyol solid is obtained, when epoxy resin is prepared, epoxy acrylate and tetrafluoroethylene are subjected to an addition polymerization reaction, so that a fluorine-carbon bond is introduced to the epoxy resin, the corrosion resistance of the epoxy resin is improved, and the corrosion resistance of the epoxy resin is improved. And the activated inorganic powder, nitrile rubber particles and polytetrafluoroethylene are subjected to ultraviolet radiation to obtain modified polytetrafluoroethylene, so that the mechanical property and wear resistance of the polytetrafluoroethylene are improved.

Description

Technical Field

[0001] The invention relates to the technical field of sealing fillers, and in particular to a corrosion-resistant centrifugal water pump sealing filler and a preparation method thereof. Background Art

[0002] Packing seal is a contact sealing method, that is, filling elastic sealing material between the shaft and the housing, using the elastic deformation of the sealing material to compensate for the wear of the cover, isolating the sealed space from the outside world, plugging the leakage gap and preventing the leakage of the medium. For key components of equipment such as the rotating shaft of a centrifugal water pump, the sealing packing needs to have sufficient corrosion resistance and chemical stability, and not be corroded or swelled by the medium. In addition, friction and wear performance is also one of the important properties that characterize the sealing characteristics of the material. Especially for dynamic seals, a high wear-resistant sealing material with a low friction coefficient will greatly extend the stability and life of the seal.

[0003] Polytetrafluoroethylene is a thermoplastic with high chemical stability, excellent lubricity and good thermal stability. It is widely used in the field of sealing materials. However, polytetrafluoroethylene has technical problems such as poor comprehensive mechanical properties and poor wear resistance. Polyurethane as a sealing material often has brittle cracking, which leads to water penetration at the joints. Therefore, it is necessary to toughen polyurethane to improve its deformation ability. Although nitrile rubber as an organic material has good oil resistance and physical and mechanical properties, organic materials have poor corrosion resistance. As a water sealing material, it is easy to have microscopic and macroscopic roughening after corrosion, thereby reducing its own wear resistance and mechanical properties. In addition, common centrifugal water pump sealing fillers also include carbon fiber and graphite powder, and how to modify the sealing materials in the prior art to obtain a sealing material composition having excellent corrosion resistance, wear resistance and comprehensive mechanical properties is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The object of the present invention is to provide a corrosion-resistant centrifugal water pump sealing filler and a preparation method thereof, so as to solve the technical defects proposed by the background technology.

[0005] The object of the present invention can be achieved by the following technical scheme: A corrosion-resistant centrifugal water pump sealing filler, which comprises 20-30 parts of composite polyurethane powder and 70 parts of modified polytetrafluoroethylene powder in parts by mass; The composite polyurethane powder is prepared by the following steps: S1, cyanuric chloride, anhydrous sodium carbonate powder and acetone are uniformly mixed, reacted at 0-5°C for 30-60 minutes, and then 2-aminoethanolamine is added dropwise to obtain a reaction mixture; the reaction mixture is first reacted at 10-20°C for 1-2 hours, then heated to 50-60°C for 1-2 hours, and then heated to 70-75°C for 2-3 hours to obtain a product; the product is filtered, washed and dried to obtain a modified polyol solid; With acetone as solvent and anhydrous sodium carbonate as catalyst, cyanuric chloride and 2-aminoethanolamine undergo nucleophilic substitution reaction to prepare a modified polyol solid.

[0006] The reaction formula for preparing modified polyol solids from cyanuric chloride and 2-aminoethanolamine is as follows:

[0007] S2, vacuum drying the modified polyol solid to obtain a dried modified polyol solid; mixing dibutyltin dilaurate, the modified polyol solid and the modified epoxy resin to obtain a mixture; dropping isophorone diisocyanate and diethanolamine into the mixture, reacting at 40-50° C. for 1.5-2 hours to obtain a prepolymer emulsion; adding acetic acid to the prepolymer emulsion to react for 30 minutes, then cooling to 10-20° C., adding deionized water, and emulsifying at 1000-2000 r / min for 30 minutes to obtain an aqueous polyurethane emulsion; S3. Pour the aqueous polyurethane emulsion into a polytetrafluoroethylene dish and dry it under vacuum to obtain a composite polyurethane.

[0008] Using dibutyltin dilaurate as a catalyst and diethanolamine as a chain extender, the hydroxyl group in the modified polyol, the hydroxyl group in the diethanolamine and the isocyanate group of isophorone diisocyanate are reacted to prepare a prepolymer emulsion terminated with -NCO; then acetic acid is used as a neutralizer, and deionized water is added for high-speed emulsification to obtain an aqueous polyurethane emulsion, and the aqueous polyurethane emulsion is vacuum dried to obtain a film, namely a polyurethane film, and in the process of synthesizing the aqueous polyurethane emulsion, a certain amount of modified epoxy resin is added to prepare a composite polyurethane.

[0009] Furthermore, in step S1, the usage ratio of cyanuric chloride, anhydrous sodium carbonate powder, acetone and 2-aminoethanolamine is 18g:1-3g:200mL:20-30g.

[0010] Further, in step S2, the modified epoxy resin is prepared by the following steps: Potassium persulfate, sodium bisulfite and deionized water are mixed evenly to obtain an initiator solution; epoxy acrylate and butanone are added into a three-necked flask and mixed and stirred, and then tetrafluoroethylene gas is introduced to fill the three-necked flask with tetrafluoroethylene gas, and then the three-necked flask is reacted at 70-75° C. for 8-10 hours, and the above initiator solution is added dropwise during the reaction. After the reaction is completed, the flask is naturally cooled to room temperature and filtered to obtain a solid; the solid is washed with anhydrous ethanol and vacuum dried to constant weight to obtain a modified epoxy resin.

[0011] A mixture of potassium persulfate and sodium bisulfite is used as an initiator, butanone is used as a solvent, and epoxy acrylate containing double bonds and tetrafluoroethylene are copolymerized to obtain a fluorine-containing modified epoxy resin.

[0012] Furthermore, the dosage ratio of potassium persulfate, sodium bisulfite and deionized water is 5g:1g:20mL; the dosage ratio of epoxy acrylate and butanone is 50g:200mL; and the temperature of vacuum drying is 50-60°C.

[0013] Furthermore, in step S2, the vacuum drying temperature of the modified polyol solid is 100-110°C, and the vacuum drying time is 1-2h; the amount ratio of dibutyltin dilaurate, the dried modified polyol solid and the modified epoxy resin is 3g:40-60g:10-20g; the amount ratio of isophorone diisocyanate, diethanolamine, acetic acid and deionized water is 20-30g:10g:3-5mL:100mL.

[0014] Furthermore, the preparation method of modified polytetrafluoroethylene powder comprises the following steps: A1. Grind fly ash microbeads to 10-20 μm to obtain ground fly ash microbeads; mix aluminum-titanium composite coupling agent and deionized water to obtain coupling agent solution; add the coupling agent solution dropwise to the ground fly ash microbeads, then heat to 100-200° C., mix and react for 5-10 minutes to obtain activated inorganic powder; Spherical fly ash microbeads are selected as inorganic fillers. The fly ash microbeads are ground to a certain particle size and then organically modified with an aluminum-titanium composite coupling agent to improve the compatibility of inorganic and organic materials. The fly ash microbeads modified with the coupling agent are activated at high temperature to improve their reaction activity, thereby preparing activated inorganic powder.

[0015] A2. Evenly mix the nitrile rubber particles, polytetrafluoroethylene and the activated inorganic powder to obtain a mixture; put the mixture into an irradiation device and irradiate it with gamma rays to obtain modified polytetrafluoroethylene.

[0016] The nitrile rubber particles, polytetrafluoroethylene and activated inorganic powder are mixed to obtain a mixture, and the mixture is irradiated with ultraviolet light to obtain modified polytetrafluoroethylene.

[0017] Furthermore, in step A1, the usage ratio of the aluminum-titanium composite coupling agent to deionized water is 5 g:100 mL; and the usage ratio of the coupling agent solution to the ground fly ash microbeads is 100 g:100-200 g.

[0018] Furthermore, in step A2, the usage ratio of nitrile rubber particles, polytetrafluoroethylene and activated inorganic powder is 10g:50g:10-20g; the irradiation temperature is 200°C, and the total irradiation dose is 20-300kGy.

[0019] The present invention also provides a method for preparing a corrosion-resistant centrifugal water pump sealing filler, comprising the following steps: B1. Grinding modified polytetrafluoroethylene into a powder of 300-500 mesh to obtain modified polytetrafluoroethylene powder; grinding composite polyester powder into a powder of 300-500 mesh to obtain composite polyester powder; mixing the composite polyester powder and modified polytetrafluoroethylene evenly to obtain sealing filler; B2. Maintain the sealing filler at a pressure of 50-100 MPa for 30 minutes to obtain a preform; and sinter the preform at a high temperature to obtain a corrosion-resistant centrifugal water pump sealing filler.

[0020] Furthermore, in step B2, the high temperature sintering temperature is 360-370°C, and the high temperature sintering pressure is 30-50MPa; during the sintering process, the sintering temperature is reached at a constant heating rate of 60°C, and then restored to room temperature at a constant heating rate of 30°C.

[0021] The present invention has the following beneficial effects: 1. The corrosion-resistant centrifugal water pump sealing filler prepared by the present invention comprises a composite polyurethane powder and a modified polytetrafluoroethylene powder. In the present invention, a certain amount of modified epoxy resin is added when synthesizing an aqueous polyurethane emulsion, thereby preparing a polyurethane / epoxy resin composite; the two polymer network structures of polyurethane and epoxy resin interpenetrate, entangle and cross-link each other, so that the two materials produce a synergistic effect, generate a composite polyurethane material with a mesh structure, and further improve its own toughness and thermal stability. In the preparation of polyurethane, the present invention modifies its component polyol; cyanuric chloride and 2-aminoethanolamine undergo nucleophilic substitution reaction, thereby obtaining a modified polyol solid. Since cyanuric chloride has strong chemical stability, it is not easy to decompose under high temperature, acid, alkali and light environment, thereby improving the corrosion resistance of the prepared modified polyol solid. Epoxy acrylate with unsaturated double bonds and tetrafluoroethylene undergo addition polymerization reaction, thereby introducing fluorine-carbon bonds on epoxy resin; fluorine-carbon bonds have extremely high bond energy and extremely small bond polarity, thereby improving the corrosion resistance of the modified epoxy resin, and then improving the corrosion resistance of the composite polyurethane powder.

[0022] 2. The present invention uses a mixture of activated inorganic powder, nitrile rubber particles and polytetrafluoroethylene for ultraviolet irradiation, thereby obtaining a modified polytetrafluoroethylene powder with high strength, corrosion resistance and friction resistance. Fly ash itself, as an inorganic powder, has the advantages of corrosion resistance, wear resistance and high strength; the present invention selects spherical fly ash and grinds it to micron level. The finer the particle size of the fly ash and the better the sphericity, the less adhesion between particles and the better the dispersion and fluidity of the fly ash, so that it is more suitable as a polymer filler. Since polytetrafluoroethylene itself has an extremely low friction coefficient and a very smooth surface, it is not conducive to compounding with inorganic powder; therefore, the present invention uses a coupling agent to modify the fly ash microbeads, thereby improving the compatibility of polytetrafluoroethylene and fly ash microbeads. After mixing nitrile rubber, activated inorganic powder and polytetrafluoroethylene, they are irradiated with ultraviolet light. Under certain ultraviolet irradiation temperature and ultraviolet irradiation time, the degree of crosslinking between polytetrafluoroethylene and nitrile rubber increases, thereby obtaining modified polytetrafluoroethylene with improved mechanical properties such as Shore hardness, tensile strength and elongation at break. The filling of organic materials with activated inorganic powder is beneficial to improving the wear resistance and corrosion resistance of modified polytetrafluoroethylene. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0024] This embodiment provides a method for preparing modified polytetrafluoroethylene powder for corrosion-resistant centrifugal water pump sealing filler, comprising the following steps: 1. Weigh 200g of fly ash microbeads, add the fly ash microbeads into a superfine grinder, grind to 10μm, and obtain ground fly ash microbeads; mix 5g of aluminum-titanium composite coupling agent HY-133 and 100mL of deionized water to obtain a coupling agent solution. Add the ground fly ash microbeads into a beaker, then drip the coupling agent solution into the beaker, transfer the beaker to an oil bath, heat to 100℃, mix and stir at 100r / min for 5min, and obtain activated inorganic powder.

[0025] 2. Mix 10 g of nitrile rubber particles, 50 g of polytetrafluoroethylene and 10 g of activated inorganic powder at 100 r / min for 10 min to obtain a mixture; put the mixture into an irradiation device, place it in an oxygen atmosphere, and irradiate it with gamma rays at 200° C. with a total irradiation dose of 20 kGy to obtain modified polytetrafluoroethylene. Example 2

[0026] This embodiment provides a method for preparing modified polytetrafluoroethylene powder for corrosion-resistant centrifugal water pump sealing filler, comprising the following steps: 1. Weigh 150g of fly ash microbeads, add the fly ash microbeads to the ultrafine grinding machine, grind to 15μm, and obtain the ground fly ash microbeads; mix 8g of aluminum-titanium composite coupling agent JTW-1618 and 100mL of deionized water to obtain a coupling agent solution. Add the ground fly ash microbeads to a beaker, and then drip the coupling agent solution into the beaker drop by drop. After the dripping is completed, transfer the beaker to an oil bath, heat to 110℃, and mix and stir at 100r / min for 6min to obtain activated inorganic powder.

[0027] 2. 10 g of nitrile rubber particles, 50 g of polytetrafluoroethylene and 15 g of activated inorganic powder are mixed evenly to obtain a mixture; the mixture is placed in an irradiation device, placed in an oxygen atmosphere, and irradiated with gamma rays at 260° C. with a total irradiation dose of 24 kGy to obtain modified polytetrafluoroethylene. Example 3

[0028] This embodiment provides a method for preparing modified polytetrafluoroethylene powder for corrosion-resistant centrifugal water pump sealing filler, comprising the following steps: 1. Weigh 100g of fly ash microbeads, add the fly ash microbeads into the ultrafine grinding machine, grind to 10-20μm, and obtain the ground fly ash microbeads; mix 10g of aluminum-titanium composite coupling agent HY-92 and 100mL of deionized water to obtain a coupling agent solution. Add the ground fly ash microbeads into a beaker, and then drip the coupling agent solution into the beaker drop by drop. After the dripping is completed, transfer the beaker to an oil bath, heat to 120℃, mix and stir at 100r / min for 10min to obtain activated inorganic powder.

[0029] 2. Evenly mix 10 g of nitrile rubber particles, 50 g of polytetrafluoroethylene and 20 g of activated inorganic powder to obtain a mixture; place the mixture in an irradiation device, place it in an oxygen atmosphere, and irradiate it with gamma rays at 300° C. with a total irradiation dose of 30 kGy to obtain modified polytetrafluoroethylene. Example 4

[0030] This embodiment provides a method for preparing a corrosion-resistant composite polyurethane for centrifugal water pump sealing filler, comprising the following steps: S1. Add 18g of cyanuric chloride, 1g of anhydrous sodium carbonate powder and 200mL of acetone to a 500mL three-necked flask, transfer the three-necked flask to an ice bath, and react at 0°C for 30min with mechanical stirring at 100r / min, then add 20g of 2-aminoethanolamine dropwise to the three-necked flask, and after the addition is complete, obtain a reaction mixture. Transfer the reaction mixture to a water bath, react at 10°C for 1h, then heat to 50°C for 1h, and then heat to 70°C for 2h to obtain a product; the product is filtered, washed, and dried to obtain a modified polyol solid.

[0031] S2. Mix 5g of potassium persulfate, 1g of sodium bisulfite and 20mL of deionized water to obtain an initiator solution; add 50g of epoxy acrylate and 200mL of butanone into a 500mL three-necked flask, and stir at 100r / min for 30min; connect one end of the three-necked flask to a dropping funnel, one end to a reflux device, and one end to an air duct, and introduce tetrafluoroethylene gas through the air duct to fill the three-necked flask with tetrafluoroethylene gas; then transfer the three-necked flask to a water bath, set the water bath temperature to 70°C, and react for 8h with mechanical stirring at 100r / min, adding all the initiator solution drop by drop during the reaction; after the reaction is completed, naturally cool to room temperature, filter, and obtain a solid; wash the solid three times with anhydrous ethanol, and vacuum dry it at 50°C to constant weight to obtain a modified epoxy resin.

[0032] S3. 40g of the modified polyol solid was vacuum dried at 100°C for 1h to obtain a dried modified polyol solid. A 500mL three-necked flask was filled with nitrogen. Under a nitrogen atmosphere, 3g of dibutyltin dilaurate, 40g of the dried modified polyol solid and 10g of modified epoxy resin were added in sequence, and mixed and stirred at 100r / min for 20min to obtain a mixture; the three-necked flask was transferred to a water bath, the temperature was adjusted to 40°C, and then 20g of isophorone diisocyanate and 10g of diethanolamine were added dropwise to the three-necked flask in sequence, and the mixture was reacted at this temperature for 1.5h to obtain a prepolymer emulsion.

[0033] 3 mL of acetic acid was added to the prepolymer emulsion for neutralization reaction for 30 minutes, then the temperature was lowered to 10°C, 100 mL of deionized water was added, and emulsification was carried out at a high speed of 1000 r / min for 30 minutes to obtain an aqueous polyurethane emulsion; the aqueous polyurethane emulsion was cast into a polytetrafluoroethylene dish, and then dried in a vacuum drying oven at 30°C for 24 hours to obtain a composite polyurethane. Example 5

[0034] This embodiment provides a method for preparing a corrosion-resistant composite polyurethane for centrifugal water pump sealing filler, comprising the following steps: S1. Add 18g of cyanuric chloride, 2g of anhydrous sodium carbonate powder and 200mL of acetone to a 500mL three-necked flask, transfer the three-necked flask to an ice bath, and react for 50min at 2°C with mechanical stirring at 100r / min, then add 25g of 2-aminoethanolamine dropwise to the three-necked flask, and after the addition is complete, obtain a reaction mixture. Transfer the reaction mixture to a water bath, react at 15°C for 1.3h, then heat to 55°C for 1.5h, and then heat to 72°C for 2.5h to obtain a product; the product is filtered, washed and dried to obtain a modified polyol solid.

[0035] S2. Evenly mix 5 g of potassium persulfate, 1 g of sodium bisulfite and 20 mL of deionized water to obtain an initiator solution; add 50 g of epoxy acrylate and 200 mL of butanone into a 500 mL three-necked flask, and stir at 100 r / min for 50 min; connect one end of the three-necked flask to a dropping funnel, one end to a reflux device, and one end to an air duct, and introduce tetrafluoroethylene gas through the air duct so that the three-necked flask is filled with tetrafluoroethylene gas; then transfer the three-necked flask to a water bath, set the water bath temperature to 72°C, and react for 9 hours with mechanical stirring at 100 r / min, adding all the initiator solution drop by drop during the reaction; after the reaction is completed, naturally cool to room temperature, filter, and obtain a solid; wash the solid three times with anhydrous ethanol, and vacuum dry it at 56°C to constant weight to obtain a modified epoxy resin.

[0036] S3, 50g of the modified polyol solid was vacuum dried at 105°C for 1.6h to obtain a dried modified polyol solid. A 500mL three-necked flask was filled with nitrogen. Under a nitrogen atmosphere, 3g of dibutyltin dilaurate, 50g of the dried modified polyol solid and 16g of modified epoxy resin were added in sequence, and mixed and stirred at 100r / min for 20min to obtain a mixture; the three-necked flask was transferred to a water bath, the temperature was adjusted to 45°C, and then 22g of isophorone diisocyanate and 10g of diethanolamine were added dropwise to the three-necked flask in sequence, and the mixture was reacted at this temperature for 1.8h to obtain a prepolymer emulsion.

[0037] 4 mL of acetic acid was added to the prepolymer emulsion for neutralization reaction for 30 min, then cooled to 15°C, 100 mL of deionized water was added, and emulsified at 1500 r / min for 30 min to obtain an aqueous polyurethane emulsion. The aqueous polyurethane emulsion was poured into a polytetrafluoroethylene dish, and then dried in a vacuum drying oven at 35°C for 24 h to obtain a composite polyurethane. Example 6

[0038] This embodiment provides a method for preparing a corrosion-resistant composite polyurethane for centrifugal water pump sealing filler, comprising the following steps: S1. Add 18g of cyanuric chloride, 3g of anhydrous sodium carbonate powder and 200mL of acetone to a 500mL three-necked flask, transfer the three-necked flask to an ice bath, and react for 60min at 5°C with mechanical stirring at 100r / min, then add 30g of 2-aminoethanolamine dropwise to the three-necked flask, and after the addition is complete, obtain a reaction mixture. Transfer the reaction mixture to a water bath, react at 20°C for 2h, then heat to 60°C for 2h, and then heat to 75°C for 3h to obtain a product; the product is filtered, washed and dried to obtain a modified polyol solid.

[0039] S2. Mix 5g of potassium persulfate, 1g of sodium bisulfite and 20mL of deionized water to obtain an initiator solution; add 50g of epoxy acrylate and 200mL of butanone into a 500mL three-necked flask, and stir at 100r / min for 60min; then connect one end of the three-necked flask to a dropping funnel, one end to a reflux device, and one end to an air duct, and introduce tetrafluoroethylene gas through the air duct to fill the three-necked flask with tetrafluoroethylene gas; then transfer the three-necked flask to a water bath, set the water bath temperature to 75°C, and react for 10h with mechanical stirring at 100r / min, adding all the initiator solution drop by drop during the reaction; after the reaction is completed, naturally cool to room temperature, filter, and obtain a solid; the solid is washed three times with anhydrous ethanol, and vacuum dried at 60°C to constant weight to obtain a modified epoxy resin.

[0040] S3, 60g of the modified polyol solid was vacuum dried at 110°C for 2h to obtain a dried modified polyol solid. A 500mL three-necked flask was filled with nitrogen, and 3g of dibutyltin dilaurate, 60g of the dried modified polyol solid and 20g of modified epoxy resin were added in sequence under a nitrogen atmosphere, and mixed and stirred at 100r / min for 20min to obtain a mixture; the three-necked flask was transferred to a water bath, and the temperature was adjusted to 50°C, and then 30g of isophorone diisocyanate and 10g of diethanolamine were added dropwise to the three-necked flask in sequence, and reacted at this temperature for 2h to obtain a prepolymer emulsion.

[0041] 5 mL of acetic acid was added to the prepolymer emulsion for neutralization reaction for 30 minutes, then cooled to 20°C, and 100 mL of deionized water was added, and emulsified at 2000 r / min for 30 minutes to obtain an aqueous polyurethane emulsion. The aqueous polyurethane emulsion was poured into a polytetrafluoroethylene dish and dried in a vacuum drying oven at 40°C for 24 hours to obtain a composite polyurethane. Example 7

[0042] This embodiment provides a method for preparing a corrosion-resistant centrifugal water pump sealing filler, comprising the following steps: S1. Grind the modified polytetrafluoroethylene into a powder of 300 mesh to obtain a modified polytetrafluoroethylene powder; grind the composite polyurethane into a powder of 300 mesh to obtain a composite polyurethane powder. Add 20g of the composite polyester powder and 70g of the modified polytetrafluoroethylene powder into a high-speed mixer, mix at 1000r / min for 5min, and then let stand for 10min; repeat the above operation twice until the modified polytetrafluoroethylene powder and the composite polyester powder are evenly mixed to obtain a sealing filler.

[0043] S2. Place the sealing filler in an environment of 25°C for 24 hours, then lay it flat in a mold and maintain the pressure at 50MPa for 30 minutes to obtain a preform. Transfer the preform to a high-temperature atmosphere furnace for sintering at a sintering temperature of 360°C and a sintering pressure of 30MPa. During the sintering process, the sintering temperature is reached at a constant heating rate of 60°C / h, and then it is restored to room temperature at a constant heating rate of 30°C / h to obtain a corrosion-resistant centrifugal water pump sealing filler. Example 8

[0044] This embodiment provides a method for preparing a corrosion-resistant centrifugal water pump sealing filler, comprising the following steps: S1. Grind the modified polytetrafluoroethylene into a powder of 400 mesh to obtain a modified polytetrafluoroethylene powder; grind the composite polyurethane into a powder of 400 mesh to obtain a composite polyurethane powder. Add 25g of the composite polyester powder and 70g of the modified polytetrafluoroethylene powder into a high-speed mixer, mix at 1000r / min for 5min, and then let stand for 10min; repeat the above operation twice until the modified polytetrafluoroethylene powder and the composite polyester powder are evenly mixed to obtain a sealing filler.

[0045] S2. Place the sealing filler in an environment of 25°C for 24 hours, then lay it flat in a mold and maintain the pressure at 80MPa for 30 minutes to obtain a preform. Transfer the preform to a high-temperature atmosphere furnace for sintering at a sintering temperature of 365°C and a sintering pressure of 40MPa. During the sintering process, the sintering temperature is reached at a constant heating rate of 60°C / h, and then it is restored to room temperature at a constant heating rate of 30°C / h to obtain a corrosion-resistant centrifugal water pump sealing filler. Example 9

[0046] This embodiment provides a method for preparing a corrosion-resistant centrifugal water pump sealing filler, comprising the following steps: S1. Grind the modified polytetrafluoroethylene into a powder of 500 mesh to obtain a modified polytetrafluoroethylene powder; grind the composite polyurethane into a powder of 500 mesh to obtain a composite polyurethane powder. Add 30g of the composite polyester powder and 70g of the modified polytetrafluoroethylene powder into a high-speed mixer, mix at 1000r / min for 5min, and then let stand for 10min; repeat the above operation twice until the modified polytetrafluoroethylene powder and the composite polyester powder are evenly mixed to obtain a sealing filler.

[0047] S2. Place the sealing filler in an environment of 25°C for 24 hours, then lay it flat in a mold and maintain the pressure at 100MPa for 30 minutes to obtain a preform. Transfer the preform to a high-temperature atmosphere furnace for sintering at a sintering temperature of 370°C and a sintering pressure of 50MPa. During the sintering process, the sintering temperature is reached at a constant heating rate of 60°C / h, and then it is restored to room temperature at a constant heating rate of 30°C / h to obtain a corrosion-resistant centrifugal water pump sealing filler.

[0048] Comparative Example 1 The difference between this comparative example and Example 9 is that no nitrile rubber is added when preparing the modified polytetrafluoroethylene.

[0049] Comparative Example 2 The difference between this comparative example and Example 9 is that when preparing the modified polytetrafluoroethylene, the fly ash microbeads are not modified by the aluminum-titanium composite coupling agent.

[0050] Comparative Example 3 The difference between this comparative example and Example 9 is that the epoxy acrylate is not modified when preparing the composite polyester.

[0051] Comparative Example 4 The difference between this comparative example and Example 9 is that when preparing the composite polyester, the 2-aminoethanolamine is not modified.

[0052] Performance Test: According to GB / T2918-1998 "Standard Environment for Conditioning and Experimentation of Plastic Samples", the Vickers hardness of the corrosion-resistant centrifugal water pump sealing packing prepared in Examples 7-9 and Comparative Examples 1-4 was tested by using the microscopic Vickers hardness test method. The arithmetic mean of the three test results was taken and compared with the Vickers hardness value table to find out the Vickers hardness value.

[0053] According to GB / T1040-2-2006 "Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics", the tensile strength and elongation at break of the corrosion-resistant centrifugal water pump sealing packings prepared in Examples 7-9 and Comparative Examples 1-4 were measured.

[0054] According to GB / T3960-1983 “Test Method for Sliding Wear and Friction of Plastics”, the wear amount of the corrosion-resistant centrifugal water pump sealing packings prepared in Examples 7-9 and Comparative Examples 1-4 was tested.

[0055] According to ASTMG32-16, the corrosion-resistant centrifugal water pump sealing fillers prepared in Examples 7-9 and the corrosion-resistant centrifugal water pump sealing fillers prepared in Comparative Examples 1-3 were tested for cavitation resistance: the sealing fillers were immersed in deionized water for 30 hours, and the cavitation cumulative mass loss value of the coating after immersion was recorded. Among them, the thickness of the sealing filler was 500 μm. The specific test results are shown in Table 1.

[0056] Table 1 - Performance test data of samples Category Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Vickers hardness / (Hv) 22.65 23.34 24.15 23.68 23.56 23.35 23.86 Elongation at break / (%) 421 433 456 401 452 455 448 Tensile strength / (MPa) 16.1 17.3 18.5 12.3 17.6 16.5 17.8 Wear amount / (mg) 0.8 0.7 0.6 0.7 0.6 0.4 0.4 Cavitation cumulative mass / (mg) 9 10 12 11 11 6 5 Data Analysis: Analyzing the data in Table 1, the corrosion-resistant centrifugal water pump sealing fillers prepared in Examples 7 to 9 of the present invention all have excellent mechanical properties, including high Vickers hardness values, elongation at break, and tensile strength values; The corrosion-resistant centrifugal water pump sealing packing prepared by the present invention has strong wear resistance and corrosion resistance, which is manifested in that the wear amount value and the cavitation cumulative mass value are small. In Comparative Example 1, since no nitrile rubber is added when preparing the modified polytetrafluoroethylene, the polytetrafluoroethylene is not cross-linked with the nitrile rubber, thereby reducing its own cross-linking degree, so that the mechanical properties of the modified polytetrafluoroethylene are significantly reduced, which is manifested in that the Vickers hardness, elongation at break and tensile strength values ​​are significantly reduced; In Comparative Example 3, when preparing the composite polyurethane, the epoxy acrylate was not modified by tetrafluoroethylene grafting; in Comparative Example 4, when preparing the composite polyurethane, the 2-aminoethanolamine was not modified by cyanuric chloride, both of which significantly reduced the corrosion resistance of the sealing filler, as manifested by a significant decrease in the value of the cumulative mass of cavitation.

[0057] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A corrosion-resistant centrifugal water pump sealing packing, characterized in that: Calculated by weight, it includes 20-30 parts of composite polyurethane powder and 70 parts of modified polytetrafluoroethylene powder; The composite polyurethane powder is prepared by the following steps: S1, cyanuric chloride, anhydrous sodium carbonate powder and acetone are uniformly mixed, reacted at 0-5°C for 30-60 minutes, and then 2-aminoethanolamine is added dropwise to obtain a reaction mixture; the reaction mixture is first reacted at 10-20°C for 1-2 hours, then heated to 50-60°C for 1-2 hours, and then heated to 70-75°C for 2-3 hours to obtain a product; the product is filtered, washed and dried to obtain a modified polyol solid; S2, vacuum drying the modified polyol solid to obtain a dried modified polyol solid; mixing dibutyltin dilaurate, the modified polyol solid and the modified epoxy resin to obtain a mixture; dropping isophorone diisocyanate and diethanolamine into the mixture, reacting at 40-50° C. for 1.5-2 hours to obtain a prepolymer emulsion; adding acetic acid to the prepolymer emulsion to react for 30 minutes, then cooling to 10-20° C., adding deionized water, and emulsifying at 1000-2000 r / min for 30 minutes to obtain an aqueous polyurethane emulsion; S3. Pour the aqueous polyurethane emulsion into a polytetrafluoroethylene dish and dry it under vacuum to obtain a composite polyurethane.

2. The corrosion-resistant centrifugal water pump sealing packing according to claim 1, characterized in that: In step S1, the usage ratio of cyanuric chloride, anhydrous sodium carbonate powder, acetone and 2-aminoethanolamine is 18g:1-3g:200mL:20-30g.

3. The corrosion-resistant centrifugal water pump sealing packing according to claim 1, characterized in that: In step S2, the modified epoxy resin is prepared by the following steps: Potassium persulfate, sodium bisulfite and deionized water are mixed evenly to obtain an initiator solution; epoxy acrylate and butanone are added into a three-necked flask and mixed and stirred, and then tetrafluoroethylene gas is introduced to fill the three-necked flask with tetrafluoroethylene gas, and then the three-necked flask is reacted at 70-75° C. for 8-10 hours, and the above initiator solution is added dropwise during the reaction. After the reaction is completed, the flask is naturally cooled to room temperature and filtered to obtain a solid; the solid is washed with anhydrous ethanol and vacuum dried to constant weight to obtain a modified epoxy resin.

4. The corrosion-resistant centrifugal water pump sealing packing according to claim 3, characterized in that: The dosage ratio of potassium persulfate, sodium bisulfite and deionized water is 5g:1g:20mL; the dosage ratio of epoxy acrylate and butanone is 50g:200mL; and the temperature of vacuum drying is 50-60°C.

5. The corrosion-resistant centrifugal water pump sealing packing according to claim 1, characterized in that: In step S2, the vacuum drying temperature of the modified polyol solid is 100-110° C., and the vacuum drying time is 1-2 h; the dosage ratio of dibutyltin dilaurate, the dried modified polyol solid and the modified epoxy resin is 3 g:40-60 g:10-20 g; the dosage ratio of isophorone diisocyanate, diethanolamine, acetic acid and deionized water is 20-30 g:10 g:3-5 mL:100 mL.

6. The corrosion-resistant centrifugal water pump sealing filler according to claim 1, characterized in that: The preparation method of modified polytetrafluoroethylene powder comprises the following steps: A1. Grind fly ash microbeads to 10-20 μm to obtain ground fly ash microbeads; mix aluminum-titanium composite coupling agent and deionized water to obtain coupling agent solution; add the coupling agent solution dropwise to the ground fly ash microbeads, then heat to 100-200° C., mix and react for 5-10 minutes to obtain activated inorganic powder; A2. Evenly mix the nitrile rubber particles, polytetrafluoroethylene and the activated inorganic powder to obtain a mixture; put the mixture into an irradiation device and irradiate it with gamma rays to obtain modified polytetrafluoroethylene.

7. The corrosion-resistant centrifugal water pump sealing filler according to claim 6, characterized in that: In step A1, the usage ratio of the aluminum-titanium composite coupling agent and deionized water is 5 g:100 mL; the usage ratio of the coupling agent solution and the ground fly ash microbeads is 100 g:100-200 g.

8. The corrosion-resistant centrifugal water pump sealing filler according to claim 6, characterized in that: In step A2, the usage ratio of nitrile rubber particles, polytetrafluoroethylene and activated inorganic powder is 10g:50g:10-20g; the irradiation temperature is 200°C, and the total irradiation dose is 20-30kGy.

9. A method for preparing the corrosion-resistant centrifugal water pump sealing filler according to any one of claims 1 to 8, characterized in that: The following steps are involved: B1. Grinding the modified polytetrafluoroethylene into a powder of 300-500 mesh to obtain modified polytetrafluoroethylene powder; Grinding the composite polyester powder into a powder of 300-500 mesh to obtain composite polyester powder; mixing the composite polyester powder and modified polytetrafluoroethylene evenly to obtain a sealing filler; B2. Maintain the sealing filler at a pressure of 50-100 MPa for 30 minutes to obtain a preform; and sinter the preform at a high temperature to obtain a corrosion-resistant centrifugal water pump sealing filler.

10. The method for preparing a corrosion-resistant centrifugal water pump sealing filler according to claim 9, characterized in that: In step B2, the high temperature sintering temperature is 360-370°C and the high temperature sintering pressure is 30-50MPa; during the sintering process, the sintering temperature is reached at a constant heating rate of 60°C, and then restored to room temperature at a constant heating rate of 30°C.

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