Anti-aging filler sheet for cooling tower and preparation method of anti-aging filler sheet

Abstract

The invention discloses an anti-aging filler sheet for a cooling tower and a preparation method of the anti-aging filler sheet, and belongs to the technical field of cooling tower filler sheets. Carbon nano tube composite carrier powder is subjected to a plasma surface modification technology to obtain hydroxylated carrier powder, and the hydroxylated carrier powder is subjected to a chemical grafting adsorption effect to obtain the anti-aging filler sheet for the cooling tower. Combining an anti-aging coupling agent with the hydroxylated carrier powder to obtain organic-inorganic composite anti-aging agent basalt fiber powder; according to the anti-aging filler sheet for the cooling tower, the organic-inorganic composite anti-aging agent is added, N-phenyl-p-phenylenediamine is grafted to the surface of carbon nanotube composite carrier powder through chemical bonding of the silane coupling agent, stable loading and slow release of the organic anti-aging agent are achieved, migration of the organic anti-aging agent under the high-temperature condition is reduced, and the anti-aging performance of the cooling tower is improved. The anti-aging stability of the filler sheet is improved, and the service life of the filler sheet is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of aging-resistant fillers, and particularly relates to an aging-resistant filler sheet for a cooling tower and a preparation method thereof. Background Art

[0002] Age-resistant packing sheets for cooling towers are key components for improving heat dissipation efficiency. They are typically made of heat- and age-resistant materials, such as polyvinyl chloride (PVC) or glass fiber reinforced plastic (GRP), which offer excellent chemical and weather resistance. The packing sheets are designed to increase the contact area between the cooling water and the air, thereby improving heat exchange efficiency. They typically feature a special corrugated shape that creates a thin film of water flow, increasing contact time with the air while reducing splashing losses. The packing's ageing resistance ensures stable performance even under long-term exposure to sunlight and weather conditions, extending the overall service life of the cooling tower.

[0003] Chinese invention patent application publication number CN113004600A discloses a cooling tower filler and its preparation process. The filler includes a cooling layer for cooling the liquid. The cooling layer is provided with honeycomb through holes for convective contact between the liquid and air. The filler is made of a new polyethylene plastic. The new polyethylene plastic is mainly made of high-density polyethylene, polybutadiene, polyethylene terephthalate, modified ceramic micropowder and modified zinc oxide. The obtained cooling tower plastic filler has better anti-aging ability and stronger durability.

[0004] The above scheme uses benzophenone-modified ceramic micropowder and zinc oxide to form an organic-inorganic anti-aging system to improve the anti-aging performance of the filler sheet. However, benzophenone combines with the ceramic micropowder through physical adsorption. In the steel, metallurgy and other industries, the water inlet temperature of the cooling tower is generally high, reaching 60-80°C. Organic anti-aging agents such as benzophenone will migrate, resulting in a decrease in the anti-aging stability of the filler sheet. Summary of the Invention

[0005] The purpose of the present invention is to provide an aging-resistant filler sheet for a cooling tower and a preparation method thereof, so as to solve the problem that the organic anti-aging agent of the cooling tower filler sheet is easy to migrate and the anti-aging stability is reduced under harsh environments such as high water inlet temperature.

[0006] The present invention utilizes the high thermal conductivity of boron nitride nanosheets to load zinc oxide, and then in-situ grows carbon nanotubes, thereby significantly improving the overall thermal conductivity; N-phenyl-p-phenylenediamine is then grafted onto the surface of the carbon nanotube composite carrier powder through chemical bonding with a silane coupling agent, thereby reducing the migration of organic anti-aging agents; nano-silicon carbide is added to enhance rigidity and hybridize with basalt fiber powder to improve the overall mechanical properties, thereby achieving high elasticity, high thermal conductivity and excellent aging resistance of aging-resistant filler sheets for cooling towers.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for preparing an aging-resistant filler sheet for a cooling tower comprises the following steps:

[0009] Step 1: The carbon nanotube composite carrier powder is subjected to plasma surface modification technology to obtain hydroxylated carrier powder; through the synergistic effect of chemical grafting and π-π adsorption, the anti-aging coupling agent and the hydroxylated carrier powder are ultrasonically dispersed and refluxed in an ethanol system, and then washed, dried and sieved to achieve covalent bond fixation to obtain an organic-inorganic composite anti-aging agent.

[0010] Step 2: High-density polyethylene, polybutadiene, ethylene-acrylic acid copolymer and polyethylene terephthalate are mixed and heated until melted, and then an organic-inorganic composite anti-aging agent and silicon carbide hybrid basalt fiber powder are added and mixed evenly, and then transferred to a twin-screw extruder for extrusion molding to obtain an aging-resistant filler sheet for cooling towers.

[0011] Furthermore, the mass ratio of high-density polyethylene, polybutadiene, ethylene-acrylic acid copolymer, polyethylene terephthalate, organic-inorganic composite anti-aging agent and silicon carbide hybrid basalt fiber powder is 35-45:5-8:2-3:15-20:8-15:16-20.

[0012] Furthermore, the organic-inorganic composite anti-aging agent is prepared by the following steps:

[0013] The composite powder dispersion and the anti-aging coupling agent solution are added into a spherical condenser and mixed evenly, refluxed at 60-80° C., cooled and filtered, the filter cake is washed, dried, ground, and passed through a 600-mesh sieve to obtain an organic-inorganic composite anti-aging agent.

[0014] Furthermore, the volume ratio of the composite powder dispersion to the anti-aging coupling agent solution is 100-160:60-100.

[0015] Furthermore, the composite powder dispersion is prepared by the following steps:

[0016] The hydroxylated carrier powder was added into a 95 wt % ethanol aqueous solution and ultrasonicated for 30-40 min to obtain a composite powder dispersion.

[0017] Furthermore, the usage ratio of the hydroxylated carrier powder and the ethanol aqueous solution is 4-8 g: 80-160 mL.

[0018] Furthermore, the anti-aging coupling agent solution is prepared by the following steps:

[0019] N-phenyl-p-phenylenediamine and silane coupling agent KH560 are refluxed in an oil bath at 120-140° C. for 2-3 hours, 95 wt % ethanol aqueous solution is added, and ultrasonication is performed for 20-30 minutes to obtain an anti-aging coupling agent solution.

[0020] Furthermore, the usage ratio of N-phenyl-p-phenylenediamine, silane coupling agent and ethanol aqueous solution is 1.6-2 g: 1.6-2 g: 160-200 mL.

[0021] Furthermore, the hydroxylated carrier powder is prepared by the following steps:

[0022] The carbon nanotube composite carrier powder is added into a plasma reaction chamber, oxygen is introduced at a pressure of 30-50 Pa and a radio frequency power of 60-80 W, the reaction is carried out for 20-30 minutes, and the powder is taken out after cooling to obtain a hydroxylated carrier powder.

[0023] Furthermore, the carbon nanotube composite carrier powder is prepared by the following steps:

[0024] Inorganic anti-aging powder and anhydrous ethanol are added to a reactor, and then nickel acetate is added. The mixture is ultrasonicated for 6-8 hours, stirred for 18-24 hours, and transferred to a rotary evaporator for drying to obtain a precursor mixture. The precursor mixture is ground and passed through an 800-mesh sieve. Under argon protection, the mixture is reacted at 500-600°C for 15-20 minutes. After heating to 660-700°C, methane gas is introduced and reacted for 8-10 minutes. The mixture is ground and passed through a 600-mesh sieve to obtain a carbon nanotube composite carrier powder.

[0025] Furthermore, the usage ratio of the inorganic anti-aging powder, anhydrous ethanol and nickel acetate is 30-40 g: 6-8 L: 2-2.4 g.

[0026] Furthermore, the inorganic anti-aging powder is prepared by the following steps:

[0027] Hydroxylated boron nitride nanosheets and deionized water are added to a reactor, ultrasonically dispersed for 1-2 hours, and then a 6wt% zinc nitrate hexahydrate aqueous solution is added and stirred for 1-2 hours. The pH value is adjusted to 9-11 with a sodium hydroxide solution, and the mixture is reacted at 120-140°C for 6-12 hours. The mixture is filtered, the filter cake is washed, dried, and transferred to a tubular heating furnace. The mixture is kept warm at 600°C under argon protection for 2-3 hours, naturally cooled to room temperature, ground, and passed through an 800-mesh sieve to obtain an inorganic anti-aging powder.

[0028] Furthermore, the usage ratio of the hydroxylated boron nitride nanosheets, deionized water and zinc nitrate hexahydrate aqueous solution is 40-48 g: 40-48 L: 4-4.4 L.

[0029] Furthermore, hydroxylated boron nitride nanosheets are prepared by the following steps:

[0030] Adding boron nitride nanosheets and hydrogen peroxide into a reaction kettle, reacting at 100-120° C. for 2-3 hours, filtering and drying to obtain hydroxylated boron nitride nanosheets.

[0031] Furthermore, the usage ratio of the boron nitride nanosheets and hydrogen peroxide is 40-48 g:12-16 L.

[0032] Furthermore, silicon carbide hybrid basalt fiber powder is prepared by the following steps:

[0033] Nano-silicon carbide is modified by silane coupling agent KH550 to obtain modified nano-silicon carbide powder, and basalt fiber powder is modified by silane coupling agent KH560 to obtain modified basalt fiber powder; the modified nano-silicon carbide powder and the modified basalt fiber powder are combined by reacting the grafted amino group with the epoxy group to obtain silicon carbide hybrid basalt fiber powder.

[0034] Beneficial effects of the present invention:

[0035] 1. The aging-resistant filler sheet for cooling towers of the present invention is added with an organic-inorganic composite anti-aging agent, and N-phenyl-p-phenylenediamine is grafted to the surface of the carbon nanotube composite carrier powder through chemical bonding with a silane coupling agent, thereby achieving stable loading and slow release of the organic anti-aging agent, reducing its migration under high temperature conditions, improving the anti-aging stability of the filler sheet, and helping to extend the service life of the filler sheet.

[0036] 2. The organic-inorganic composite anti-aging agent in the present invention uniformly loads zinc oxide nanoparticles on the surface of boron nitride nanosheets, and then generates carbon nanotubes on the surface. The thermal conductivity of the boron nitride nanosheets and the interface optimization of zinc oxide and carbon nanotubes jointly construct a low thermal resistance thermal conductivity network, thereby improving the overall thermal conductivity of the filler sheet; the composite structure of N-phenyl-p-phenylenediamine and inorganic anti-aging powder simultaneously delays the photo-oxidation aging of the matrix through ultraviolet absorption and physical shielding, thereby extending the service life of the filler sheet under ultraviolet irradiation; the organic-inorganic composite anti-aging agent can also improve the bending elastic modulus and notch impact strength of the filler sheet by deflecting the crack propagation path.

[0037] 3. The silicon carbide hybrid basalt fiber powder in the present invention can improve the mechanical properties and durability of the filler sheet. The basalt fiber powder provides support, and the nano-silicon carbide particles attached to the surface can increase the interfacial bonding strength between the basalt fiber powder and the matrix material. Nano-silicon carbide can also improve the thermal conductivity of the fiber and further enhance the high-temperature resistance of the filler sheet, making it suitable for the high inlet water temperature of the cooling tower. DETAILED DESCRIPTION

[0038] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] Example 1: A method for preparing an aging-resistant filler sheet for a cooling tower, comprising the following steps:

[0040] S1: Add 40g of boron nitride nanosheets and 12L of hydrogen peroxide into a reactor, react at 100°C for 2h, filter and dry to obtain hydroxylated boron nitride nanosheets; add 40g of hydroxylated boron nitride nanosheets and 40L of deionized water into a reactor, ultrasonically disperse for 1h, then add 4L of 6% by mass zinc nitrate hexahydrate aqueous solution, stir for 1h to obtain a mixed solution, and adjust the pH value to 9 with sodium hydroxide solution; transfer the mixed solution to a reactor, react at 120°C for 6h, filter, wash with deionized water and ethanol, vacuum dry at 60°C, transfer to a tubular heating furnace, keep warm at 600°C under argon protection for 2h, naturally cool to room temperature, grind, and pass through an 800-mesh sieve to obtain an inorganic anti-aging powder.

[0041] Hydrogen peroxide, as an oxidant, reacts with the surface of boron nitride at high temperature, introducing hydroxyl-OH groups. Hydrophilic active sites are formed on the surface of hydroxylated boron nitride nanosheets, enhancing their dispersibility and binding ability with subsequent zinc precursors. Zinc hydroxide is grown on its surface through hydrothermal synthesis, ultimately forming a composite structure with uniformly loaded zinc oxide nanoparticles.

[0042] S2: Add 30g of inorganic anti-aging powder and 6L of anhydrous ethanol to the reactor, then add 2g of nickel acetate, ultrasonicate for 6h, stir for 18h, transfer to a rotary evaporator for drying to obtain a precursor mixture; grind the precursor mixture, pass through an 800-mesh sieve, and under argon protection, heat to 500℃ and react for 15min, then continue to heat to 660℃ and introduce methane gas to react for 8min, grind and pass through a 600-mesh sieve to obtain a carbon nanotube composite carrier powder.

[0043] Boron nitride nanosheets loaded with zinc oxide are used as a substrate, nickel is used as a catalyst, and methane is used as a carbon source. The substrate / catalyst mixture prepared by the impregnation method is reduced with hydrogen at 500-600°C. When the temperature is further increased to the cracking temperature of the carbon source, carbon nanotubes grow between the layers of the boron nitride nanosheets loaded with zinc oxide, acting as a "bridge" to bridge the layers together.

[0044] S3: Add 10g of carbon nanotube composite carrier powder into the plasma reaction chamber, introduce oxygen at a pressure of 30Pa and a radio frequency power of 60W, react for 20min, cool and take out to obtain hydroxylated carrier powder; reflux 1.6g of N-phenyl-p-phenylenediamine and 1.6g of silane coupling agent KH560 in an oil bath at 120°C for 2h, then add 160mL of 95% ethanol aqueous solution, and ultrasonicate for 20min to obtain an anti-aging coupling agent solution; add 4g of hydroxylated carrier powder to 80mL of 95% ethanol aqueous solution, and ultrasonicate for 30min to obtain a composite powder dispersion; add 100mL of the composite powder dispersion and 60mL of the anti-aging coupling agent solution into a spherical condenser, mix evenly, reflux at 60°C, cool and filter, wash the product with ethanol 3 times, dry, grind, and pass through a 600-mesh sieve to obtain an organic-inorganic composite anti-aging agent.

[0045] Hydroxyl groups are loaded on the surface of the carbon nanotube / boron nitride / zinc oxide composite through plasma treatment. The epoxy group of KH560 undergoes a nucleophilic ring-opening reaction with the amino group of N-phenyl-p-phenylenediamine at high temperature to form a covalent bond. The silanol in the anti-aging coupling agent condenses with the hydroxyl groups on the surface of the composite to also form a covalent bond. The benzene ring of N-phenyl-p-phenylenediamine is adsorbed on the surface of the carbon nanotube through π-π interaction, thereby fixing the anti-aging agent.

[0046] S4: 8 g of nano-silicon carbide and 200 mL of ethanol were added to a reactor, ultrasonically dispersed for 20 min, 0.5 mL of silane coupling agent KH550 was slowly added dropwise and stirred under constant temperature reflux for 30 min, washed three times by centrifugation with anhydrous ethanol, and vacuum dried at 60°C for 10 h to obtain modified nano-silicon carbide powder.

[0047] Ultrasonic wave breaks up the agglomeration of nano-SiC, silane coupling agent generates active silanol, the surface of nano-SiC is covalently bonded with silanol to form an organic modification layer, and stable modified nano-SiC powder is obtained by washing and drying.

[0048] S5: Add 20 g of basalt fiber powder with a length of 3 mm to 600 mL of 1% KH560 solution and soak for 2 h. After filtering, dry at 70°C for 30 min to obtain modified basalt fiber powder. Ultrasonic disperse 4 g of modified nano-silicon carbide powder in 300 mL of ethanol solution, add 20 g of modified basalt fiber powder, transfer to a constant temperature water bath at 60°C for 2 h, filter and rinse with ethanol three times, and dry at 60°C to constant weight to obtain silicon carbide hybrid basalt fiber powder.

[0049] KH560 is bonded to basalt fiber powder through silanol condensation to introduce epoxy groups; modified silicon carbide and modified fiber are combined through chemical bonds to form a "particle-fiber" hybrid structure, which is then washed to remove physically adsorbed impurities and dried to fix the hybrid interface.

[0050] S6: 35g of high-density polyethylene, 5g of polybutadiene, 2g of ethylene-acrylic acid copolymer and 15g of polyethylene terephthalate are mixed and heated until melted, and then 8g of an organic-inorganic composite anti-aging agent and 16g of silicon carbide hybrid basalt fiber powder are added and mixed evenly, and then transferred to a twin-screw extruder for extrusion molding to obtain an aging-resistant filler sheet for a cooling tower.

[0051] Example 2: A method for preparing an aging-resistant filler sheet for a cooling tower, comprising the following steps:

[0052] S1: 44 g of boron nitride nanosheets and 14 L of hydrogen peroxide were added to a reactor, reacted at 110° C. for 2.5 h, filtered and dried to obtain hydroxylated boron nitride nanosheets; 44 g of hydroxylated boron nitride nanosheets and 44 L of deionized water were added to a reactor, ultrasonically dispersed for 1.5 h, and then 4.2 L of a 6% by mass aqueous solution of zinc nitrate hexahydrate was added and stirred for 1.5 h to obtain a mixed solution, and the pH value was adjusted to 10 with sodium hydroxide solution; the mixed solution was transferred to a reactor, reacted at 130° C. for 9 h, filtered, washed with deionized water and ethanol, vacuum dried at 65° C., transferred to a tubular heating furnace, kept warm at 600° C. under argon protection for 2.5 h, naturally cooled to room temperature, ground, and passed through an 800-mesh sieve to obtain an inorganic anti-aging powder.

[0053] S2: Add 35g of inorganic anti-aging powder and 7L of anhydrous ethanol to the reactor, then add 2.2g of nickel acetate, ultrasonicate for 7h, stir for 21h, transfer to a rotary evaporator and dry to obtain a precursor mixture; grind the precursor mixture, pass through an 800-mesh sieve, and under argon protection, heat to 550℃ and react for 17.5min. Then continue to heat to 680℃ and introduce methane gas to react for 9min, grind and pass through a 600-mesh sieve to obtain a carbon nanotube composite carrier powder.

[0054] S3: Add 13g of carbon nanotube composite carrier powder into the plasma reaction chamber, introduce oxygen at a pressure of 40Pa and a radio frequency power of 70W, react for 25min, cool and take out to obtain hydroxylated carrier powder; reflux 1.8g of N-phenyl-p-phenylenediamine and 1.8g of silane coupling agent KH560 in an oil bath at 130°C for 2.5h, then add 180mL of 95% ethanol aqueous solution, and ultrasonicate for 25min to obtain an anti-aging coupling agent solution; add 6g of hydroxylated carrier powder to 120mL of 95% ethanol aqueous solution, and ultrasonicate for 35min to obtain a composite powder dispersion; add 130mL of the composite powder dispersion and 80mL of the anti-aging coupling agent solution into a spherical condenser, mix evenly, reflux at 70°C, cool and filter, wash the product with ethanol 4 times, dry, grind, and pass through a 600-mesh sieve to obtain an organic-inorganic composite anti-aging agent.

[0055] S4: 14 g of nano-silicon carbide and 250 mL of ethanol were added to a reactor, ultrasonically dispersed for 25 min, 1 mL of silane coupling agent KH550 was slowly added dropwise and stirred under constant temperature reflux for 35 min, washed with anhydrous ethanol by centrifugation 4 times, and vacuum dried at 65°C for 11 h to obtain modified nano-silicon carbide powder.

[0056] S5: Add 25 g of basalt fiber powder with a length of 3 mm to 700 mL of 1% KH560 solution and soak for 2.5 h. After filtering, dry at 75°C for 35 min to obtain modified basalt fiber powder. Ultrasonic disperse 4.5 g of modified nano-silicon carbide powder in 350 mL of ethanol solution, add 25 g of modified basalt fiber powder, transfer to a constant temperature water bath at 60°C for 2.5 h, filter and rinse with ethanol 4 times, and dry at 60°C to constant weight to obtain silicon carbide hybrid basalt fiber powder.

[0057] S6: 40g of high-density polyethylene, 6.5g of polybutadiene, 2.5g of ethylene-acrylic acid copolymer and 17.5g of polyethylene terephthalate are mixed and heated until melted, and then 11.5g of an organic-inorganic composite anti-aging agent and 18g of silicon carbide hybrid basalt fiber powder are added and mixed evenly, and then transferred to a twin-screw extruder for extrusion molding to obtain an aging-resistant filler sheet for a cooling tower.

[0058] Example 3: A method for preparing an aging-resistant filler sheet for a cooling tower, comprising the following steps:

[0059] S1: Add 48g of boron nitride nanosheets and 16L of hydrogen peroxide into a reactor, react at 120°C for 3h, filter and dry to obtain hydroxylated boron nitride nanosheets; add 48g of hydroxylated boron nitride nanosheets and 48L of deionized water into a reactor, ultrasonically disperse for 2h, then add 4.4L of 6% by mass zinc nitrate hexahydrate aqueous solution, stir for 2h to obtain a mixed solution, and adjust the pH value to 11 with sodium hydroxide solution; transfer the mixed solution to a reactor, react at 140°C for 12h, filter, wash with deionized water and ethanol, vacuum dry at 70°C, transfer to a tubular heating furnace, keep warm at 600°C under argon protection for 3h, naturally cool to room temperature, grind, and pass through an 800-mesh sieve to obtain an inorganic anti-aging powder.

[0060] S2: Add 40g of inorganic anti-aging powder and 8L of anhydrous ethanol to a reactor, then add 2.4g of nickel acetate, ultrasonicate for 8h, stir for 24h, transfer to a rotary evaporator and dry to obtain a precursor mixture; grind the precursor mixture, pass through an 800-mesh sieve, and under argon protection, heat to 600℃ and react for 20min, then continue to heat to 700℃ and introduce methane gas to react for 10min, grind and pass through a 600-mesh sieve to obtain a carbon nanotube composite carrier powder.

[0061] S3: Add 16g of carbon nanotube composite carrier powder into the plasma reaction chamber, introduce oxygen at a pressure of 50Pa and a radio frequency power of 80W, react for 30min, cool and take out to obtain hydroxylated carrier powder; 2g of N-phenyl-p-phenylenediamine and 2g of silane coupling agent KH560 are refluxed in an oil bath at 140°C for 3h, and then 200mL of 95% ethanol aqueous solution are added and ultrasonicated for 30min to obtain an anti-aging coupling agent solution; 8g of hydroxylated carrier powder is added to 160mL of 95% ethanol aqueous solution and ultrasonicated for 40min to obtain a composite powder dispersion; 160mL of the composite powder dispersion and 100mL of the anti-aging coupling agent solution are added to a spherical condenser and mixed evenly, refluxed at 80°C, cooled and filtered, and the product is washed with ethanol 5 times, dried, ground, and passed through a 600-mesh sieve to obtain an organic-inorganic composite anti-aging agent.

[0062] S4: 20 g of nano-silicon carbide and 300 mL of ethanol were added to the reactor, ultrasonically dispersed for 30 min, 1.5 mL of silane coupling agent KH550 was slowly added dropwise and stirred under constant temperature reflux for 40 min, washed by centrifugation with anhydrous ethanol 5 times, and vacuum dried at 70 ° C for 12 h to obtain modified nano-silicon carbide powder.

[0063] S5: 30 g of basalt fiber powder with a length of 3 mm was added to 800 mL of a 1% KH560 solution and soaked for 3 h. After filtering, the mixture was dried at 80°C for 40 min to obtain modified basalt fiber powder. 5 g of modified nano-silicon carbide powder was ultrasonically dispersed in 400 mL of ethanol solution, and then 30 g of modified basalt fiber powder was added. The mixture was transferred to a constant temperature water bath at 60°C for 3 h, filtered, rinsed with ethanol 5 times, and dried at 60°C to constant weight to obtain silicon carbide hybrid basalt fiber powder.

[0064] S6: 45g of high-density polyethylene, 8g of polybutadiene, 3g of ethylene-acrylic acid copolymer and 20g of polyethylene terephthalate are mixed and heated until melted, and then 15g of an organic-inorganic composite anti-aging agent and 20g of silicon carbide hybrid basalt fiber powder are added and mixed evenly, and then transferred to a twin-screw extruder for extrusion molding to obtain an aging-resistant filler sheet for a cooling tower.

[0065] In Examples 1 to 3, the boron nitride nanosheets were 10043-11-5 from Hubei Yamade Biopharmaceutical Co., Ltd.; the remaining raw materials were all commercially available products.

[0066] Comparative Example 1: The difference from Example 3 is that step S1 is not performed, the inorganic anti-aging powder is replaced by hydroxylated boron nitride nanosheets in step S2, and the other steps remain unchanged to prepare anti-aging filler sheets for cooling towers.

[0067] Comparative Example 2: The difference from Example 3 is that steps S1, S2 and S3 are not performed, the organic-inorganic composite anti-aging agent is replaced by N-phenyl-p-phenylenediamine in step S6, and the other steps remain unchanged to prepare an aging-resistant filler sheet for a cooling tower.

[0068] Comparative Example 3: The difference from Example 3 is that step S3 is not performed, the organic-inorganic composite anti-aging agent is replaced by carbon nanotube composite carrier powder in step S6, and the other steps remain unchanged to prepare an aging-resistant filler sheet for a cooling tower.

[0069] Comparative Example 4: The difference from Example 3 is that step S4 is deleted, and the silicon carbide hybrid basalt fiber powder is replaced by modified basalt fiber powder in step S6. The other steps remain unchanged to prepare an aging-resistant filler sheet for a cooling tower.

[0070] The aging-resistant filler sheets for cooling towers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were pressed and cut into 80 mm × 10 mm × 4 mm specimens. The thermal conductivity of the specimens was measured with reference to the standard ASTM D5470-06 for thermal conductivity of thermally conductive insulating materials. The mechanical properties of the specimens were measured with reference to the method specified in the standard GB / T 9341-2008. The specimens were subjected to irradiation at a wavelength of 313 nm and an irradiance of 0.72 / m 2 The aging resistance of the samples was measured after the samples were treated in a UV aging box for 48 hours; the notched impact strength of the samples was measured according to the method specified in the reference standard GB / ISO180-1A, and the results are shown in Table 1:

[0071] Table 1 Performance test results of aging-resistant filler sheets for cooling towers

[0072]

[0073]

[0074] As can be seen from Table 1, the performance of the aging-resistant filler sheets for cooling towers prepared in Examples 1 to 3 of the present invention is significantly better than that of the comparative example. The hydroxylated boron nitride nanosheets are the skeleton of the thermal conductive network, and their layered structure can form a continuous thermal conductive path. The loaded zinc oxide can optimize interfacial heat transfer. The carbon nanotubes are the core reinforcing phase of thermal conductivity, which synergistically reduces the interfacial thermal resistance, has good thermal conductivity, and improves the mechanical properties of the aging-resistant filler. Zinc oxide can also synergize with organic antioxidants to enhance the anti-aging performance of the aging-resistant filler.

[0075] In Comparative Example 1, the tensile strength decreased significantly after irradiation. Zinc oxide is an inorganic ultraviolet absorber and can effectively block the photodegradation of the polymer matrix by ultraviolet rays.

[0076] In Comparative Example 2, since the organic anti-aging agent N-phenyl-p-phenylenediamine is used to replace the organic-inorganic composite anti-aging agent, the organic anti-aging agent can only play an anti-aging role in the polyethylene matrix and does not improve the mechanical properties of the polyethylene matrix. Therefore, the bending elastic modulus and tensile strength in Comparative Example 2 decrease, and since it does not contain zinc oxide, it cannot produce a synergistic effect with the organic anti-aging agent, and the aging resistance is reduced.

[0077] In Comparative Example 3, since the organic anti-aging agent N-phenyl-p-phenylenediamine was not grafted on the surface of the carbon nanotube composite carrier powder, the organic anti-aging agent can effectively slow down the aging reaction of the polyethylene matrix, and the inorganic anti-aging agent has limited improvement on the anti-aging performance of the polyethylene matrix. Therefore, the mechanical properties of Comparative Example 3 are significantly reduced after irradiation ultraviolet aging treatment.

[0078] In Comparative Example 4, since no modified nano-silicon carbide powder was added, a multi-level reinforcement structure of "fiber-silicon carbide-matrix" could not be formed, resulting in a decrease in the mechanical properties of Comparative Example 4.

[0079] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing an aging-resistant filler sheet for a cooling tower, characterized in that: The steps include: Step 1: The carbon nanotube composite carrier powder is surface modified by plasma to obtain a hydroxylated carrier powder, and the anti-aging coupling agent and the hydroxylated carrier powder are combined by chemical grafting and π-π adsorption synergistic action to obtain an organic-inorganic composite anti-aging agent; Step 2: High-density polyethylene, polybutadiene, ethylene-acrylic acid copolymer and polyethylene terephthalate are mixed and heated until melted, and then an organic-inorganic composite anti-aging agent and silicon carbide hybrid basalt fiber powder are added and mixed evenly, and then transferred to a twin-screw extruder for extrusion molding to obtain an aging-resistant filler sheet for cooling towers.

2. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 1, wherein: The mass ratio of the high-density polyethylene, polybutadiene, ethylene-acrylic acid copolymer, polyethylene terephthalate, organic-inorganic composite anti-aging agent and silicon carbide hybrid basalt fiber powder in step 2 is 35-45:5-8:2-3:15-20:8-15:16-20.

3. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 1, wherein: The organic-inorganic composite anti-aging agent in step 1 is prepared by the following steps: The hydroxylated carrier powder is added to a 95wt% ethanol aqueous solution and ultrasonicated for 30-40 minutes to obtain a composite powder dispersion; the composite powder dispersion and the anti-aging coupling agent solution are added to a spherical condenser and mixed evenly, refluxed at 60-80°C, cooled and filtered, and the filter cake is washed, dried, ground, and passed through a 600-mesh sieve to obtain an organic-inorganic composite anti-aging agent; The dosage ratio of the hydroxylated carrier powder and the ethanol aqueous solution is 4-8 g: 80-160 mL; the volume ratio of the composite powder dispersion and the anti-aging coupling agent solution is 100-160: 60-100.

4. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 3, wherein: The anti-aging coupling agent solution is prepared by the following steps: N-phenyl-p-phenylenediamine and silane coupling agent KH560 were refluxed in an oil bath at 120-140°C for 2-3 hours, and then a 95wt% ethanol aqueous solution was added and ultrasonicated for 20-30 minutes to obtain an anti-aging coupling agent solution; The usage ratio of the N-phenyl-p-phenylenediamine, the silane coupling agent and the ethanol aqueous solution is 1.6-2 g: 1.6-2 g: 160-200 mL.

5. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 3, wherein: The hydroxylated carrier powder is prepared by the following steps: The carbon nanotube composite carrier powder is added into a plasma reaction chamber, oxygen is introduced at a pressure of 30-50 Pa and a radio frequency power of 60-80 W, the reaction is carried out for 20-30 minutes, and the powder is taken out after cooling to obtain a hydroxylated carrier powder.

6. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 5, characterized in that: The carbon nanotube composite carrier powder is prepared by the following steps: Adding inorganic anti-aging powder and anhydrous ethanol to a reaction kettle, then adding nickel acetate, ultrasonicating for 6-8 hours, stirring for 18-24 hours, and transferring to a rotary evaporator for drying to obtain a precursor mixture; grinding the precursor mixture, passing through an 800-mesh sieve, reacting at 500-600°C for 15-20 minutes under argon protection, heating to 660-700°C, introducing methane gas, reacting for 8-10 minutes, grinding, and passing through a 600-mesh sieve to obtain a carbon nanotube composite carrier powder; The usage ratio of the inorganic anti-aging powder, anhydrous ethanol and nickel acetate is 30-40g:6-8L:2-2.4g.

7. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 6, characterized in that: The inorganic anti-aging powder is prepared by the following steps: Add hydroxylated boron nitride nanosheets and deionized water into a reactor, ultrasonically disperse for 1-2 hours, then add 6wt% zinc nitrate hexahydrate aqueous solution, stir for 1-2 hours, adjust the pH value to 9-11 with sodium hydroxide solution, react at 120-140℃ for 6-12 hours, filter, wash the filter cake, dry it, transfer it to a tubular heating furnace, keep it at 600℃ under argon protection for 2-3 hours, cool it naturally to room temperature, grind it, and pass it through an 800-mesh sieve to obtain an inorganic anti-aging powder; The dosage ratio of the hydroxylated boron nitride nanosheets, deionized water and zinc nitrate hexahydrate aqueous solution is 40-48 g: 40-48 L: 4-4.4 L.

8. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 7, wherein: The hydroxylated boron nitride nanosheets are prepared by the following steps: Adding boron nitride nanosheets and hydrogen peroxide into a reaction kettle, reacting at 100-120°C for 2-3 hours, filtering and drying to obtain hydroxylated boron nitride nanosheets; The usage ratio of the boron nitride nanosheets and hydrogen peroxide is 40-48 g:12-16 L.

9. The method for preparing an aging-resistant filler sheet for a cooling tower according to claim 1, wherein: The silicon carbide hybrid basalt fiber powder in step 2 is prepared by the following steps: Nano-silicon carbide is modified by silane coupling agent KH550 to obtain modified nano-silicon carbide powder, and basalt fiber powder is modified by silane coupling agent KH560 to obtain modified basalt fiber powder; the modified nano-silicon carbide powder and the modified basalt fiber powder are combined by reacting the grafted amino group with the epoxy group to obtain silicon carbide hybrid basalt fiber powder.

10. An aging-resistant filler sheet for a cooling tower, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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