Prestressed structural steel strand for wind tower and preparation process of prestressed structural steel strand

Abstract

The invention relates to the field of steel strand protection, and particularly discloses a prestressed structural steel strand for a wind tower and a preparation process of the prestressed structural steel strand. The preparation technology of the prestressed structural steel strand for the wind tower comprises the steps that S1, oil coating is conducted, specifically, a composite lubricant and base oil with the weight ratio being (1.5-2): 100 are mixed to obtain coating oil, then a steel strand body is coated with the coating oil, and an oil-coated body with the coating amount being 15-30 g / m is obtained; s2, extruding a sheath, wherein the sheath is prepared from the following raw materials in parts by weight: 65-70 parts of common polyethylene; 20 to 35 parts of high density polyethylene; 5-10 parts of a toughening agent; 2-3 parts of a lubricant; 0.5 to 0.6 part of a flame retardant-light stabilizer; and 0.25 to 0.35 part of an ultraviolet absorption-light stabilizer. The prestressed structural steel strand has the advantages of low grease coating amount, high sheath flatness and excellent protection capability, light-oxygen aging resistance and corrosion resistance are both at a high level, and the prestressed structural steel strand has high practicability and durability.

Description

Technical Field

[0001] The present application relates to the technical field of steel strand protection, and in particular to a prestressed structural steel strand for wind towers and a preparation process thereof. Background Art

[0002] A wind tower is a structure composed of steel components such as tower sections, steel strands, insulators, ground anchors, and anemometer brackets. It is used to install wind measuring instruments. It has a precise design, light weight, a small span, and is reinforced with prestressed structural steel strands. As a result, it has the advantages of strong wind resistance, not easy to collapse in droughts and wind disasters, and a safe and reliable structure. Therefore, steel strands play a very important role in the reinforcement of wind towers.

[0003] The steel strands used in wind towers are typically composed of twisted steel wires, which are then coated with anti-rust grease. A polymer mixture is then extruded onto the grease layer and allowed to solidify until a sheath forms on the outside of the main body. The sheath is typically made of polyethylene, toughening agents, antioxidants, and anti-aging agents. As requirements for the performance of steel strands become increasingly stringent, researchers have added high-density polyethylene (HDPE) to the sheath. HDPE has superior hardness, tensile strength, and creep properties to low-density polyethylene (LDPE). It also offers superior wear resistance, electrical insulation, toughness, and cold resistance. At room temperature, it is insoluble in any organic solvents and resistant to corrosion from acids, alkalis, and various salts, significantly improving the overall performance of the sheath.

[0004] At present, some researchers have proposed that although the anti-rust grease coated on the outside of the main body can effectively lubricate and protect the main body of the steel strand, the current coating amount (≥40g / m) is too large and the grease layer is thick, which is not conducive to the close fit between the sheath and the main body, making the sheath less secure when fixed to the periphery of the main body. During use, the sheath may shift or even slip. Therefore, steel strands with low grease coating amount (≤30g / m) have gradually become popular steel strand categories. However, this brings new problems. Although the low coating amount can ensure that the sheath does not shift as much as possible after curing, during the sheath preparation process, the low coating amount cannot ensure a good lubrication effect on the surface of the steel strand during melt extrusion, which will lead to poor extrusion, especially when adding high-density polyethylene with general dispersion flow effect. The surface flatness of the final sheath is insufficient. In addition, the low coating amount reduces the antioxidant protection of the steel strand body. In summary, the low coating amount will affect the protective effect of the sheath in various aspects. Furthermore, researchers have found that due to the limited amount of lubricant added to the sheath, it is unrealistic to expect to achieve good lubrication by adding large amounts of lubricant to the sheath material. Consequently, due to these various issues, developing a prestressed structural steel strand with low grease application, excellent sheath flatness, and superior protective properties has become a challenging problem. Summary of the Invention

[0005] In order to solve the above technical problems, the present application provides a prestressed structural steel strand for a wind tower and a preparation process thereof.

[0006] In a first aspect, the present application provides a preparation process for prestressed structural steel strands for wind towers, comprising the following steps: S1. Oiling: S1. Oiling: A composite lubricant with a weight ratio of (1.5-2):100 is mixed with a base oil to obtain a coating oil, and then the steel strand body is coated to obtain an oiled body with a grease coating amount of 15-30 g / m. The composite lubricant is prepared by the following method: I. Sodium molybdate dihydrate and thiourea are mixed, reacted at a temperature of 160-200°C for 20-30h, cooled, washed, and dried to obtain lubricant body particles; II. Dithiophosphate-O,O-diisooctyl ester zinc salt is blended with the lubricant body particles, reacted, cooled, centrifuged, filtered, washed, and dried to obtain a composite lubricant. S2. Extruded sheath: The raw materials used for the sheath are melt-blended and then extruded onto the surface of the oil-coated main body, cooled, dried, and wound to obtain a prestressed structural steel strand with a sheath thickness of 1.8-2 mm. The raw materials used for the sheath include the following components in parts by weight: 65-70 parts of ordinary polyethylene; 20-35 parts of high-density polyethylene; 5-10 parts of toughening agent; 2-3 parts of lubricant; 0.5-0.6 parts of flame retardant-light stabilizer; 0.25-0.35 parts of ultraviolet absorption-light stabilizer; the structural formula of the flame retardant-light stabilizer is: ; The structural formula of the ultraviolet absorption-light stabilizer is: .

[0007] By adopting the above technical solution, the present application first uses a mixture of sodium molybdate dihydrate and thiourea, and reacts at a certain temperature and time to obtain particles with multiple active binding sites and an inorganic layered structure. Due to its layered structure, it can play a good anti-friction and lubrication effect when stacked between multiple of the above particles. At the same time, the present application also introduces dithiophosphate-O,O-diisooctyl ester zinc salt with antioxidant effect on multiple active sites of the particles and combines it with the lubricant main body particles to obtain a composite lubricant with both antioxidant and lubricating capabilities. After adding it to the base oil and then coating it, it can significantly improve the antioxidant capacity and anti-friction effect of the oil-coated main body. On this basis, the present application successfully reduces the amount of grease coating, which not only reduces the possibility of relative slippage between the sheath and the steel strand body after curing, but also improves the flatness of the sheath surface.

[0008] Antioxidants are added to the raw materials used in existing sheaths to increase the service life of the sheaths. In addition, in order to ensure the durability and stability of the antioxidant ability, large molecular antioxidants are generally selected. Due to their poor dispersion, they are easy to agglomerate in the polyethylene system. In addition, the low grease coating amount of this application will make the extrusion problem more obvious. Therefore, this application removes the antioxidants from the raw materials used in the sheaths, and uses the antioxidant effect of the composite lubricant to meet the overall antioxidant requirements of the steel strand. Removing the antioxidants from the raw materials used in the sheaths not only does not affect the overall antioxidant ability, but also further improves the smoothness of the sheath surface.

[0009] The present application also prepares a flame retardant-light stabilizer and an ultraviolet absorption-light stabilizer with two functions, and adds them to the raw materials used for the sheath, making full use of the synergistic effect and multifunctionality of the two additives, thereby achieving the dual goals of reducing the amount and type of additives used in the system and improving the protective ability of the sheath, smoothly improving the uniformity of the dispersion of the raw materials used in the sheath within the system, optimizing the extrusion effect of the raw materials used in the sheath, and significantly improving the anti-aging effect of the sheath.

[0010] In summary, due to various factors, the prestressed structural steel strand of the present application has low grease coating amount, high sheath flatness and excellent protective ability. During preparation, the extrusion effect of the raw materials used for the sheath is good. During use, the possibility of relative slippage between the sheath and the main body is low. The protective effect of the sheath is good, and the resistance to light and oxygen aging and corrosion resistance are at a high level. It has high practicality and durability.

[0011] Preferably, in step I, the reaction temperature is 180°C.

[0012] Preferably, in step I, the reaction time is 24 hours.

[0013] By adopting the above technical solution, the present application strictly controls the reaction temperature and reaction time when preparing the lubricant main particles, thereby reducing the specific surface area of the particles and optimizing their surface morphology, thereby increasing the number of active binding sites on the surface of particles of a certain mass, making it easier for them to combine with more dithiophosphate-O,O-diisooctyl ester zinc salt, thereby maximizing the antioxidant capacity of the composite lubricant.

[0014] Preferably, the coating oil in step S1 further comprises octyl zinc thiophosphate in an amount of 150-300 wt% of the amount of the composite lubricant.

[0015] By adopting the above technical solution, the present application also adds a certain amount of thiophosphate butyl octyl zinc salt for simultaneous use with the composite lubricant, further enhancing the overall antioxidant capacity without affecting the lubricating effect of the composite lubricant. The two also have a certain synergistic effect. Experimental data shows that even if the dosage of either substance is increased or used alone, the antioxidant effect of the two substances cannot be achieved by using them together in normal amounts. In addition, the present application strictly controls the amount of thiophosphate butyl octyl zinc salt added, enhancing the synergistic effect after mixing, and significantly improving the antioxidant properties of the coating oil.

[0016] Preferably, the amount of the thiophosphate butyl octyl zinc salt is 200wt% of the amount of the composite lubricant.

[0017] By adopting the above technical solution, the present application controls the amount of thiophosphate butyl octyl zinc salt to twice the weight of the composite lubricant. Experimental data show that the antioxidant capacity of the coating oil reaches the highest at this time, and the tensile strength decrease rate before and after aging is only 1.85%.

[0018] Preferably, the flame retardant-light stabilizer in step S2 is prepared by the following method: cyanuric chloride, N-butyl-2,2,6,6-tetramethyl-4-piperidinamine and sodium hydroxide are mixed and reacted, followed by extraction to obtain an organic phase, drying, and adding a hydrogen peroxide solution to the resultant, filtering to obtain a solid after the reaction, drying, adding tert-butyl hydroperoxide and cyclohexane to the resultant, filtering to remove the solid after the reaction, extracting to obtain an organic phase, drying, and the purified resultant is then blended with N,N'-bis(3-aminopropyl)ethylenediamine, reacted under the protection of an inert gas, cooled, separated to obtain an organic phase, washed, and dried to obtain a flame retardant-light stabilizer.

[0019] Preferably, the ultraviolet absorption-light stabilizer in step S2 is prepared by the following method: cyanuric chloride, N-butyl-2,2,6,6-tetramethyl-4-piperidinamine and sodium hydroxide are mixed and reacted, followed by extraction to obtain an organic phase, drying, and adding a hydrogen peroxide solution to the resultant, filtering to obtain a solid after the reaction, drying, adding hydroquinone to the resultant, recovering the azeotrope after the reaction, filtering to obtain a solid, washing, drying, and then mixing the resultant with chloroacetyl chloride to react, extracting to obtain an organic phase, removing the solvent, purifying, and finally mixing the purified resultant with tetramethylpiperidinol and tetrabutylammonium bromide to react, separating to obtain an organic phase, removing the solvent, and purifying to obtain the ultraviolet absorption-light stabilizer.

[0020] Since the steel strand of the present application is a component of a wind tower and is exposed to the natural environment, it will be subjected to relatively harsh environmental tests. Therefore, the present application adopts the above-mentioned technical solution to prepare a flame retardant-light stabilizer with cyclohexyloxy and piperidine amine, and also prepares a UV absorption-light stabilizer with intramolecular hydrogen bonds and piperidine amine, and adds the two together to the raw materials used for the sheath, which can achieve a good synergistic effect and greatly improve the flame retardancy, UV absorption ability and light stability of the sheath, so that the steel strand can be well adapted to its application environment and have excellent anti-aging ability.

[0021] Preferably, in step S2, the raw materials used for the sheath include the following components in parts by weight: 68 parts of ordinary polyethylene; 32 parts of high-density polyethylene; 7.5 parts of toughening agent; 2.5 parts of lubricant; 0.525 parts of flame retardant-light stabilizer; 0.315 parts of ultraviolet absorption-light stabilizer By adopting the above technical solution, the present application strictly controls the dosage ratio of each substance in the raw materials used for the sheath, thereby optimizing the protective effect of the sheath to the maximum extent.

[0022] In a second aspect, the present application provides a prestressed structural steel strand for a wind tower produced by the above-mentioned preparation process.

[0023] In summary, this application has the following beneficial technical effects: 1. The prestressed structural steel strand of the present application combines low grease coating, high sheath flatness, and excellent protective capabilities. During preparation, the raw materials used for the sheath have good extrusion effects. During use, the possibility of relative slippage between the sheath and the main body is low, the sheath has good protective effects, and its resistance to light, oxygen, aging, and corrosion is at a high level, making it highly practical and durable. 2. This application also adds a certain amount of thiophosphate butyl octyl zinc salt and uses it together with the composite lubricant, which can further enhance the overall antioxidant capacity without affecting the lubricating effect of the composite lubricant. DETAILED DESCRIPTION

[0024] Material Source Unless otherwise specified, the raw materials used in this application are all commercially available products, specifically: Sodium molybdate dihydrate was purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.; Thiourea was purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.; Dithiophosphoric acid-O,O-diisooctyl ester zinc salt was purchased from Ruifeng New Materials Co., Ltd., CAS No. 28629-66-5; Cyanuric chloride was purchased from Tianjin Damao Chemical Reagent Factory; N-Butyl-2,2,6,6-tetramethyl-4-piperidinamine was purchased from Jiangsu Suqian Liansheng Technology Co., Ltd.; Tert-butyl hydroperoxide was purchased from Tianjin Damao Chemical Reagent Factory; N,N'-Bis(3-aminopropyl)ethylenediamine was purchased from Tianjin Damao Chemical Reagent Factory; Tetramethylpiperidinol was purchased from Rongsheng New Material Technology Co., Ltd.; The base oil was purchased from Shandong Naibeichi Lubrication Technology Co., Ltd., with the product number 24030106 and SAE viscosity 32#; Ordinary polyethylene was purchased from Dongguan Julong Plastic Raw Materials Co., Ltd. with a melt flow rate of 2.0 g / 10 min; High-density polyethylene was purchased from Daqing Petrochemical Company with a melt flow rate of 0.53 g / 10 min; The toughening agent was ethylene-octene copolymer, purchased from ExxonMobil Chemical, POE grade 8201-8201; The lubricant was polytetrafluoroethylene micropowder purchased from Shandong Dongyue Chemical Co., Ltd. with a particle size of 5-10 μm; Zinc thiophosphate was purchased from Jinzhou Chenghua New Materials Co., Ltd. 2,6-di-tert-Butyl-p-cresol was purchased from Anhui Runtai Biotechnology Co., Ltd.; Tris(2,4-di-tert-butylphenyl)phosphite was purchased from Baiyundu Biotechnology Co., Ltd.; Antioxidant B225 was purchased from BASF, CAS No. 6683-19-8; Butylated 4-hydroxyanisole was purchased from Jiangsu Jiujia Biotechnology Co., Ltd.; UV absorber UV-328 was purchased from BASF, CAS No. 6683-19-8; HAS light stabilizer was purchased from BASF, CAS No. 71878-19-8; The flame retardant DODPE was purchased from Henan Yiquan Chemical Technology Co., Ltd., CAS No. 84852-53-9.

[0025] The present application is further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0026] Preparation Example 1.1 The preparation method of the composite lubricant comprises the following steps: I. 10 mol of sodium molybdate dihydrate and 50 mol of thiourea were mixed and dispersed in a mixture of ethanol and water in a volume ratio of 1:2. The mixture was stirred until completely dissolved and reacted at 200° C. for 20 h. After the reaction, the mixture was cooled to room temperature. After filtering out the liquid, the solid matter was washed with distilled water 5 times and then with anhydrous ethanol 3 times, and freeze-dried to obtain lubricant main particles. II. Disperse 200 L of diisooctyl dithiophosphate zinc salt in isopropanol and ultrasonicate in an ice-water bath for 5 h. Then add 1.08 kg of the lubricant main particles prepared in step I and continue to react for 48 h. After the reaction, wash the mixture with 60°C anhydrous ethanol and filter it with suction, repeating this process three times. Then wash it with distilled water and filter it with suction, repeating this process three times. Finally, dry it to obtain a composite lubricant.

[0027] Preparation Example 1.2 The preparation method of the composite lubricant comprises the following steps: I. 10 mol of sodium molybdate dihydrate and 50 mol of thiourea were mixed and dispersed in a mixture of ethanol and water in a volume ratio of 1:2. The mixture was stirred until completely dissolved and reacted at 160° C. for 30 h. After the reaction, the mixture was cooled to room temperature. After filtering out the liquid, the solid matter was washed with distilled water 5 times and then with anhydrous ethanol 3 times. The solid matter was freeze-dried to obtain lubricant main particles. II. Disperse 200 L of diisooctyl dithiophosphate zinc salt in isopropanol and ultrasonicate in an ice-water bath for 5 h. Then add 1.08 kg of the lubricant main particles prepared in step I and continue to react for 48 h. After the reaction, wash the mixture with 60°C anhydrous ethanol and filter it with suction, repeating this process three times. Then wash it with distilled water and filter it with suction, repeating this process three times. Finally, dry it to obtain a composite lubricant.

[0028] Preparation Example 2.1 The preparation method of the composite lubricant is different from that of Preparation Example 1.1 in that the reaction temperature in step I is 190° C., and the rest is the same as that of Preparation Example 1.1.

[0029] Preparation Example 2.2 The preparation method of the composite lubricant is different from that of Preparation Example 1.1 in that the reaction temperature in step I is 180°C, and the rest is the same as that of Preparation Example 1.1.

[0030] Preparation Example 2.3 The preparation method of the composite lubricant is different from that of Preparation Example 1.1 in that the reaction temperature in step I is 170°C, and the rest is the same as that of Preparation Example 1.1.

[0031] Preparation Example 2.4 The preparation method of the composite lubricant is different from that of Preparation Example 1.1 in that the reaction temperature in step I is 160°C, and the rest is the same as that of Preparation Example 1.1.

[0032] Preparation Example 3.1 The preparation method of the composite lubricant is different from that of Preparation Example 2.2 in that the reaction time in step I is 22 hours, and the rest is the same as that of Preparation Example 2.2.

[0033] Preparation Example 3.2 The preparation method of the composite lubricant is different from that of Preparation Example 2.2 in that the reaction time in step I is 24 hours, and the rest is the same as that of Preparation Example 2.2.

[0034] Preparation Example 3.3 The preparation method of the composite lubricant is different from that of Preparation Example 2.2 in that the reaction time in step I is 26 hours, and the rest is the same as that of Preparation Example 2.2.

[0035] Preparation Example 3.4 The preparation method of the composite lubricant is different from that of Preparation Example 2.2 in that the reaction time in step I is 28 hours, and the rest is the same as that of Preparation Example 2.2.

[0036] Preparation Example 3.5 The preparation method of the composite lubricant is different from that of Preparation Example 2.2 in that the reaction time in step I is 30 hours, and the rest is the same as that of Preparation Example 2.2.

[0037] Preparation Example 4 The preparation method of the flame retardant-light stabilizer comprises the following steps: 10 mol of cyanuric chloride was dissolved in toluene, 20 mol of N-butyl-2,2,6,6-tetramethyl-4-piperidinamine was added in an ice-water bath and mixed for 2 h, then 2 L of 30 wt% sodium hydroxide aqueous solution was added, the temperature was raised to 70 ° C and the reaction was continued for 14 h, then water and ethyl acetate were added in a volume ratio of 2:1 for extraction to obtain an organic phase, which was dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation and dissolved in methanol, ultrasonically dissolved, and stirred at 15 ° C for 10 min. 8 L of 30 wt% hydrogen peroxide solution was added to the resultant, and the reaction was carried out at 25 ° C for 30 h. After filtration, a solid was obtained, which was dried at 35 ° C for 8 h, and finally 240 g of tert-butyl was added to the resultant. Butyl hydroperoxide, 1.25L cyclohexane, 7.5L acetonitrile, 250mL water, 137g ferric sulfate and 1.1kg glacial acetic acid were stirred at 50°C for 0.5h, then the temperature was raised to 70°C, and 4.5L 30wt% hydrogen peroxide solution was added dropwise within 2h. After the addition was completed, the reaction was continued for 8h, and the temperature was naturally cooled to room temperature. The solid was filtered out, and dichloromethane and water were added for extraction to obtain an organic phase. The organic phase was rotary evaporated, vacuum dried, and the obtained product after column chromatography separation and purification was dispersed in xylene, and 11L 25wt% sodium hydroxide solution was added, and then mixed with 216g N,N'-bis(3-aminopropyl)ethylenediamine was blended, stirred and heated under the protection of inert gas and a pressure of 0.5 MPa. When the temperature reached 170°C, the pressure was increased to 1 MPa, and the reaction was kept warm for 10 hours. The mixture was then cooled to room temperature, and the organic phase was separated. The solvent was removed under reduced pressure, and ethyl acetate was added and the mixture was allowed to stand and separate to obtain an organic phase. The organic phase was washed with water twice and dried to obtain a flame retardant-light stabilizer.

[0038] Preparation Example 5 The preparation method of the ultraviolet absorption-light stabilizer comprises the following steps: 10 mol of cyanuric chloride was dissolved in toluene, and 20 mol of N-butyl-2,2,6,6-tetramethyl-4-piperidinamine was added in an ice-water bath and mixed for reaction for 2 hours. Subsequently, 2 L of 30 wt% sodium hydroxide aqueous solution was added, the temperature was raised to 70 ° C and the reaction was continued for 14 hours, and then water and ethyl acetate with a volume ratio of 2: 1 were added for extraction to obtain an organic phase, which was dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation and dissolved in methanol. Ultrasonic dissolution was performed and stirred at 15 ° C for 10 minutes. 3.6 L of chlorobenzene and 1.2 kg of anhydrous aluminum chloride were added to the resultant in an ice-water bath. After stirring for 30 minutes, 1.1 kg of hydroquinone was added and the reaction was carried out at 80 ° C for 4 hours. 3.6 L of 2 wt% hydrochloric acid solution was slowly added dropwise, and the chlorobenzene-water azeotrope was recovered by atmospheric distillation. The temperature was raised to 100 ° C, and the solid was filtered while hot. It was washed 3 times with 2 wt% hydrochloric acid solution, and the mixture was washed with water for 3 times. Wash 3 times, vacuum dry, and then mix the resultant with 38L dichloromethane, and add 1.28kg chloroacetyl chloride and 1.15kg triethylamine dropwise in an ice-water bath. After the addition is completed, heat to room temperature and mix and react for 6h. Add deionized water and dichloromethane to extract to obtain an organic phase, evaporate the solvent at 50°C, and purify by chromatography. Finally, mix the purified resultant with 50.8L toluene to obtain a reaction solution 1 for standby use. Disperse 1.1kg tetramethylpiperidinol in 80L toluene, heat and stir until completely dissolved, add 2L of 35wt% sodium hydroxide solution, 0.41kg tetrabutylammonium bromide and reaction solution 1, stir and react at 60°C for 6h, separate the liquid to obtain an organic phase, wash with hot water until neutral, evaporate the solvent, and purify by chromatography to obtain a UV absorber-light stabilizer.

[0039] Comparative Preparation Example 1 The difference from Preparation Example 1.1 is that in step I, the reaction temperature is 220°C and the reaction time is 16 h. The rest is the same as Preparation Example 1.1.

[0040] Comparative Preparation Example 2 The difference from Preparation Example 1.1 is that in step I, the reaction temperature is 140°C and the reaction time is 34 hours. The rest is the same as Preparation Example 1.1.

[0041] Example 1.1 A preparation process for a prestressed structural steel strand for a wind tower comprises the following steps: S1. Oiling: First, clean the surface of a 1×7 steel strand with a diameter of 18.90 mm and set aside. Then, mix 150 g of the composite lubricant prepared in Preparation Example 1.1 with 10 kg of base oil to obtain a coating oil. Then, coat the cleaned steel strand with the oil to obtain an oil coating of 30 g / m2. S2, extruded sheath: 65kg of ordinary polyethylene, 35kg of high-density polyethylene, 5kg of toughening agent, 3kg of lubricant, 0.5kg of flame retardant-light stabilizer obtained in Preparation Example 4 and 0.35kg of ultraviolet absorption-light stabilizer obtained in Preparation Example 5 were mixed to obtain the raw materials used for the sheath, and the mixture was dried in an oven at 60°C. The mixture was added to a twin-screw extruder together with the oiled body obtained in step S1 for sheath extrusion. The screw diameter was 120mm, the aspect ratio was 25:1, the screw speed was 310rpm, and the extrusion temperature was 150°C, 160°C, 180°C, 200°C, 200°C, 220°C, 240°C, 240°C, 240°C, 220°C, 200°C. After extrusion, the mixture was cooled, dried, and wound up to obtain a prestressed structural steel strand with a sheath thickness of 2mm.

[0042] Example 1.2 A preparation process for a prestressed structural steel strand for a wind tower comprises the following steps: S1. Oiling: First, clean the surface of a 1×7 steel strand with a diameter of 18.90 mm and set aside. Then, mix 200 g of the composite lubricant prepared in Preparation Example 1.2 with 10 kg of base oil to obtain a coating oil. Then, coat the cleaned steel strand with the oil to obtain an oil coating of 15 g / m2. S2, extruded sheath: 70kg of ordinary polyethylene, 20kg of high-density polyethylene, 10kg of toughening agent, 2kg of lubricant, 0.6kg of flame retardant-light stabilizer obtained in Preparation Example 4 and 0.25kg of ultraviolet absorption-light stabilizer obtained in Preparation Example 5 were mixed to obtain the raw materials used for the sheath, and dried in an oven at 60°C, and added together with the oiled body obtained in step S1 to a twin-screw extruder for sheath extrusion, the screw diameter being 120mm, the aspect ratio being 25:1, the screw speed being 310rpm, and the extrusion temperature being 150°C, 160°C, 180°C, 200°C, 200°C, 220°C, 240°C, 240°C, 240°C, 220°C, 200°C. After extrusion, the mixture was cooled, dried, and wound up to obtain a prestressed structural steel strand with a sheath thickness of 1.8mm.

[0043] Example 1.3 A preparation process for prestressed structural steel strands for wind towers, which differs from Example 1.1 in that: in step S2, the raw materials used for the sheath are 68 kg of ordinary polyethylene, 32 kg of high-density polyethylene, 7.5 kg of toughening agent, 2.5 kg of lubricant, 0.525 kg of the flame retardant-light stabilizer prepared in Preparation Example 4, and 0.315 kg of the ultraviolet absorption-light stabilizer prepared in Preparation Example 5; the rest are the same as in Example 1.1.

[0044] Examples 2.1-2.4 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that the composite lubricant prepared in Preparation Example 1.1 in step S1 is replaced by the composite lubricants prepared in Preparation Examples 2.1-2.4 respectively, and the rest is the same as Example 1.1.

[0045] Examples 3.1-3.5 A preparation process for prestressed structural steel strands for wind towers, which differs from Example 2.2 in that: in step S1, the composite lubricant prepared in Preparation Example 2.2 is replaced by the composite lubricants prepared in Preparation Examples 3.1-3.5 respectively, and the rest is the same as Example 2.2.

[0046] Example 4.1 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that 225 g of butyl octyl zinc thiophosphate is further added to blend with 150 g of the composite lubricant prepared in Preparation Example 1.1 and 10 kg of base oil; the rest is the same as Example 1.1.

[0047] Example 4.2 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that 300 g of butyl octyl zinc thiophosphate is further added to blend with 150 g of the composite lubricant prepared in Preparation Example 1.1 and 10 kg of base oil; the rest is the same as Example 1.1.

[0048] Example 4.3 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that 375 g of butyl octyl zinc thiophosphate is further added to blend with 150 g of the composite lubricant prepared in Preparation Example 1.1 and 10 kg of base oil; otherwise, the preparation process is the same as Example 1.1.

[0049] Example 4.4 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that 450 g of butyl octyl zinc thiophosphate is further added to blend with 150 g of the composite lubricant prepared in Preparation Example 1.1 and 10 kg of base oil; the rest is the same as Example 1.1.

[0050] Example 4.5 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that 300 g of 2,6-di-tert-butyl-p-cresol is further added to blend with 150 g of the composite lubricant prepared in Preparation Example 1.1 and 10 kg of base oil; otherwise, the preparation process is the same as Example 1.1.

[0051] Example 4.6 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that 300 g of tris(2,4-di-tert-butylphenyl)phosphite is further added to blend with 150 g of the composite lubricant prepared in Preparation Example 1.1 and 10 kg of base oil; otherwise, the preparation process is the same as Example 1.1.

[0052] Example 4.7 A preparation process for prestressed structural steel strand for wind towers, which differs from Example 1.1 in that 300 g of antioxidant B225 is further added to blend with 150 g of the composite lubricant prepared in Preparation Example 1.1 and 10 kg of base oil, and the rest is the same as Example 1.1.

[0053] Comparative Examples 1.1-1.2 The difference from Example 1.1 is that the composite lubricant prepared in Preparation Example 1.1 in step S1 is replaced by the composite lubricants prepared in Comparative Preparation Examples 1-2 respectively, and the rest is the same as Example 1.1.

[0054] Comparative Examples 2.1-2.2 The difference from Example 1.1 is that in step S1, the amounts of the composite lubricant prepared in Preparation Example 1.1 are 100 g and 400 g respectively, and the rest are the same as Example 1.1.

[0055] Comparative Examples 3.1-3.3 The difference from Example 1.1 is that the composite lubricant prepared in Preparation Example 1.1 in step S1 is replaced by equal amounts of diisooctyl dithiophosphate zinc salt, butylated 4-hydroxyanisole, and 2,6-di-tert-butylated 4-cresol, respectively, and the coating amount is 50 g / m. The rest is the same as Example 1.1.

[0056] Comparative Examples 4.1-4.4 The difference from Example 1.1 is that 150 g of the composite lubricant prepared in Preparation Example 1.1 in step S1 is replaced by 400 g of octyl zinc thiophosphate, 400 g of 2,6-di-tert-butyl-p-cresol, 400 g of tris(2,4-di-tert-butylphenyl)phosphite and 400 g of antioxidant B225, respectively. The rest is the same as Example 1.1.

[0057] Comparative Example 5.1 The difference from Example 1.1 is that in step S2, the flame retardant-light stabilizer prepared in Preparation Example 4 is removed, and the amount of the ultraviolet absorption-light stabilizer prepared in Preparation Example 5 is 0.85 kg. The rest is the same as Example 1.1.

[0058] Comparative Example 5.2 The difference from Example 1.1 is that in step S2, the ultraviolet absorber-light stabilizer prepared in Preparation Example 5 is removed, and the amount of the flame retardant-light stabilizer prepared in Preparation Example 4 is 0.85 kg. The rest is the same as Example 1.1.

[0059] Comparative Example 5.3 The difference from Example 1.1 is that in step S2, the flame retardant-light stabilizer prepared in Preparation Example 4 and the ultraviolet absorption-light stabilizer prepared in Preparation Example 5 are removed, and 0.5 kg of ultraviolet absorber UV-328, 0.5 kg of HAS light stabilizer and 0.5 kg of flame retardant DODPE are added. The rest are the same as Example 1.1.

[0060] Performance testing 1. Antioxidation test: Weigh 1.0±0.1 mg of sample and place it in a crucible. In a nitrogen atmosphere with a flow rate of 100 mL / min, heat the sample from room temperature to a set constant temperature at a heating rate of 30 K / min. Then, it is replaced by oxygen at a flow rate of 100 mL / min within 1 minute. The final oxygen pressure is stabilized at 3.5 MPa. A curve of heat flow rate changing with time at the set temperature is obtained. After data post-processing, the intersection point of the baseline extension line and the exothermic peak tangent line is obtained. The horizontal axis corresponding to this point corresponds to the oxidation induction period (OTT) of the sample. The samples are taken from the coating oil and base oil in the examples and comparative examples. The OTT of the base oil is used as a benchmark to calculate the OTT change rate of the coating oil and the base oil. The calculation formula is: R OTT %=(OTT 涂覆油 -OTT 基础油 ) / OTT 基础油 ×100%; 2. Anti-light and oxygen aging test: The test was conducted in accordance with the standard plastic laboratory light source exposure test method Part 2: Xenon arc lamp. The sheath formula specimens obtained in the embodiment and comparative example were prepared according to the size of the type I tensile specimen in the standard GB / T 1040-1992. The tensile strength reduction rate before and after aging was measured. The calculation formula is: R ts %=(ts 前 -ts 后 ) / ts 前 ×100%, using a 3kW UV light source with a wavelength of 310nm and an irradiation intensity of 110W / m 2 , the relative humidity of the aging box is 85±5%, the box temperature is 55±5℃, and the test time is 2000h; 3. Corrosion resistance test: The weight of the tensile specimens of the sheath formula I obtained in the embodiment and the comparative example was recorded, and then immersed in a 35wt% hydrochloric acid solution at room temperature. After immersion for 42 days, the specimens were taken out and the surface moisture was wiped clean with filter paper. The mass change rate of the specimens was calculated, R m %=(m前 -m 后 ) / m 前 ×100%; 4. Flame retardancy test: The sheaths obtained in the examples and comparative examples were made into dumbbell-shaped specimens of 75 mm × 2 mm, and then the limiting oxygen index (LOI) was tested on a limiting oxygen index analyzer according to the description in GB / T 2406.2-2009; 5. Simulation test: The wind towers obtained in the examples and comparative examples were cut with prestressed steel strands to obtain samples with a length of 5±0.1 cm. The exposed parts of the steel strands at both ends of the samples were also sheathed and extruded. The samples were placed in a temperature of 70±5°C, a humidity of 85±5%, and an irradiation intensity of 110W / m 2 In a closed treatment box with an oxygen concentration of not less than 97%, record the time T0 when the sheath first cracks (observe once every 1 hour).

[0061] Table 1 Performance test table

[0062] Data Analysis: As can be seen from Table 1, the coating oil obtained in Examples 1.1-1.2 has an OTT change rate of up to 484-486% compared with conventional base oil, and the tensile strength decrease rate of the sheath samples of Examples 1.1-1.2 in photo-oxidation aging is only 2.87-2.88%, the mass change rate in a corrosive environment is only 1.04-1.05%, and the limiting oxygen index is 28.3-28.5. The final prestressed steel strand for wind towers has a sheath that first cracked for 228-229 hours under harsh environment simulation, which proves that the prestressed structural steel strand of the present application has low grease coating amount, high sheath flatness and excellent protective ability. During the preparation, the extrusion effect of the raw materials used in the sheath is good. During use, the possibility of relative slippage between the sheath and the main body is low, the protective effect of the sheath is good, and the resistance to photo-oxidation aging and corrosion resistance are at a high level, with high practicality and durability.

[0063] The sheath sample of Example 1.3 has a lower rate of decrease in tensile strength during photo-oxidative aging and a lower rate of mass change in a corrosive environment than Example 1.1, and the limiting oxygen index is also improved. The time for the first cracking of the sheath of the prestressed steel strand for wind towers under harsh environment simulation is also longer than that of Example 1.1, which proves that the present application optimizes the protective effect of the sheath to the maximum extent by strictly controlling the ratio of the amount of each substance in the raw materials used in the sheath.

[0064] The difference between Examples 2.1-2.4 and Example 1.1 is that the composite lubricant obtained by combining the lubricant main particles prepared at different reaction temperatures with dithiophosphate-O,O-dioctyl zinc salt is replaced. The difference between Examples 3.1-3.5 and Example 2.2 is that the composite lubricant obtained by combining the lubricant main particles prepared at different reaction times with dithiophosphate-O,O-dioctyl zinc salt is replaced. The OTT change rate of the coating oil obtained in Example 2.2 is significantly higher than that of Examples 2.1 and Examples 2.3-2.4. The sheath of the prestressed steel strand for wind towers cracked for the first time under harsh environment simulation. The time is also longer. The OTT change rate of the coating oil obtained in Example 3.2 is significantly higher than that in Example 3.1 and Examples 3.3-3.5. The time for the first cracking of the sheath of the prestressed steel strand for wind towers under harsh environment simulation is also longer, which proves that the present application strictly controls the reaction temperature and reaction time when preparing the main particles of the lubricant, thereby reducing the specific surface area of the particles and optimizing their surface morphology, thereby increasing the number of active binding sites on the surface of particles of a certain mass, so that it can be combined with more dithiophosphate-O,O-diisooctyl ester zinc salt, thereby maximizing the antioxidant capacity of the composite lubricant.

[0065] The OTT change rate of the coating oil obtained in Examples 4.1-4.4 is significantly higher than that in Example 1.1, and the time for the first cracking of the sheath of the prestressed steel strand for wind towers under harsh environment simulation is also longer, which proves that the present application can further enhance the overall antioxidant capacity without affecting the lubricating effect of the composite lubricant by adding a certain amount of thiophosphate butyl octyl zinc salt and using it simultaneously with the composite lubricant.

[0066] In Examples 4.5-4.7, butyl octyl zinc thionate was replaced with other antioxidants. Although the OTT change rate of the obtained coating oil was higher than that of Example 1.1, it was much lower than that of Example 4.2, proving that the butyl octyl zinc thionate of the present application has a certain synergistic effect with the composite lubricant, which significantly improves the antioxidant properties of the coating oil.

[0067] The OTT change rate of the coating oil obtained in Comparative Examples 1.1-1.2 is significantly lower than that in Example 1.1, and the time for the first cracking of the sheath of the prestressed steel strand for wind towers under harsh environment simulation is also shorter, which proves that the present application strictly controls the reaction temperature and reaction time when preparing the main particles of the lubricant, thereby reducing the specific surface area of the particles and optimizing their surface morphology, thereby increasing the number of active binding sites on the surface of particles of a certain mass, making it easier for them to combine with more dithiophosphate-O,O-diisooctyl ester zinc salt, thereby improving the antioxidant capacity of the composite lubricant.

[0068] The OTT change rate of the coating oil obtained in Comparative Examples 2.1-2.2 is significantly lower than that in Example 1.1, and the time for the first cracking of the sheath of the prestressed steel strand for wind towers under harsh environment simulation is also shorter, proving that the present application significantly improves the overall antioxidant ability and basic smoothness of the sheath by controlling the amount of composite lubricant added.

[0069] Comparative Examples 3.1-3.3 replaced the composite lubricant and increased the coating amount at the same time, but the OTT change rate of the obtained coating oil was significantly lower than that of Example 1.1. The time for the first cracking of the sheath of the prestressed steel strand for wind towers under harsh environment simulation was still shortened, proving that the composite lubricant of the present application has both antioxidant and lubricating capabilities, and can significantly improve the antioxidant capacity and anti-friction effect of the oil-coated body while reducing the coating amount.

[0070] Comparative Examples 4.1-4.4 replaced the composite lubricant with butyl octyl zinc salt of thiophosphate and a conventional antioxidant, and increased the dosage of the antioxidant. However, the OTT change rate of the obtained coating oil was significantly lower than that of Example 1.1, and the time for the first cracking of the sheath of the prestressed steel strand for wind towers under harsh environment simulation was still shortened. Even the OTT change rate of the coating oil of Comparative Example 4.1 was lower than that of Examples 4.2-4.4. This proves that the butyl octyl zinc salt of thiophosphate and the composite lubricant of the present application do have a synergistic effect. Even if the dosage is increased or either substance is used alone, the antioxidant effect of using both substances together in normal amounts cannot be achieved.

[0071] The tensile strength decrease rate of the sheath samples of comparative examples 5.1-5.3 during photo-oxidative aging and the mass change rate under corrosive environment are both higher than those of Example 1.1, and the limiting oxygen index is reduced. The time when the sheath of the prestressed steel strand for wind towers first cracks under harsh environment simulation is also much shorter than that of Example 1.1, which proves that the present application fully utilizes the synergistic effect of the flame retardant-light stabilizer and the ultraviolet absorption-light stabilizer with two functions, thereby achieving the dual purpose of reducing the amount and type of additives used in the system and improving the protective ability of the sheath, smoothly improving the uniformity of the dispersion of the raw materials used in the sheath within the system, optimizing the extrusion effect of the raw materials used in the sheath, and significantly improving the anti-aging effect of the sheath.

[0072] The embodiments of this specific implementation method are all preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A process for preparing prestressed structural steel strand for wind towers, characterized in that: The following steps are involved: S1. Oiling: A composite lubricant and a base oil are mixed in a weight ratio of (1.5-2):100 to obtain a coating oil, and then the steel strand body is coated with the coating oil to obtain an oil-coated body with a coating amount of 15-30 g / m. The composite lubricant is prepared by the following method: I. Sodium molybdate dihydrate and thiourea are mixed, reacted at a temperature of 160-200° C. for 20-30 hours, cooled, washed, and dried to obtain lubricant body particles; II. Dithiophosphoric acid-O,O-diisooctyl ester zinc salt is blended with the lubricant body particles, reacted, cooled, centrifuged, filtered, washed, and dried to obtain a composite lubricant; S2, extruded sheath: melt-blending the raw materials used for the sheath and then extruding it onto the surface of the oil-coated main body, cooling, drying, and winding to obtain a prestressed structural steel strand with a sheath thickness of 1.8-2 mm. The raw materials used for the sheath include the following components in parts by weight: 65-70 parts of ordinary polyethylene; 20-35 parts of high-density polyethylene; 5-10 parts of toughening agent; Lubricant 2-3 parts; Flame retardant-light stabilizer 0.5-0.6 parts; UV absorber-light stabilizer 0.25-0.35 parts; The structural formula of the flame retardant-light stabilizer is: ; The structural formula of the ultraviolet absorption-light stabilizer is: .

2. The process for preparing a prestressed structural steel strand for a wind tower according to claim 1, characterized in that: In the step I, the reaction temperature is 180°C.

3. The process for preparing a prestressed structural steel strand for a wind tower according to claim 1, characterized in that: In the step I, the reaction time is 24 hours.

4. The process for preparing a prestressed structural steel strand for a wind tower according to claim 1, characterized in that: The coating oil in step S1 further comprises 150-300 wt% of the amount of the composite lubricant in the coating oil.

5. The process for preparing a prestressed structural steel strand for a wind tower according to claim 4, characterized in that: The amount of the thiophosphate butyl octyl zinc salt is 200wt% of the amount of the composite lubricant.

6. The process for preparing a prestressed structural steel strand for a wind tower according to claim 1, characterized in that: The flame retardant-light stabilizer in step S2 is prepared by the following method: Cyanuric chloride, N-butyl-2,2,6,6-tetramethyl-4-piperidinamine and sodium hydroxide are mixed and reacted, followed by extraction to obtain an organic phase, which is dried. A hydrogen peroxide solution is added to the resultant, and after the reaction, a solid is filtered to obtain a solid, which is dried. Tert-butyl hydroperoxide and cyclohexane are added to the resultant, and after the reaction, the solid is filtered to remove the solid, and an organic phase is extracted to obtain a solid, which is dried. The purified resultant is then blended with N,N'-bis(3-aminopropyl)ethylenediamine, and after the reaction is carried out under the protection of an inert gas, the mixture is cooled, and the organic phase is separated to obtain a flame retardant-light stabilizer.

7. The process for preparing a prestressed structural steel strand for a wind tower according to claim 1, characterized in that: The ultraviolet absorption-light stabilizer in step S2 is prepared by the following method: Cyanuric chloride, N-butyl-2,2,6,6-tetramethyl-4-piperidinamine and sodium hydroxide are mixed and reacted, and then an organic phase is extracted and dried. A hydrogen peroxide solution is added to the resultant, and after the reaction, a solid is filtered and dried. Hydroquinone is added to the resultant, and after the reaction, an azeotrope is recovered, and a solid is filtered and washed and dried. The resultant is then mixed and reacted with chloroacetyl chloride, and an organic phase is extracted. The solvent is removed and the resultant is purified. Finally, the purified resultant is mixed and reacted with tetramethylpiperidinol and tetrabutylammonium bromide, and the organic phase is separated. The solvent is removed and the resultant is purified to obtain an ultraviolet absorber-light stabilizer.

8. The process for preparing a prestressed structural steel strand for a wind tower according to claim 1, characterized in that: In step S2, the raw materials used for the sheath include the following components in parts by weight: 68 parts of ordinary polyethylene; 32 parts of high-density polyethylene; 7.5 parts of toughening agent; 2.5 parts of lubricant; 0.525 parts of flame retardant-light stabilizer; and 0.315 parts of ultraviolet absorption-light stabilizer.

9. A prestressed structural steel strand for a wind tower produced by the production process according to any one of claims 1 to 8.

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