▎ 摘　　要

NOVELTY - Preparing filler, comprises (i) performing surface pretreatment of filler, (ii) performing electrochemical purification treatment on the filler, (iii) ultrasonically stripping, (iv) repeating steps (ii) and (iii) for many times, (v) electrochemical grafting of double bond-rich sulfonyl groups, and (vi) post-processing. USE - The filler is useful in coatings, preferably aqueous two-component polyurethane coating (all claimed). ADVANTAGE - The filler: has high water solubility; realizes chemical bonding between rich double bonds on its surface with other polymers, which increases the crosslinking density; and improves the physical and chemical properties of the polyurethane coating, and improves corrosion resistance of the coating. DETAILED DESCRIPTION - Preparing filler, comprises (i) performing surface pretreatment of filler, (ii) performing electrochemical purification treatment on the filler, (iii) ultrasonically stripping, (iv) repeating steps (ii) and (iii) for many times, (v) electrochemical grafting of double bond-rich sulfonyl groups, and (vi) post-processing; where the filler is graphene, and the surface pretreatment process includes placing 300-400 mg commercially available graphene powder in mixed solution of sulfuric acid and nitric acid containing three-necked flask, refluxing at 100 ℃ for 3-4 hours, naturally cooling, and filtering and washing to pH of 5-6 to obtain graphite suspension; the electrochemical purification process includes placing the graphene suspension in anode chamber of diaphragm containing electrolytic cell and stirring, and using platinum sheet as anode, and carbon rod as cathode to performing constant voltage or constant current electrochemical purification treatment, where the constant voltage electrochemical purification treatment is carried out with 1.5-3 V constant voltage for 15-17 minutes, or the constant current electrochemical purification treatment is carried out by applying constant current of 0.5-2 mA at 30-35 ℃ for 17-19 minutes, and the stirring speed is 800-900 revolutions per minute; the ultrasonic stripping process includes turning off power supply of electrolyzer, turning on ultrasonic breaker, placing ultrasonic vibrating rod of the ultrasonic breaker in the anode chamber, and ultrasonicating with the frequency of 5000-6000 Hz for 1-2 minutes; the number of repetitions in step (iv) is 5-8 times to obtain purified graphene suspension; the electrochemical grafting of double bond-rich sulfonyl groups process includes dissolving 1-2 mmol 4-methylbenzenesulfonylhydrazide in methanol solvent, then adding 10-13 wt.% tetrabutylammonium iodide, 5-10 ml saturated ammonium carbonate solution, and 7-10 g purified graphene suspension, using potassium hydroxide solution to adjusting the pH to be 8-9, and performing electrochemical reaction with the current of 40-50 mA at 25-30 ℃ for 4-5 hours; and the post-processing includes fully reacting, filtering and alternately washing with ethanol and acetone repeatedly, and ultrasonically dispersing the filtrate in surfactant containing deionized water to obtain filler suspension.