Preparation method of high-performance star-shaped polycarboxylate superplasticizer

A preparation method of a star-shaped polycarboxylate superplasticizer, comprising an esterification step and a polymerization step in sequence, wherein:

• (1) the esterification step:
• polyol is added to a reactor and heated to a temperature of 40-80° C., and then a polymerization inhibitor, (meth)acrylic acid and catalyst are added to the reactor in turns with each interval of 5-20 minutes and constant stirring, heating is continued and a water-carrying agent is added when the temperature reaches 80-100° C., after continual heating to 100-150° C., esterification is carried out and, during the esterification, produced water is separated, after reaction for 2-10 hours, the water-carrying agent was removed by vacuum pumping, and an esterification product is obtained;
• (2) the polymerization step:
• the esterification product and water are added to the reactor and heated to a temperature of 50-65° C. and stirred for 10-30 minutes, and then unsaturated polyoxyethylene ether, molecular weight regulator, (meth)acrylic acid or its mixture with unsaturated carboxylic acids, and a persulfate solution with a mass concentration of 1-30% as initiator are added to the reactor in turns with each interval of 5-20 minutes and constant stirring, after continual heating to 65-90° C., polymerization is carried out, after reaction for 1.5-8 hours, the temperature is lowered to 40-60° C. and the product is neutralized by an alkaline solution with a mass concentration of 10-50% to adjust pH value to 6-8, after cooling to a temperature of 25-40° C., a solution of the star-shaped polycarboxylate superplasticizer with a desired concentration is finally obtained by mixing appropriate amount of water;
• wherein in step (1), the polyol used in the esterification is glycerol, trimethylol ethane, trimethylol propane, pentaerythritol, xylitol, mannitol or sorbitol;
• the inhibitor used in the esterification is hydroquinone, phenothiazine, p-tert-butylcatechol or hydroquinone monomethyl ether, with the mass dosage of 0.05-5% of the (meth)acrylic acid;
• the catalyst used in the esterification is p-toluenesulfonic acid, phosphoric acid or sulfamic acid, with the mass dosage of 1.5-10% of all the reactants;
• the water-carrying agent used in the esterification is cyclohexane, benzene or toluene, with the mass dosage of 8-30% of all the reactants, and the reactants are the polyol and (meth)acrylic acid;
• in step (2), the mass of added water is 80-120% of the mass of the unsaturated polyoxyethylene ether and (meth)acrylic acid or its mixture with unsaturated carboxylic acids;
• the unsaturated polyoxyethylene ether is allyl polyethylene glycol, methyl alkenyl polyethylene glycol, isobutenyl polyethylene glycol or isopentenyl polyethylene glycol;
• the molecular weight regulator is mercaptoacetic acid, mercaptopropionic acid, sodium methallyl sulfonate, sodium allyl sulfonate or n-dodecyl mercaptan, with the molar ratio of 0.05-0.75:1 to the unsaturated polyoxyethylene ether;
• the unsaturated carboxylic acids are one or several of itaconic acid, maleic acid (anhydride) and fumaric acid, with the molar ratio of 0.1-5:1 to (meth)acrylic acid mentioned in step (2);
• the persulfate initiator is ammonium persulfate, potassium persulfate or sodium persulfate, with the molar ratio of 0.05-0.5:1 to the unsaturated polyoxyethylene ether;
• the solute of the alkaline solution is sodium hydroxide, potassium hydroxide, ethylenediamine or triethanolamine, with the molar ratio of 0.7-1.2:1 to the (meth)acrylic acid or its mixture with unsaturated carboxylic acids mentioned in step (2).