Transparent polypropylene resin and preparation method thereof

A method for preparing a transparent polypropylene resin, comprising steps of:

• A) pre-polymerizing propylene in the presence of a main catalyst, a polymeric nucleating agent, a co-catalyst, and an external electron donor;
• wherein the polymeric nucleating agent is selected from the group consisting of poly(vinylcyclopentane), poly(vinylcyclohexane), poly(vinyl-2-methylcyclohexane), poly(3-methyl-1-butene), poly(3-ethyl-1-hexene), poly(3-methyl-1-pentene), polystyrene, and a combination thereof;
• and a mass ratio of the main catalyst to the polymeric nucleating agent is 1:(1-2);
• B) subjecting the pre-polymerization product, propylene, ethylene, and hydrogen to a polymerization reaction to obtain a polypropylene powder;
• C) continuing a polymerization reaction of the polypropylene powder, propylene, ethylene, and hydrogen to obtain a polypropylene resin powder;
• D) mixing the polypropylene resin powder, an antioxidant, a halogen scavenger, an antistatic agent, and a sorbitol-based nucleating agent evenly to obtain a mixture;
• wherein the sorbitol-based nucleating agent is 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol;
• and a mass ratio of the polymeric nucleating agent to the sorbitol-based nucleating agent is 1:(75-150);
• and
• E) extruding the mixture through an extruder to obtain a transparent polypropylene material;
• wherein a temperature of the highest temperature zone of the extruder is 230° C. to 240° C.