Preparation method of BOPP film stiffening agent

A preparation method of a BOPP film stiffening agent, comprising:

• step (1) mixing cyclopentadiene or a derivative thereof with a norbornene monomer or C8 cycloolefin uniformly according to a mass ratio of 1:(0.1-0.5) as a polymerization raw material, and then adding polyether polyol with 0.05-5.0% of a total material mass;
• and first, putting a reaction solvent accounting for 30-60% of the total material mass into a first stirred high-pressure reactor (R101), performing a polymerization reaction at 220-250° C. for 10-20 h, and then performing the polymerization reaction in a second stirred high-pressure reactor (R102) at 240-270° C. for 10-20 h to obtain a polymerization liquid;
• step (2) removing unreacted raw materials from the polymerization liquid obtained in step (1) in a first flash tank (V101) at a pressure of 0.07-0.08 MPa and a temperature of 70-75° C.;
• after passing through an adsorption packing tower (T201), mixing the materials with a supplementary solvent and transporting to a loop hydrogenation reactor (R201);
• and subjecting the materials to a reaction with H2 at 140-180° C. under an action of a powder nickel-supported catalyst with a liquid hourly space velocity of 0.3-0.5 h−1, and obtaining a mixture of a hydrogenation resin liquid A and a catalyst;
• step (3) throwing the mixture obtained in step (2) into a filter (F201), separating the powder nickel-supported catalyst from a bottom, transporting a material at a top to a packing tower (T202), and after adsorbing and removing impurities, throwing the materials into a hydrogenation reactor (R202), subjecting the same to a reaction with H2 at 190-240° C. under an action of a Ni—Mo/γ-Al2O3 catalyst with a liquid hourly space velocity of 2-5 h−1, and obtaining a hydrogenation resin liquid B;
• and mixing the removed powder nickel-supported catalyst with the supplementary solvent, and then heating to 130-160° C. by a heat exchanger (E201) before returning to the loop hydrogenation reactor (R201);
• step (4) transporting the hydrogenation resin liquid B obtained in step (3) to a second flash tank (V301), removing a solvent at a vacuum degree of −0.085 MPa to −0.095 MPa and a temperature of 200-250° C., transporting a hydrogenation resin liquid C obtained at a bottom to a distillation tower (T301), removing low-boiling-point light components and residual solvents by distillation at the vacuum degree of −0.085 MPa to −0.095 MPa and the temperature of 200-250° C., and obtaining high-softening-point aliphatic hydrogenation petroleum resin at a tower bottom;
• and
• step (5) extruding the high-softening-point aliphatic hydrogenation petroleum resin obtained in step (4) and homo-polypropylene by a twin-screw extruder according to a mass ratio of 1:1, at the same time, adding an antioxidant, and then obtaining the BOPP film stiffening agent by granulation and cooling.