Synthesis Of Rosin Modified Polyether Glycol And Its Application In Polyurethane Coatings

Polyurethane is one of the most popular type of coatings,which have been wildly used because of its controllable molecule structure and excellent comprehensive properties.Rosin is an abundant forestry resource in China with a yield of more than 1.4 million tons.However,the utilization of rosin resources in China is still at a relatively primary stage and lack of high value-added products at present.In the past few years researches of rosin-based polyurethane,the Diels-Alder reaction of rosin and acrylic acid / fumaric acid / maleic anhydride was regularly used to obtain dicarboxylic acid,and then polyol was prepared by esterification.This method takes a long-time and high temperature reaction to convert rosin into polyester polyol which can be used in polyurethane.The mechanical properties of polyurethane foam producing by this kind of rosin modified polyester polyol were fine due to the phenanthrene ring of rosin,which is located at the main chain of polymer,but were usually too brittle when in coatings application.In this paper,rosin-modified polyether glycol(RPG)was obtained vis solvent-free one-step reaction of rosin and poly(propylene glycol)diglycidyl ether in 120°C with triethylamine as catalyst.That makes it easier to realize industrialization for reducing the energy consumption of production,saving the utilization cost of rosin by simplifying the step of synthesis of hydroxyl resin from rosin to polyurethane.Furthermore,three kinds of polyurethane coatings were prepared by using RPG.(1)High-solid content two-component polyurethane coatings were prepared,the effects of R value(NCO/OH),curing agent type,catalyst type and amount of catalyst on coating performance were studied.With the optimal formula,the pendulum hardness reached 0.61 and the 60 °gloss reached 133,the adhesion was 1 grade,the impact roughness was 50 kg·cm,the flexibility reached 1 mm,and the water resistance was more than 30 days.(2)Rosin-based waterborne polyurethane dispersion was prepared with RPG as soft segment.The effect of R value,reaction time and soft segment content on film properties were studied,the addition of bis(hydroxymethyl propionic acid)and trimethylolpropane(TMP)were considered as well.With the optimum formula,the pendulum hardness reached 0.66,the 60 °gloss reached 142.9,the adhesion reached 1 grade,the flexibility reached 1 mm,and the impact roughness reached 50 kg·cm,the water resistance was more than 72 hours.(3)UV-curable rosin modified polyurethane resin was synthesized by reacting RPG with hexamethylene diisocyanate and then capping with hydroxyl acrylate monomer.The effects of different end-capping monomers,active diluents and their dosages,crosslinked monomers and their dosages,amounts of adhesion-promoting monomers,photoinitiators and curing time on the film properties were studied.With the optimal formula,the pendulum hardness reached 0.63 and the 60 °gloss reached 153.9,the adhesion was second grade,the impact roughness was 50/45 kg·cm,the flexibility reached 1 mm,and the water resistance was more than 30 days.