Abstract:

Waterborne polyurethane （WPU） hybrid emulsions were prepared from polycaprolactone glycol （PCL）, tolylene diisocyanate （TDI） and dimethylolpropionic acid （DMPA）, with trimethylol-propane （TMP） as the crosslinking agent and with epoxy resin and rosin as the modification agents. The structures and properties of the products were then characterized by means of FTIR, particle size analysis, GPC and DSC. The results indicate that the preparation of WPU is due to the formation of urethane groups via the reaction between the hydroxyls in epoxy resin and the diisocyanate groups in TDI, to the ring-opening reaction, and to the participation of grafting of epoxy resin onto the polyurethane （PU） molecules via a ring-opening reaction, and to the participation of carboxyls in rosin in the reaction. Moreover, it is found that the average particle size of WPU hybrid emulsions increases with the contents of epoxy resin and rosin, that the relative molecular mass of the modified WPU is up to 7.43 × 10⁵ , that the content of TMP should not be more than 2. 7% due to its great effect on the peeling strength of WPU film, that epoxy resin, PU and rosin all have good compatibil- ity after the modification, and that the decomposition temperature of the cast films is more than 260 ℃, revealing strong adhesion strength of the adhesive formulated by the modified WPU emulsion for various laminated package films.

Key words: waterborne polyurethane, epoxy resin, rosin, hybrid emulsion, synthesis, modification