A process comprises (i) providing an isocyanate component A that is a reaction product of an aliphatic polyisocyanate, an aromatic polyisocyanate, an aliphatic polyester polyol, and a polyether polyol; (ii) providing a polyol component B comprising an aliphatic polyester polyol and a polyether polyol; (iii) mixing A and B to form a solventless adhesive (SLA) composition component A and component B each comprises an aliphatic polyester polyol having a viscosity from 800 to 6000 mPa·s at 25° C. and a hydroxyl number from 60 to 180 mg KOH/g; the SLA composition has (a) an initial viscosity at 40° C. from 500 to 1600 mPa·s, (b) an increasing viscosity ratio from 100% to 112% of the initial viscosity after the SLA composition stands at 40° C. for 10 min, and (c) an end viscosity at 40° C. from 120% to 210% of the initial viscosity at 40 min after forming the SLA composition.