Following our success with the first generation of HYBRID chemistry, we continued our efforts towards increasing the molecular weight of HYBRIDS. Large differences between the reactivity of DADMAC and acrylamide monomers – already a technical challenge for first generation lower molecular weight products – shifted our efforts towards other vinyl cationic monomers. A large amount of work was put into optimising the charge and molecular weight of polymers in terms of synthesis and performance. This work resulted in an introduction to market of the second generation of HYBRIDS. Due to the higher molecular weight and viscosity of solutions, both first and second generations are supplied in the form of oil-in-water emulsions or, in some cases, dispersions. To eliminate a need for expensive and large footprint polymer inversion equipment, the final polymer formulation that was developed offered a good balance between easy inversion and high emulsion stability. This result was significantly more complex for the second generation of HYBRIDS due to their higher molecular weight. Figure 3 represents the first and second generation of HYBRID polymers in the grid of molecular weight (RSV) and charge (mole%). TYPICAL APPLICATION STRATEGY Early Fixation: each pulp stream, with the significant loading of extractives, should be treated separately, prior to blending stage. This allows early fixation to prevent time-driven agglomeration. Selecting this first fixation point immediately after any on-machine refining stage, is highly recommended. In the case of mechanical pulps (TMP, GWD, PGW) typically equipped with large thick stock storage towers, this early treatment can be split into pre-tower and post-tower addition points. Pre- tower fixation prevents agglomeration that could potentially occur during a long storage time of untreated pulp. Figure 3. Position of HYBRID polymers in relation to typical coagulants and cationic flocculants. WORLD PULP&PAPER 95 Chemistry, size and charge differences of contaminants allowed us to question the one-size-fits- all approach to their control