Features of the coagulating and peptizing action of weakly basic and strongly basic cationic polyelectrolytes on rosin emulsions

Abstract

It has been shown for the first time that cationic polyelectrolytes (weakly basic (polyamide-polyamine-epichlorohydrin resin (PPER)) and strongly basic (polydimethyldiallylammonium chloride (PDMDAAC) and copolymer of acrylamide with methylene chloride dimethylamminopropylacrylamide (CA MC DMAPA)), widely used in paper and cardboard technology as flocculants (existing technology), additionally participate in the processes of coagulation and peptization (proposed technology). It has been established that the coagulating ability of polyelectrolytes decreases in the series CA MC DMAPA > PDMDAAC > PPER, while the peptizing ability, on the contrary, increases. Peptizable coagulants with the size and ξ-potential that do not exceed 5200 nm and +15 mV, respectively, are formed in the presence of PPER, when its content in the dispersed system does not exceed 0.15 parts by weight / parts by weight of the dispersed phase of the rosin emulsion (RE). The first region of electrolytic coagulation RE (proposed technology) corresponds to the ratio of RE : electrolyte in the range from 1: 0.3 to 1: 0.6, while with an increased content of electrolyte in the dispersed system (existing technology), which is in the range of 1: 2.4 to 1: 3.0 , the coagulation process proceeds in the second region (the resulting coagulates are electrically neutral and coarse (size exceeds 5200 nm) and are not able to peptize). The peptization process proceeds in the dispersed system “RE (1.0 wt. parts) – PPER (0.04 wt. parts) – electrolyte (0.6 wt. parts)”. The presence of PPER promotes an increase in the ξ-potential of peptized particles from +35 to +50 mV. Unlike coagulates, such particles provide a shift in the sizing process from the traditional mode of homocoagulation to a more efficient mode of heteroadagulation. This results in an increase in the hydrophobicity and strength of paper (cardboard) by 29–36 and 28–38 %, respectively, as well as in an improvement in the printing properties of coated products by 12–15 %.