We are manufacturer of latex-based adhesives. Please give us some general guidance in blending of two different latices and the addition of fillers in terms of latex colloidal stability.
John Woon (Senior Latex Consultant):
I suggest you look into the following points:
1) Blending of two different latices (latexes)
1.1) Make sure the pH of both latices are as close as possible. By changing the latex pH, the latex could sometimes be destabilized in which case, it is advisable to add a non-ionic surfactant to that latex before the pH adjustment.
1.2) Latex with smaller particle size would tend to rob the surfactant already present on the particles of latex with higher particle size. Generally, the level of surfactants required for the blend is more than the total amount required for the two individual latex.
2) Filler addition
2.1) You could either add the filler dry or as a pre-prepared slurry to the latex. The former would require higher level of surfactant than the latter.
2.2) The higher the level of filler, the higher is the level of surfactant required.
2.3) Filler with smaller particle size would tend to rob more of the surfactant from the latex particles compared to filler with coarser particles.
2.4) Filler type is important e.g. clay and talc would have less destabilizing effect on the latex compared to calcium carbonate.
2.5) Generally a combination of surfactants performs better than a single surfactant.
Hope this helps.