Through semi-batch emulsion polymerization

hydrophobically modified associative thickener latexes were prepared using methacrylic acid and ethyl acrylate as the main monomers

behenyl polyethoxylate ether methacrylate as the functional monomer and dially phthalate (DAP) as the crosslinking agent.Ammonium persulfate was used as the initiator.Properties of the thickener latexes prepared with different amount of DAP

including viscosity

particle size and size distribution

were determined.Evolutions of the viscosity and light transmittance with increasing pH in the thickener latexes were followed.With pH starting from 6.0

light transmittance of the thickener latexes sharply increased

reached a maximal value at pH around 8.1

it remained relatively constant with continuing pH increase.As to the viscosity

a significant increase was also observed at the same time with the light transmittance

followed by a slow decline afterwards.It was found that the properties of the thickener latexes were closely related to the DAP amount used in their preparation.Thickening performance and shearing resistance of the associative thickeners were enhanced when thickener polymers were slightly crosslinked with a low amount of DAP;A too large amount of DAP led to deteriorated swelling and dissolution for the latex particles under alkaline condition

reducing therefore the thickening performance of the thickener.The results were fully interpreted and the thickening mechanism was discussed.