Date of Award
Bachelor of Science
Paper Science and Engineering
In recent years there has been a growing demand for the use of synthetic latexes as sole binders in coating formulations. This had been brought about by the shortage of supply and changing prices of natural binders like casein and protein. Synthetic latex binders require no cooking; this increased energy saving over starch becomes more important as fuel prices rise. Synthetic latex systems are easy to handle and they can be combined easily to fit different requirements.
Most synthetic latex systems need a thickener and water retention aid to achieve the right viscosity and flow properties. The new alkali-swellable latexes will produce a thickening effect upon alkali addition. These latexes are alleged to have better water retention and binder control than the other non-reactive latex binders.
Water retention is a direct indicator of binder migration in a coating application, since some latex binder travels with the water into the paper substrate. Water retention determines leveling of the coating after application. The hold-out qualities of the dried coating and the rate of drying are also affected by water retention. Physical and optical properties will vary with changing water retention of the coating color. It is generally accepted that water retention is dependent on viscosity and solids content.
This study examines alkali-swellable latex systems to determine how pH levels of the coating color can affect physical and optical properties of the coated paper. AN all alkali-swellable system and an alkali-swellable standard unreactive latex system was applied to a groundwood stock at varying pH levels. Coat weight and percent solids were held constant, and coated samples were tested for any physical or optical changes. Viscosities were measured at the different coating color pH levels using high and low shear equipment.
Justen, Larry N., "The Effects of pH on Alkali-Swellable Latex Binder Coating Systems" (1976). Paper Engineering Senior Theses. 232.