Date of Award

4-1997

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

The objective of this thesis proposal is to determine the effect of a varying latex binder on the physical and optical characteristics of a coated sheet with different binder addition levels. A total of nine separate coating formulations were made up of three different styrene to butadiene ratios and three different binder addition levels. The optical properties that were tested include opacity, brightness, paper gloss, and K&N ink absorption. The adhesive properties were evaluated by testing the physical properties of pick strength, abrasion resistance, and wet rub. The porosity and roughness characteristics were also tested.

One liter of each coating formulation was made and ran on the CLC laboratory coater. A fifty pound basis weight base sheet was used. The parameters such as coat weight, percent solids, low shear viscosity, pH, pigment, and drying conditions were held constant at values to ensure good runnability on the CLC and resembling those most commonly used within the industry. The focus of this thesis topic being the binder variable, more specifically styrene-butadiene latex.

The latex was obtained from the Dow chemical company at three different styrene to butadiene ratios within each latex. One formulation contained Dow 617 latex (hard} with a styrene/butadiene ratio of 1.9 and a glass transitional temperature (Tg) of 18 C. The second formulation contained Dow 620 latex (typical) with a styrene/butadiene ratio of 1.7 and a Tg of 12 C. The final formulation contained Dow 679 latex (soft) with a styrene/butadiene ratio of 1.3 and a Tg of -10 C. The amount of latex binder based on dry pigment became another variable. One coating formulation contained the typical 12% binder, one was lower approximately containing 8% binder, and the other was above the typical at 18% binder based on dry pigment.

By altering the latex binder, the properties of the coating formulation itself alters. Certain properties such as film formation, glass transitional temperature, coalescence, and pigment to binder interactions all vary by changing the amount and type of latex. It can be concluded that the hard latex at a lower binder level is desired to achieve optimum optical characteristics while soft latex at a high binder level is desired for optimum binding strength characteristics. A compromise between the two must be achieved while making the proper coating formulation.

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