Browsing by Author "Huhtala, Kimmo"

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  • The effect of binder system on coating color performance and coating structure
    (2010) Sorsa, Perttu
     School of Chemical Engineering | Master's thesis
    Binder system has more visible impact on the coating color performance than the coating structure of a double coated fine paper. In this study, the effect of different binder systems on the coating color performance were examined using several approaches, including static and dynamic water retention, viscosity, thixotropy and immobilization measurements. Binder variables used in the study were binder level, type of a binder, particle size and particle size distribution (PSD) of a binder. The structure of a dry coating layer was characterized by means of e.g. optical and physical properties of a coated paper, mercury porosimetry and SF0 printing. Both laboratory scale and pilot scale studies were pursued and the results were compared to each other. A novel concept of the binder reduction was employed. Modified styrene-acrylate (SA) emulsions were used to replace a specific amount of styrene-butadiene (SB) latex, aiming at improved coating color performance and SFO printability of a double coated fine paper at reduced binder level. Both monomodal and bimodal binder systems were examined. Binder system was noted to change the rheology and water retention of a coating color. High-shear viscosity decreased with smaller-sized particles and broad PSD of bimodal binder, and the blade loadings were slightly reduced with the decreasing viscosity. Bimodal coating colours showed improved colloidal stability but increased immobilization times. The immobilization times increased when the total binder level and proportional amount of SA emulsion increases. Small latex particle size and PSD does not increase the immobilization time to a large extent. The immobilization times of the pilot scale coating colours were higher but there was correlation to the laboratory scale coating colours. Immobilization times can be used to estimate the formation of the pore sizes. Increased immobilization time seemed to reduce the pore size. Larger pores and higher specific surface area of a binder increased the picking strength of a coating to some extent. Print gloss and optical properties did not change when the binder system was changed. Bimodal coating with 6 parts of SB latex and 2 parts of SA emulsion gave similar picking strengths with increased porosity as compared to 10 parts of reference SB latex coating. Smaller-sized bimodal binder slowed down the ink-setting rate but provided a similar print density at lower ink amount. Monomodal SA emulsion at 4 parts showed poor picking strength and low print quality, and is not suitable for SFO printing. The binder properties did not explain the changes in the immobilization time as accurately as the rheology and water retention measurements employed within the study. Changes in the formation of the pore size can be explained through the binder properties.
  • Tietojenkäsittelyn kokonaistutkimuksen kehittämistarpeiden kartoitus ja analyysi
    (1989) Huhtala, Kimmo
     School of Business | Master's thesis