Addition of polyvinylamine in chemi-thermomechanical pulp and kraft pulp and the effects on dewatering, strength, and air permeance

Abstract

The addition of polyvinylamine (PVAm) in the wet-end of the papermaking process was investigated. The changes in pulp drainage, vacuum dewatering, tensile strength, and air permeance were measured with and without PVAm. Both chemi-thermomechanical pulp (CTMP) and bleached kraft pulp were used. The dewatering and drainage abilities of the different pulps was examined by measuring the dewatering resistance (°SR), the water retention value (g/g), and the vacuum dewatering. The tensile strength and air permeance values were tested on paper sheets. The results showed that the initial dewatering was faster for pulps with PVAm, and this effect was greater for the CTMP and at higher basis weights. The strength increased when PVAm was added but only if the pulp was washed before sheet forming. The unwashed pulp with PVAm had worse formation, which resulted in lower tensile strength values. The air permeance of the sheets was higher with the addition of PVAm, primarily as a result of higher flocculation. Adding PVAm to the stock suspension in the wet-end of the paper machine has great potential for end-products that require high air permeance and tensile strength properties. PVAm could also act as a dewatering enhancing agent, but caution must be taken regarding the potential of formation problems.

Method for studying water removal and air penetration during through air drying of tissue in laboratory scale

“…5. The typical shape of the diminishing returns of the dewatering curve is consistent with both previous data from the same laboratory equipment (Sjöstrand et al 2016(Sjöstrand et al , 2017(Sjöstrand et al , 2019Rahman et al 2018;Sjöstrand and Brolinson 2022), and with laboratory and pilot data from other publications of vacuum dewatering (Attwood 1962;Neun 1994Neun , 1996Räisänen et al 1996;Ramaswamy 2003;Pujara et al 2008). The shape of the dewatering curve shows the well-known dewatering mechanism for vacuum dewatering where water between the fibers is removed first, to an initial high dewatering rate, and as the water becomes increasingly less accessible the dewatering rate levels out, and gradually goes to zero.…”

Enhancing Through Air Drying process efficiency: Investigating laboratory-to-pilot scale correspondence and impact of process variables on tissue paper manufacturing

“…The air volumes are directly connected to the pump energy in the vacuum section and thus connected to energy consumption of the process (Sjöstrand 2023). The dewatering behavior for the forming fabric was expected and in line with previous observations of vacuum dewatering and penetrated air volume (Attwood 1962;Neun 1994Neun , 1996Räisänen et al 1996;Ramaswamy 2003;Pujara et al 2008;Sjöstrand et al 2016Sjöstrand et al , 2017Rahman et al 2018;Sjöstrand and Brolinson 2022;Sjöstrand et al 2023;Sjöstrand 2023). According to the laboratory results of solids content development for TAD fabrics (Fig.…”

Improved vacuum dewatering of grease-proof paper utilizing a multi-slit vacuum suction box in laboratory scale

“…These asymptotes would thereby be overcome by utilizing a higher degree of vacuum by the time these asymptotes have been reached in order to reach a higher degree of dryness, with a lesser energy expenditure (Attwood 1962;Neun 1994;Räisänen et al 1996;Baldwin 1997;Räisänen 2000;Ramaswamy 2003;Granevald et al 2004;Pujara et al 2008;Rahman et al 2018;Sjöstrand et al 2019Sjöstrand et al , 2023Hubbe et al 2020;Sjöstrand and Brolinson 2022). Common commercial paper machines utilize dwell times in terms of milliseconds (Ramaswamy 2003).…”