• 펄프종이기술
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• 제47권2호
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• pp.53-60
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• 2015

The effects of stirring speed during filler modification by dual polymers on flocculation and reflocculation of PCC (precipitated calcium carbonate) particles and its effect on handsheet properties were elucidated. PCC surface was modified by adsorbing A-PAM (anionic polyacrylamide) and C-starch (cationic starch) in series at various stirring speeds. It was found that increasing stirring speed during filler modification decreased the initial floc size of PCC. Continuous stirring with the same speed for filler modification resulted in the decrease of a floc size, eventually reached a steady state. The variations in a floc size was influenced by the stirring speed during filler modification: the lower the stirring speed during filler modification, the larger the floc size variations. Conclusively, the stability of PCC floc could be improved by increasing the stirring speed. In addition, the stirring speed influenced the handsheet properties. The smaller the PCC floc, the lower the strength of handseet. However, too much larger floc size also deteriorated paper strength. There exists an optimum floc size in term of paper strength which shall be controlled by stirring speed during filler modification.

• 펄프종이기술
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• 제43권3호
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• pp.35-42
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• 2011

In this study, ground calcium carbonate (GCC) was modified by Layer-by-Layer (LbL) multilayering with polyelectrolytes. Cationic polyacrylamide (C-PAM) and poly sodium 4-styrene sulfonate (PSS) were used as cationic and anionic polyelectrolytes to modify GCC. The characteristics of the modified GCC were examined in terms of zeta potential and particle size with the addition level of polyelectrolyte and layer number. The GCC could form an assembly of cationic and anionic polyelectrolytes through consecutive adsorption process. The zeta potential of the modified GCC moved toward the cationicity and reached the plateau with the increase of the addition level of C-PAM. With layering of anionic PSS, the GCC had the negative charge. The particle size was dependent on the zeta potential. It was also observed by optical microscope. As the PSS was in the presence of the outermost layer, the GCC showed the better dispersability. It indicated that the surface charge and particle size can be controlled by adjusting the addition level of polyelectrolyte and the layer number.

• Geomechanics and Engineering
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• 제13권2호
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• pp.319-331
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• 2017

This vacuum preloading combined with polyacrylamide (PAM) flocculation was proposed to separating solid-liquid in waste slurry and to improving bearing capacity of soft soil ground. By using waste slurry taken from drilled shaft construction site in Shanghai, China, a series of settling column tests with four typical flocculants and one normal for waste slurry were carried out for comparative analysis. The optimal amounts for each flocculant were obtained from the column tests. Then, model tests on vacuum preloading with anionic polyacrylamide (APAM) flocculation and without flocculants were carried out. The out of water and the settlement of slurry surface ground were monitored during the model tests, and the changes in water content, particle-size and pore-size distributions in different positions after the model tests were measured and discussed. It is found that water content of the waste slurry without APAM flocculation changed from 204 to 195% by 24 hours standing and 15 hours vacuum preloading, while the water content of the waste slurry with APAM flocculation was declined from 163 to 96% by 24 hours standing, and was further reduced into 37% by 136 hours vacuum preloading, which shows that the combined method is feasible and effective.

• 펄프종이기술
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• 제46권5호
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• pp.51-60
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• 2014

To find a practical application approach of polyelectrolyte multilayering (PEM) on inorganic filler, we introduced PEM process without washing step and investigated the effect of shear condition on the washless PEM treatment of ground calcium carbonate (GCC). Washless multilayering on GCC was conducted under various shear conditions such as stirring, homogenization, and ultrasonication. Highly charged polyelectrolytes combination of polydiallyldimethylammonium chloride (PDADMAC) and poly sodium 4-styrene sulfonate (PSS) and low charged polyelectrolytes combination with cationic starch and anionic polyacrylamide (PAM) were compared. In the case of highly charged polyelectrolytes combination, shear conditions did not affect the zeta potential and the particle size of treated GCC. However, the modified GCC particles with low charged polyelectrolytes were more dispersed under higher shear condition while maintaining the zeta potential. In addition, GCC was successfully modified through laboratory inline washless polyelectrolyte multilayering system which consists of homogenizers and pumps.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.271-278
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• 2006

We used polymers of alternating cationic and anionic nature to build up shells on fiber surfaces, strengthen the worn-out fibers and improve paper properties made from such fibers. OCC and ONP pulps were either dipped or salted out in the cationic polyallylamine, polyacrylamide and starch solutions. After centrifugal drying, these were followed by treatments in anionic polyacrylic acid, poly-acrylamide, and starch solutions, respectively. The shell-enhanced fibers were formed into handsheets and their physical properties evaluated. The results show that building multiple shells on worn-out fiber surfaces can strengthen the fibers and paper. The simpler and more practical impregnation-centrifuging treatment provided the desired effects, whereas salting out the polymers produced somewhat superior fibers. The latter process, were impractical, however. The first pair of polymeric shells imparted marked strength improvement, whereas later layers had diminishing efficacies. Overall, the methods can improve fiber quality, attaining paper strength requirements without resorting to expensive measures. Alternate cationic polymer and filler powders were also deposited on fiber surface based on the micriparticle system in an anticipation of stiffness gains. Platy minerals, such as montmorillonite, bentonite, sericite, clay and talc were added following cationic PAM. After dewatering of polymer-pigment shelled fiber of one to 3 pairs of layers, handsheets either calendered or uncalendered were evaluated. The results indicate that regardless of calendaring, stiffness of the handsheets did not improve appreciably while certain other strength properties showed gains. We also attempted the novel starch gel filler addition method wherein tapioca starch and filers (PCC, sericite or clay) were mixed at high solids content of 50% and cooked until gelatinized. The filled handsheets were dried under various conditions and then tested for their properties. Improvements in strengths of modified filled paper were observed.

• Membrane and Water Treatment
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• 제7권2호
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• pp.101-113
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• 2016

In this study, to improve the water flux of porous hydrophobic membranes, various water-soluble polymers including neutral, cationic and anionic polymers were adsorbed using 'salting-out' method. The adsorbed hydrophobic membrane surfaces were characterized mainly via the measurements of contact angles and scanning electron microscopy (SEM) images. To enhance the durability of the modified membranes, the water-soluble polymers such poly(vinyl alcohol) (PVA) were crosslinked with glutaraldehyde (GA) and found to be resistant for more than 2 months in vigorously stirred water. The water flux was much more increased when the ionic polymers used as the coating materials rather than the neutral polymer and in this case, about 70% of $0.31L/m^2{\cdot}h$ (LMH) to 0.50 LMH was increased when 300 mg/L of polyacrylamide (PAAm) was used as the coating agents. Among the cationic coating polymers such as poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA), poly(acrylic acid-comaleic acid) (PAM) and poly(acrylic acid) (PAA), PSSA_MA was found to be the best in terms of contact angle and water flux. In the case of PSSA_MA, the water flux was enhanced about 80%. The low concentration of the coating solution was better to hydrophilize while the high concentration inclined to block the pores on the membrane surfaces. The best coating condition was found: (1) coating concentration 150 to 300 mg/L, (2) ionic strength 0.15, (3) coating time 20 min.