Filler Retention Research Articles

Paper Making Furnish as a Composite Blend. Some Wet End Interactions among Furnish Ingredients

ABSTRACTC.A. Hogart defined paper as “a random bonded fibrous network carrying filler material“. A few thoughts related to this definition and pertaining to paper composites are presented.A typical papermaking furnish consists of a blend of cellulosic fibers and fines, inorganic fillers and additives. Composition varies according to end use requirements. The fiber network secures desired mechanical and strength properties, fillers contribute to esthetics and good optics. Filler retention is improved by using retention aids. Strength-loss due to filler, use is compensated for, by applying strength additives.Additives applied at the wet end interact with furnish components. The surface charge, accessible surface area and composition play a role in the interactions. Some typical interactions, involving cationic starch and polyacrylamide, are discussed.

Polyacrylamide as a filler retention aid for bagasse paper pulp

AbstractThe polyacrylamide (PAM) produced as a homopolymer byproduct during the grafting of cellulose by acrylamide was partially hydrolysed for 2 and 4 hours. The three prepared polymers besides Accostrength® 86, which is mainly a dry strength resin and also improves retention of fillers and fines, were used as filler retention aids for bleached bagasse. Three fillers were used, namely titanium dioxide, silica and kaolin. The results obtained showed that the PAM hydrolysed for 2 hours gave the best results for both filler retention and improvement of strength properties. The values obtained for this polymer were comparable with those obtained for the commercial polymer.

Effect of aluminium sulphate on the retention of inorganic fillers

AbstractThe effect of aluminium sulphate on the retention of inorganic fillers during the process of papermaking has been investigated. It is found that increased filler retention is achieved mainly in the pH range 4–9, this increase being attributed to the fact that adsorption of charged aluminium species occurs in this pH range giving rise to a decrease in mobility, and hence ζ potential, of the fibres and a reversal of ζ potential of the filler particles. The filter is then retained by heteroflocculation of the fibres with the filler particles.

Cationic and Nonionic Starch Graft Polymers for Filler Retention

AbstractGraft co‐ and terpolymers were prepared by free radical polymerizations of vinyl monomers onto ω‐irradiated starch by a prototype commercial process. Products with graft contents of up to 46%, by weight, were obtained by grafting acrylamide and quaternary amine‐containing esters of methacrylic acid to starch. The graft polymers were evaluated on a pilot fourdrinier paper machine as filler retention aids and compared with several commercial flocculants. Drainage rate increased markedly with one of the starch graft terpolymers that was cationic. Since the number of starch graft polymers prepared was limited, the results reported, although excellent, are not necessarily optimal. Further studies are needed to establish the relationships of graft content and terpolymer compositions to retention and drainage.

Studies on the Papermaking by Use of Surface Sizing Techniques (II)

If alum is cut back or removed from the wet end, retention of fines and filler in the sheet is generally reduced, which may result in poor formation of the sheet. Thus, in this paper was discussed the filler retention in producing base sheet for surface sizing by both laboratory applications and field pilot scale trials.Calcium carbonate (both ground limestone and precipitated calcium carbonate) was compared with the hitherto generally use clay and with other fillers. In particular, it was thought that ground limestone would be a very advantageous filler, because it had superior optical property and very low abrasiveness, and could be obtained at a low price. Thus, it was evaluated to determine whether it would be useful at filler for base sheet for surface sizing.As a result, it was found that ground limestone of a small particle size (for example, 1.8μ) improved the opacity (scattering coefficient) of the sheets. The use of filler retention aids proved more effectively with the ground limestone than with the precipitated calcium carbonate. The ground limestone was retained up to 80% by adding 0.010.02% cationic or anionic synthetic polymer based on filler weight as a retention aid continuously to the riffler just prior to the headbox. What is more, this was a sheet having a higher optical property and greater strength property as compared with the sheet of a clay/rosin/alum system. It was known that when ground limestone filled sheet was surface-sized at size press, it could be made into a sized paper having a remarkable sizing response just as in the case of precipitated calcium carbonate.Ground limestone filled paper has the following advantages;(1) Ground limestone itself is a lower-priced filler.(2) It has a better optical property and a very low abrasiveness than clay.(3) It has a superior strength property as compared with the sized paper of a clay/rosin/alum system. Thus, more of the expensive pulp weight has been replaced by the low-cost filler.

Electron Microscopic Studies of Surface Fine Structure of Papers

Electron microscopic studies were carried out with regard to the effects of the filling, the internal sizing and the surface sizing on the surface fine structures of uncoated papers. Results were summerized as follows : (1) Direct carbon reprica technique was found to be available especially for observing filler distribution on uocoated paper surfaces. (2) By observing commercial uncoated paper surfaces by the transmission and scanning electron microscopy, it was found that the wire side showed a greater filler loss than the top side. (3) The two sideness of filler retention was found to depend on the methods of sheet formation. In hand made sheet, the wire side had higher filler retention than the top side. On the paper made by the miniature fourdrinier paper machine, the two sideness of filler retention was almost eliminated. On the paper made by the commercial fourdrinier paper machine, the filler retention of the wire side was conspicuously lower than the top side. (4) Two sideness of the filler retention of commercial papers was found to be increased as the filler content increased. (5) In the surface sizing, surface of the fibers were found to be covered with an amorphous film of a sizing agent in proportion to the degree of sizing.