Papermaking Additives Research Articles

Advanced nano-based manipulations of molasses in the cellulose and paper discipline: Introducing a master cheap environmentally safe retention aid and strength promoter in papermaking

This work introduces, for the first time worldwide, molasses – a byproduct of the sugar industry – as a master retention aid and strength promoter in papermaking. The paper nanocomposites produced in the present work – involving molasses, natural cellulose fibers, and kaolin – retained larger amounts of kaolin while exhibiting greater strength, as compared to their molasses-free counterparts. Recently, the authors have shown, for the first time, that the nanoadditive sucrose can overcome the ultimate fate of deterioration in strength of paper, due to addition of inorganic fillers such as kaolin. This deterioration was counteracted by incorporating the nanoporous structure of cellulose fibers with sucrose, which leads to incorporation beating of the fibers, and thus increases the strength of the produced paper nanocomposites. In addition, the nanoadditive sucrose was proven – for the first time – to act as retention aid for inorganic fillers such as kaolin. We called this phenomenon incorporation retention to differentiate it from the conventional types of retention of inorganic fillers. On the other hand, it is well established in the literature that using gums (including starch) as additives in papermaking enhances the strength of paper. Molasses contains both the nanoadditive (sucrose), and gums (including starch). Molasses is a byproduct of sugar industry, which is cheaper than sucrose; and a major part of sucrose lost in sugar industry resides in molasses. Moreover, molasses is an environmentally safe additive. Therefore, the nanoadditive (molasses) was chosen, in the present work, to be manipulated as a master strength promoting retention aid for inorganic fillers used in papermaking, such as kaolin.

Preparation of Cellobiose-conjugated Polyacrylamide and its Interaction with a Cellulose Matrix for Papermaking Application

Cellobiose, a structural subunit of cellulose, was utilized as a retention promoter of polymer additives to a cellulose matrix in an aqueous papermaking system. beta-D-Cellobiosylamine was conjugated with anionic polyacrylamide (A-PAM) through a condensation reaction using water-soluble carbodiimide. Glyco-modified A-PAM containing cellobiose residues (CB-A-PAM), which was added to a pulp suspension using tap water, had good retention efficiency and enhanced the strength of paper sheets. Surface plasmon resonance analysis gave useful information on the affinity of CB-A-PAM for a cellulose matrix. Cellobiose and A-PAM had negligible interaction with cellulose, but CB-A-PAM was significantly adsorbed on the cellulose surface. It was presumed that the many cellobiose moieties in one CB-APAM molecule cooperatively enhanced its affinity for cellulose. Such sugar−sugar interaction is a novel concept for the retention system of papermaking additives and the functional design of carbohydrate-based materials.

Influence of hemicellulosic derivatives on the sulfate kraft pulp strength

In this work the application of different hemicellulosic derivatives including different degrees of substitution (DS) cationic hemicelluloses and carboxymethyl hemicelluloses in sulfate kraft pulp were investigated in detail. It was found that cationic hemicelluloses and carboxymethyl hemicelluloses could improve the physical properties of hand sheets, while the cooperation of cationic hemicelluloses and carboxymethyl hemicelluloses could enhance sharply the physical properties of hand sheets. When the dosages of cationic hemicelluloses with DS of 0.37 and carboxymethyl hemicelluloses with DS of 0.35 were 1.0% and 1.0% (based on dry pulp weight), respectively, the physical properties of hand sheets was significantly improved, breaking lengthen and tear index of hand sheets increased by 21.1% and 54.6% compared with the control hand sheets without any additives added. The fiber intertexture of the hand sheets was observed by SEM. The results indicated that hemicelluloses could be used as the source for the production of wet-end additives in papermaking, which might represent an important strategy for sustainable use of the agricultural residue.

Specific interaction acting at a cellulose-binding domain/cellulose interface for papermaking application

Specific and strong cellulose-binding characteristics were utilized for promoting retention of additives in contaminated papermaking systems. Cellulose-binding domain (CBD) of cellulase derived from Trichoderma viride was separated by digestion with papain, and then introduced into anionic polyacrylamide (A-PAM) through a condensation reaction using water-soluble carbodiimide. The CBD-modified A-PAM (CBD-A-PAM) showed good retention on pulp fibers, resulting in high tensile strength paper sheets. The effect remained almost unchanged in the presence of model interfering substances such as ligninsulfonate and Ca2+ ions, whereas commercial cationic paper-strengthening polymer became ineffective. The cellulose-binding force of CBD was quantitatively determined by atomic force microscopy (AFM) in the liquid state. Histidine-tagged CBD protein was obtained using Escherichia coli via an expression of CBD derived from Cellulomonas fimi, and immobilized on a gold-coated AFM probe. A strong attractive force was detected only at a CBD/cellulose interface, even when Ca2+ ions were present in high concentration. Direct estimation of CBD affinity for cellulose substrate by AFM would provide significant information on the interfacial interactions useful for the functional design of papermaking additives.

Asymmetric Polymer Bridging Between Starch‐Coated Colloidal Particles and Pulp Fibres by Cationic Polyacrylamide

AbstractInternal sizing agents are commonly used as additives in papermaking to impart hydrophobicity to paper. They are commonly added in the form of colloidal particles, stabilized by cationic starch. As an example we studied the deposition of micron‐sized Alkyl Ketene Dimer (AKD) particles on pulp fibres by cationic polyacrylamide (cPAM), a common flocculent. It was found that cPAM did not adsorb on AKD particles stabilized by cationic starch. Despite this inability to adsorb, cPAM was found to drastically improve the deposition of AKD particles on pulp fibres. This deposition was ascribed to asymmetric polymer bridging, a phenomenon observed by us before, while studying clay deposition on fibres by polyethylene oxide. In asymmetric polymer bridging between two types of particles, the bridging polymer first adsorbs on one type of particle, since it is unable to adsorb on the second type. Asymmetric polymer bridging occurs when the enthalpy gain on both surfaces exceeds the entropy loss. The kinetics of AKD deposition on fibres was found to agree with the predictions of the asymmetric bridging theory. In addition, an increase in bond strength with time was found, due to starch and cPAM reconfiguration. The increase in AKD retention by cPAM is also observed in experiments on a laboratory twin‐wire sheet former. Asymmetric polymer bridging by cPAM between starch‐coated AKD particles and fibres is compared with classical polymer bridging by cPAM between fibres and AKD particles coated by carboxymethylcellulose.

Introducing molasses as a new additive in papermaking

This study introduced, for the first time worldwide, molasses as an additive in papermaking. The introduction of molasses as an additive in papermaking resulted in paper composites with greater breaking length and remarkably higher water retention value (WRV), compared with paper that does not have molasses as an additive. Previous studies have shown that incorporating the cell wall microstructure of cellulose fibers with sucrose greatly enhanced the breaking length and WRV. It is well established in the literature that using gums (including starch) as additives in papermaking enhances paper strength. Molasses, which contains sucrose and gums (including starch) is a byproduct of the sugar industry and is cheaper than sucrose. Mercerization of pulp fibers before loading them with molasses was shown to greatly enhance the positive effects produced by loading with molasses.

Study on the Synthesis and Application of Starch‐graft‐Poly(AM‐co‐DADMAC) by Using a Complex Initiation System of CS‐KPS

AbstractA graft copolymer was synthesized by graft copolymerization of starch with acrylamide (AM) and diallyldimethylammonium chloride (DADMAC). The copolymerization was carried out using a complex initiation system of cerium sulfate (CS) and potassium persulfate (KPS). The effects of reaction conditions on graft copolymerization and use of these copolymers as additives in papermaking was investigated. Experiments showed that a graft copolymer with higher grafting level, higher intrinsic viscosity and higher cationic degree could be obtained by changing the method of monomer addition and by controlling the ratio of DADMAC to AM. The graft copolymerization was more effective when the complex initiation system of CS‐KPS was used. When adding 0.05% of the grafted starch [S‐g‐P(AM‐co‐DADMAC)] to the papermaking system, a higher filler retention was obtained than with cationic starch and cationic polyacrylamide when the cationic degree of S‐g‐P(AM‐co‐DADMAC) was 22% and its intrinsic viscosity was 7.35.

Seed storage hemicelluloses as wet-end additives in papermaking

Xyloglucans and galactomannans are examples of hemicelluloses that can be accumulated in seeds of many plants, being extensively studied and used for industrial applications. Guar gum and starch are polysaccharides currently used as wet-end additives in papermaking, whereas xyloglucans have never been reported to improve paper quality. In this work we show that different types of xyloglucans improved the mechanical properties of paper sheets without affecting the optical ones. Addition of 1% (w/w) of hemicelluloses to cellulosic pulp was able to increase by about 30% the mechanical properties such as burst and tear indexes. Seeds of several species could be used as source for the production of wet-end additives, since the results did not vary with the source of polysaccharides. Even if the utilisation of these hemicelluloses will not cost less than starch or guar gum, it might represent an important strategy for sustainable use of rainforest species.

Development of Environmentally Benign Pressure-Sensitive Adhesive Systems via Modification of Substrate Properties

Results are presented from a study on a novel approach for reducing the negative impact of pressure-sensitive adhesive (PSA) contaminants on paper recycling. Paper substrates are developed that can be easily removed from the recycling process via screening operations and retain their attached PSAs. A model series of hot-melt PSAs consisting of a styrene−isoprene−styrene/styrene−isoprene (SIS/SI) linear triblock, diblock copolymer blend, a pentaerythritol ester of rosin tackifying resin, and a naphthenic process oil were blended in combinations to produce a range of properties. These PSAs were attached to paper substrates with bulk and surface properties that were manipulated using commercial papermaking chemicals and dosages. A poly(amide epichlorohydrin) wet-strength resin was used to inhibit the fiberization of substrates. Removal efficiencies for PSAs coated on this paper were increased, but poor adhesion between the PSA films and paper substrates during repulping limited the improvement. It was found that the retention of the PSA increased linearly with its mechanical loss tangent indicating that properties of the PSA film could be manipulated to optimize removal efficiencies. It was also found that PSA−paper adhesion could be enhanced without restricting PSA properties by introducing an alkenyl ketene dimer size to the paper. The increased adhesion between PSA films and paper in an aqueous environment was achieved by raising the cellulose−water and lowering the cellulose−PSA interfacial energies. Removal efficiencies for PSAs attached to the sized, wet-strength paper substrates were >90% for all of the experimental hot-melt PSAs. Results of this study indicate that minor modifications made with common papermaking additives to paper used in PSA products can significantly reduce their impact on paper recycling.

Permanence of wood-free paper I: Paper-making additives in naturally degraded wood-free papers

Effects of pH, sizing agent, and starch on the natural deterioration of 45 printed wood-free papers stored 1–32 years was investigated in terms of MIT folding endurance, brightness, and L*a*b* values. The neutral and alkaline papers retained their folding endurances well and significantly lost their yellow color (b*) during storage. The folding endurance of the acidic papers stored more than 15 years showed a declining trend with increased storage time. The sizing agent content in the papers stored more than 10 years increased and the amount of starch decreased with increasing storage years. A larger amount of the sizing agents correlated with less folding endurance and more yellow color of the papers. The relation between the starch content and the degree of yellow color of the papers was unclear, and the endurance of the papers increased with the increase in starch content.

Isolation and Cationization of Barley Starches at Laboratory and Pilot Scale

ABSTRACTPrime barley starches were isolated in the laboratory by a conventional extraction procedure from regular (Condor), waxy (SB89528), and high amylose (Glacier) barleys; cationized; and evaluated as wet‐end additives in papermaking. The cationized barley starches showed functionality (contribution to paper strength) comparable that of to a commercial grade cationic corn starch. The laboratory evaluation was followed by a pilot plant study in which an air‐classified starch‐rich fraction from Condor barley was purified by a short wet‐extraction procedure. The starch obtained was then cationized, using a slightly different procedure than that used in the laboratory. Mass balances for starch extraction and cationization were obtained for the pilot plant study. The cationized barley starch needs evaluation in a Canadian paper mill.

Deposition of cationic polymeric pigments on pulp fibers

The potential advantage of using cationic pigments as wet-end additives in papermaking is in their expected ready deposition on anionic pulp fibers. The deposition characteristics of cationic polystyrene latex particles onto pulp fibers in a stirred system provide an information of the general behavior. The deposition proceeds at maximum rate in the pH region where the latex particles and the fibers have electrophoretic mobility of opposite sign. A departure from the expected behavior is observed in the pH region of latex destabilization. The failure of the coagulating latex to deposit indicates that hydrodynamic forces (introduced by mixing) acting on latex aggregates may prevent a deposition. An addition of neutral salt to the stirred system after deposition of latex particles was completed may result in a partial removal of latex particles from the fibers. The explanation for this reversible deposition is sought in an interplay of attractive forces between latex particles and fiber, the distance of their closest approach, and the size of particles upon which the hydrodynamic forces act. The behavior suggests that although the mutual attraction promotes deposition an intimate contact between latex particles and fiber is not established.