Kr Stack

Study of the interaction between poly(ethylene oxide) and phenol-formaldehyde resin

Abstract Interactions between poly(ethylene oxide) and phenol—formaldehyde resin play important roles in the mechanism by which the two polymers improve fibre retention in the papermaking process. These were investigated at the concentration level and shear conditions found in this process. The results indicate that the complex formed varies with pH and ionic strength over a very narrow range of conditions, and that the self association of the resin plays an important part in the quantity of resin in the complex. Because the amount of resin interacting with the polyethylene oxide appears to be related to the molecular weight, and hence chain length, of the two polymers, cooperative binding of the polymers seems to be involved. A minimum size of the network was found to be necessary for the polymers to improve fibre retention.

Evaluation of Various Phenolformaldehyde Resins in the Phenolformaldehyde Resin—Polyethyleneoxide Dual Retention Aid System

Abstract Retention performance of the polyethylene oxide (PEO)-phenolformaldehyde resin (PFR) retention aid system is affected by the chemical structure and the molecular weight distribution of PFR. 1NMR and high performance liquid chromatography have been used to characterise various resole and novolak-based resins. Of the resins examined, those with the highest molecular weight gave the greatest retention improvement. The type of substitution around the aromatic ring of the resin appears to affect the interaction with PEO and the size and structure of the network formed when PFR and PEO are mixed together.

An Innovative Approach Characterising the Interactions Leading to Pitch Deposition

Abstract In the production of mechanical pulp for paper manufacture, resinous material is released from the wood. This resinous material forms colloidal dispersions which can agglomerate and deposit onto surfaces. These deposits are known as pitch. Pitch has been cited in the literature as early as the 1920s but there is still much more to learn about the interactions that occur in its formation. We know what the major components of pitch are and how these wood extractives can vary with type, location and age of the tree as well as seasonal effects. It is known and cited in the literature that the four major components of pitch are fatty acids (namely those of chain length C12–C20), resin acids, triglycerides, and steryl esters. Due to the complexity of a four component system it was decided to focus the initial study on a two component system, namely that of a resin and a fatty acid. This paper will attempt to explain the chemical interactions that occur at a molecular level between these two wood extractive components. The fatty acids were divided into two studies, involving the chain length and degrees of saturation, and the resin acids were separated into three classes; aromatic class (dehydroabietic acid), conjugated diene class (abietic acid), and alkene class (isopimaric acid). The interaction has been studied using deposition studies and molecular modelling. Trends in classes of each component were contrary to our initial theory that the amount of pitch deposited was related to the solubility of the organic compounds in water. Further studies indicated that a physical interaction in the form of hydrogen bonding was occurring between the resin acid and fatty acid and that the method in which the molecules interact with each other and the surrounding water molecules affect deposition. Differences in deposition behaviour was found when the type of resin acid, the fatty acid chain length, and the fatty acids degree of unsaturation were varied. It is proposed that the aromatic class of resin acid (dehydroabietic acid) forms hydrogen bonds over the aromatic ring, whereas the non‐aromatic classes of resin acid simply dimerise at the carboxylic head groups. These differences in orientation of the molecules affects the interaction of the rest of the molecule with the surrounding water molecules and hence its solubility and deposition abilities.

Adsorption studies of phenolformaldehyde resin onto cellulose fibres

Abstract Adsorption of phenolformaldehyde resin (PFR) onto microcrystalline cellulose was investigated as a function of pH. ionic strength, temperature and shear. The effect of adsorption was also studied by measuring the electrophoretic mobility of the cellulose particles. Adsorption was found to occur above a critical ionic strength. Suppression of the electrical double layer and reduced solubility of PFR appear to be necessary to promote adsorption. Increasing the intensity and duration of shear was found to increase the amount of PFR adsorbed. In the presence of high molecular weight poly(ethylene oxide) (PEO), complex formation between PEO and PFR also competes with the interaction between PFR and the cellulose particles. The mobility data indicate that the PFR directly affects the cellulose surface rather than the PEO.

Structure of wood extract colloids and effect of CaCl2 on the molecular mobility

Electron paramagnetic resonance (EPR) was used to study the colloidal structure of model wood extractive colloids composed of a resin acid (abietic acid), a fatty acid (oleic acid) and a triglyceride (triolein). Two nitroxides were chosen as EPR probes to gain a greater understanding of the different regions of the colloid in order to assess the current proposed models of the structure of the wood extractive colloid. A non-polar nitroxide probed non-polar regions of the colloid, such as triglycerides, while a surfactant-type nitroxide probed regions occupied by fatty acids. The effect of varying the amounts of each of the model colloid components on the structure of the colloid and its interaction with the probe was investigated. Results of the EPR study confirm the existence of a hydrophobic core. However, surface tension and EPR results suggest that the outer layer of the colloid is composed of mostly resin acids. It is proposed that a fatty acid layer exists between the resin acids and triglycerides and is sufficiently mobile to move between them. The addition of salt (CaCl2) was found to

Effect of copper and other trace metal addition to pulp and paper wastewater

Porous pots were used to mimic, on a laboratory scale, an industrial activated sludge plant from a thermomechanical pulp and news print paper mill. Trace metal additions of Ca, Co, Cu, Fe(III), and Mg were found to improve chemical oxygen demand removal from 82% to 86 to 87%. Copper (0.1 to 1.0 mg/L) was also found to be beneficial in significantly inhibiting the growth of filamentous bacteria, contributing to a reduction of 20 to 45% in sludge volume index (SVI) with improved settle ability and decreased bulking. However, at levels of 1.0 mg/L and higher, the concentration of Cu in the porous pot effluent would potentially exceed guidelines for receiving waters. The fate and impact of Cu was affected by the presence of other trace metals, in particular Mg and Ca. The addition of Mg or Ca along with 0.5 mg/L Cu increased the amount of Cu in the aqueous phase to levels that would potentially exceed government environmental guidelines. Calcium addition was also found to inhibit the effect of Cu in reducing filamentous bacteria and SVI.