ATMP pilot refining trials on Norway spruce were conducted. The ATMP configuration consists of selective wood disintegration and targeted application of chemicals when defibration already is initiated in order to achieve energy-efficient final fibre separation and development. ATMP was compared to TMP and RTS. The TMP like character was maintained despite of differences in pre-treatment, chemicals and primary stage refining energies. The fractional composition of the pulps was, however, altered. Bauer McNett R14 fraction exhibited the largest differences followed by P200 fraction. Thus different process alternatives produced pulps with different fingerprints. The amount of the R14 fibres is important as these tend to cause surface roughness impairing printability. Regardless of strategy, the ATMP pulp properties at equal tensile index (44 Nm/g) were equal or superior to those achieved by TMP or RTS refining. The main difference was the required specific energy input, ranging from 1.71 (TMP) to 1.05 MWh/BDT (ATMP with bisulphite addition). Primary stage refining was explored from multiple trials with the same process configuration and chemistry. The higher the specific energy applied the better is the energy efficiency. Furthermore established refining theories appear inadequate in describing the differences between process alternatives with respect to energy efficiency and pulp property development.

The objective of this study is to analyze and foresee potential outliers in pulp and handsheet properties for larger data sets. The method is divided into two parts comprising a generalized Extreme Studentized Deviate (ESD) procedure for laboratory data followed by an analysis of the findings using a multivariable model based on internal variables (i. e. process variables like consistency and fiber residence time inside the refiner) as predictors. The process data used in this has been obtained from CD-82 refiners and from a laboratory test program perspective, the test series were extensive. In the procedure more than 290 samples were analyzed to get a stable outlier detection. Note, this set was obtained from pulp at one specific operating condition. When comparing such "secured data sets" with process data it is shown that an extended procedure must be performed to get data sets which cover different operating points. Here 100 pulp samples at different process conditions were analyzed. It is shown that only about 60 percent of all tensile index measurements were accepted in the procedure which indicates the need to oversample when performing extensive trials to get reliable pulp and handsheet properties in TMP and CTMP processes.

Comparative pilot refining trials with Norway spruce chips were conducted in order to gain a better understanding of the principal mechanisms on fibre level for achieving radical energy reduction in the novel ATMP refining concept. The ATMP pulping configurations proved superior energy efficiency in pulp quality development, compared to TMP, RTS and F-RTS concepts. Development of high tensile strength did not progress at the expense of light scattering, even with process chemicals present. Extensive testing of individual particles in long fibre, middle and fines fractions in combination with analyses of properties of fraction sheets has shown that Impressafiner/Fiberizer pre-treatment opens the wood structure, allowing for early development of desired single fibre properties and generation of fibrillar fines. Peroxide combined with magnesium hydroxide affected the interior of the fibre walls, thereby facilitating improved fibre flexibility, collapsibility and swelling. Bisulphite mainly affected the fibre length distribution, reducing the coarse fraction R14 and promoting the generation of considerable amounts of coarse fines and middle fraction particles.

Defibration and fibre development patterns were investigated for the novel ATMP refining process, based on pilot scale trials with Norway spruce chips. ATMP refining with different chemical agents was compared to RTS refining with and without Impressa-finer (RT) and Fiberizer (F) pre-treatment. RT-F pre-treatment significantly improved both initial defibration, axial fibre splitting and fibre flexibility, compared to RTS primary stage refining without pre-treatment. Both types of investigated ATMP process chemistry - hydrogen peroxide combined with magnesium hydroxide under alkaline conditions (P) or acid sodium bisulphite (S) added to the primary refiner dilution water - further improved the fibre separation of RT-F pre-treated wood during primary stage RTS refining. This is largely attributed to enhanced fibre swelling. S-treatment facilitated frequent fibre separation within or close to the S2 wall layer, yielding extremely low shive levels and well-fibrillated, thin-walled fibres early in the process. S-treatment also rendered stiffer fibres, which made them susceptible to breakage, axial splitting and internal delamination. P-application is proposed to affect primarily the interior layers of the fibre walls, facilitating rapid fibre wall swelling towards the lumen, fibre softening and flexibilization.

This review is the first part of a comprehensive review of hydrophobisation of lignocellulosic materials. The purpose of this review has been to compare physical hydrophobisation methods of lignocellulosic materials. We have compared molecular physical adsorption with plasma etching and grafting. Adsorption methods are facile and rely upon the simple mixing or coating of the substrate with the hydrophobing agent. However, none of the surfactant-based methods reviewed here reach contact angles above 90°, making them unsuitable for applications where a high degree of hydrophobisation is required. Nevertheless, surfactant based methods are well suited for compatibilising the lignocellulosic material with a hydrophobic matrix/polymer in cases where only a slight decrease in the hydrophilicity of the lignocellulosic substrate is required. On the other hand, wax- and lignin-based coatings can provide high hydrophobicity to the substrates. Plasma etching requires a more complex set-up but is relatively cheap. By physically etching the surface with or without the deposition of a hydrophobic coating, the material is rendered hydrophobic, reaching contact angles well above 120°. A major drawback of this method is the need for a plasma etching set-up, and some researchers co-deposit fluorine-based layers, which have a negative environmental impact. An alternative is plasma grafting, where single molecules are grafted on, initiated by radicals formed in the plasma. This method also requires a plasma set-up, but the vast majority of hydrophobic species can be grafted on. Examples include fatty acids, silanes and alkanes. Contact angles well above 110° are achieved by this method, and both fluorine and non-toxic species may be used for grafting. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).

This review is the third part of a series of reviews on hydrophobization of lignocellulosic materials, a relevant topic nowadays, due to the need to replace fossil fuel-based materials. The review provides an overview of the hydrophobization of lignocellulosic materials by polymer adsorption, and both chemical and radiation-induced grafting of polymers. While adsorbed polymers are only attached to the surfaces by physical interactions, grafted polymers are chemically bonded to the materials. Radiation-induced grafting is typically the most environmentally friendly grafting technique, even though it provides little control on the polymer synthesis. On the other hand, controlled radical polymerization reactions are more complex but allow for the synthesis of polymers with elaborated architectures and well-defined properties. Overall, a wide range of contact angles can be obtained by polymer adsorption and grafting, from a slight increase in hydrophobicity to superhydrophobic properties. The choice of modification technique depends on the end-use of the modified material, but there is a clear trend towards the use of more environmentally friendly chemicals and processes and the grafting of polymers with complex structures. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).

The purpose of this paper is to report about our experiences with treating softwood mechanical pulp (MP) with DBA directly injected into the gap of high consistency (HC) refiners used as chemical reactors to improve the competitiveness and the ecological footprint of (C)TMP based products. After the description of the main factors and pros and cons of conventional oxidative and reductive bleaching of sofhvood MP the basic principles of the treatment of MP with DBA in the (C)TMP refiner are outlined. By means of exemplary results of trials in lab, pilot and mill scale as well as of productions the main advantages of "DBA in (C)TMP" are illustrated: efficient brightness gain, reduction of anionic trash, high wood yield, reduction of hard chelating agents, saving of refining energy and increase of strength properties. Using the example of Norske Skog Skogn it is demonstrated how the system works in practice in the production of high bright and standard newsprint made from normal and lower quality wood. Finally it is pointed out that to a certain extent DBAs can be tailored to the needs of the respective mill.

We have in this paper investigated how water sorbs to cellulose. We found that both cellulose nanofibril (CNF) and cellulose nanocrystal (CNC) films swell similarly, as they are both mainly composed of cellulose. CNF/CNC films subjected to water at 0.018 kg/m3 at 25 °C and 39 °C, showed a decrease in swelling from ~ 8 to 2%. This deswelling increased the tensile index of CNF-films by ~ 13%. By molecular modeling of fibril swelling, we found that water sorbed to cellulose exhibits a decreased diffusion constant compared to bulk water. We quantified this change and showed that diffusion of sorbed water displays less dependency on swelling temperature compared to bulk water diffusion. To our knowledge, this has not previously been demonstrated by molecular modeling. The difference between bulk water diffusion (DWW) and diffusion of water sorbed to cellulose (DCC) increased from DWW − DCC ~ 3 × 10–5 cm/s2 at 25 °C to DWW − DCC ~ 8.3 × 10–5 cm/s2 at 100 °C. Moreover, water molecules spent less successive time sorbed to a fibril at higher temperatures. © 2022, The Author(s).