Mechanisms of strength and stiffness improvement of paper after PFI refining with a focus on the effect of fines

Motamedian, Hamid Reza; Halilović, Armin E.; Kulachenko, Artem

doi:10.1007/s10570-019-02349-5

Cited by 90 publications

(52 citation statements)

References 28 publications

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“…At equivalent energies, microfibre additions to primary pulp yielded higher bulk compared to multistage LC refining. Increased fibre flexibility induced by refining, as well as higher specific surface due to fibre cutting, fibrillation and generation of fines during the refining process promote inter-fibre bonding (Gorski et al 2012;Kerekes and Tam Doo 1985;Page 1989;Seth 2003) and lead to fibre network collapse and reduction of bulk (Forgacs 1963;Motamedian et al 2019;Retulainen et al 1993). Microfibre composites, on the other hand, were prepared by mixing long and intact fibres of primary pulp with a relatively small amount of highly developed fines and fibrils; this resulted in open construction handsheets with relatively higher bulk and improved mechanical strength.…”

Section: Pulp Freenessmentioning

confidence: 99%

Low consistency refined ligno-cellulose microfibre: an MFC alternative for high bulk, tear and tensile mechanical pulp papers

Jahangir

Olson

2020

Cellulose

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Low consistency (LC) refining of (chemi-) thermomechanical pulp (TMP) provides an energy efficient alternative to high consistency refining for pulp property development. However, the benefit of LC refining is often limited by excessive fibre shortening, lower tear strength and a reduction of bulk caused by the refining process. In this study, microfibres produced by LC refining of TMP and kraft pulp fibres were investigated for their reinforcement potential in high freeness mechanical pulp. Primary pulp at 645 mL Canadian Standard Freeness was LC refined to different energy targets as a baseline for mechanical and optical property development. In contrast, the same primary pulp was reinforced with different microfibre types in ratios that yielded the same specific energies of the baseline LC refined pulp. The study revealed that at equivalent energies, the addition of TMP microfibres to the high freeness primary pulp displayed tensile development identical to the LC refined pulp, with significantly improved tear and bulk. The addition of kraft microfibre to primary pulp produced the highest tensile and tear strength but compromised light scattering. Additionally, all microfibre composites showed improved elongation, as opposed to no notable change in elongation with conventional LC refining. This investigation proposes an alternative, cost-effective approach for developing high bulk, high strength mechanical pulp by limiting the extent of second stage refining and using LC refined microfibres for pulp reinforcement. The high tear-high bulk open construction of the composite paper is likely to benefit boxboard and packaging applications. Keywords Thermomechanical pulp (TMP) Á Microfibrillated cellulose (MFC) Á Low consistency refining (LC) Á Tear index Á Tensile energy absorption (TEA) Á Pulp reinforcement

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Section: Pulp Freenessmentioning

confidence: 99%

Low consistency refined ligno-cellulose microfibre: an MFC alternative for high bulk, tear and tensile mechanical pulp papers

Jahangir

Olson

2020

Cellulose

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“…While for secondary fines their effect on strength properties has extensively been reported by several researchers, this is not the case for primary fines, where only a few studies are available focusing on the effects of their removal or addition on paper technological properties (Bäckström et al 2008;Chauhan et al 2012;Ferreira et al 1999Ferreira et al , 2000Mayr et al 2017b;Motamedian et al 2019). Due to the differences in experimental designs, these studies did not always show consistent results.…”

Section: Introductionmentioning

confidence: 97%

“…In order to improve the strength properties of paper it is necessary to increase the relative bonded area and/ or specific bonding strength (Dasgupta 1994;Motamedian et al 2019). This increase can be achieved by sheet densification, which is positively influenced by addition of fine cellulosic materials such as micro or nanofibrillated celluloses or pulp fines, therefore leading to an increase in tensile properties (Bäckström et al 2008;Taipale et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…Due to their different morphological character, primary and secondary fines have a different effect on sheet properties. As the mainly fibrillar material of the secondary fines shows higher surface area and stronger swelling, it has a stronger effect on bonded area and therefore a stronger influence on strength properties of paper compared to the more blocky primary fines (Ferreira et al 2000;Fischer et al 2017;Mayr et al 2017a, b;Motamedian et al 2019;Odabas et al 2016). Still, also fine cellulosic materials defined as secondary fines can differ in their fibrillar material content, respectively their fibrillar area (Mayr et al 2017a).…”

Section: Introductionmentioning

confidence: 99%

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Softwood kraft pulp fines: application and impact on specific refining energy and strength properties

Mandlez

Zangl-Jagiello²,

Eckhart

et al. 2020

Cellulose

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Along with the emergence of micro and nanofibrillated celluloses and their application in papermaking, the influence of the so called fines fraction of pulps on both process and product properties has received increasing research interest in recent years. Several researchers have experimented with primary and/or secondary pulp fines to assess their effects on paper properties with not always consistent results. Our work focuses on the targeted application of the primary fines fraction of an unbleached softwood kraft pulp. The primary fines are separated from the pulp to be subsequently added to achieve blends of $$5\%, 9\%$$ 5 % , 9 % and $$12\%$$ 12 % primary fines content. These blends were then refined in a PFI mill to evaluate the effect of the primary fines on refining as well as on paper properties of hand sheets prepared from these pulps. It is shown that the addition of primary fines enhances tensile strength in the unrefined and slightly refined state, while the maximum tensile strength of the highly refined reference pulp is not increased. A slightly increased dewatering resistance (Schopper Riegler) at comparable air permeability (Gurley) for a given tensile strength was also observed. The linear relationship between tensile index and apparent sheet density seems to be affected in the unrefined and slightly refined state where the breaking length of the fines enriched samples is higher for a given apparent density.

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“…LC refining would make it possible to produce more fibrillar fines also called secondary fines (Odabas et al 2016) and thereby further increase the network strength at maintained bulk (Ljungqvist et al 2014. Also Motamedian et al (2019) found that an increased number of fibrillar fines increases the strength of paper. This was explained by the ability of fibrillar fines to reinforce the bonds in the fibre network.…”

Section: Introductionmentioning

confidence: 97%

Low-consistency refining of CTMP targeting high strength and bulk: effect of filling pattern and trial scale

Berg

Hellstadius

Lundfors

et al. 2020

Nordic Pulp &Amp; Paper Research Journal

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Chemithermomechanical pulp (CTMP) is often used in central layers of multiply paperboards due to its high bulk and strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to optimize process conditions in low-consistency (LC) refining, i. e. to select or ultimately develop new optimal LC refiner filling patterns, in order to produce fibrillar fines and improve the separation of fibres from each other while preserving the natural fibre morphology as much as possible. Furthermore, the aim is to evaluate if this type of work can be done at laboratory-scale or if it is necessary to run trials in pilot- or mill-scale in order to get relevant answers. First stage CTMP made from Norway spruce (Picea abies) was LC refined in mill-, pilot- and laboratory-scale trials and with different filling patterns. The results show that an LR1 laboratory refiner can favourably be used instead of larger refiners in order to characterize CTMP with regard to tensile index and z-strength versus bulk. A fine filling pattern resulted in CTMP with higher tensile index, z-strength and energy efficiency at maintained bulk compared to a standard filling pattern.

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Mechanisms of strength and stiffness improvement of paper after PFI refining with a focus on the effect of fines

Cited by 90 publications

References 28 publications

Low consistency refined ligno-cellulose microfibre: an MFC alternative for high bulk, tear and tensile mechanical pulp papers

Low consistency refined ligno-cellulose microfibre: an MFC alternative for high bulk, tear and tensile mechanical pulp papers

Softwood kraft pulp fines: application and impact on specific refining energy and strength properties

Low-consistency refining of CTMP targeting high strength and bulk: effect of filling pattern and trial scale

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