Preparation and Application of Precipitated Calcium Carbonate-Cellulose Nanofibril Composite Filler in Papermaking

다국어 초록 (Multilingual Abstract)

Nanotechnology is an emerging area of science and technology that will revolutionize materials use in the 21st century. Recently, as a cellulosic nanomaterial, cellulose nanofibril (CNF) have attracted much attention and shown enormous potential in the field of pulp and paper technology. Mechanical treatment has been the primary disintegration technique used to produce CNFs. The decreased size of fibers from micro-scale to nano-scale in width by mechanical force offers a new potential with unique properties such as high mechanical strength, large specific surface area, high aspect ratio, barrier properties, biodegradability and biocompatibility. Moreover, CNFs form a network already in very dilute aqueous suspensions. Therefore, it seems that they can flocculate small particles such as fines and fillers effectively.
In this study, the effect of CNFs on the flocculation of precipitated calcium carbonate (PCC) was elucidated. The PCC aggregation was analyzed using particle size measurement, photometric dispersion analysis (PDA), and scanning electron microscopy (SEM). The result showed that CNFs can be used to flocculate particles such as calcium carbonate fillers and the CNFs functioned as bridges between the two PCC particles. Although the synthetic polymers are much more effective than the CNFs because of their versatile tailorability, a noticeable reflocculation capability was observed in one- and two-component systems that consisted of CNFs. The presence of cationic starch could strengthen and induce formation of CNF/starch bridges between filler particles. A noticeable reflocculation capability was also observed in one- and two-component systems that consisted of CNFs.
Many researchers have reported to use CNFs as strength additives in paper and paperboard products. With the ability to flocculate filler of CNFs, a concept of composite filler was developed by using CNF, PCC and cationic starch (C-starch) in this work. Moreover, cellulose nanofibrils were utilized in two different ways: a PCC-CNF composite filler and a papermaking additive in sheet forming. Almost 90% filler retention was achieved with the use of PCC-CNF composite fillers. The paper filled with the composite fillers had much higher bursting and tensile strengths than conventional PCC loading. It was also found that the paper prepared with PCC-CNF composite fillers became denser with increasing the filler content of paper. Even with increased density, composite fillers containing handsheet showed better light scattering than conventional PCC loaded handsheet.
However, CNFs can form a cross-linked network with a pseudoplastic behavior, even in very dilute aqueous suspensions duo to their large specific surface area and high aspect ratio. They are expected to affect sheet dewatering properties negatively due to high water retention capacity. The effect of CNF on the drainage properties of pulp furnish and on the strength properties of paper sheets were also studied. An undesirable increase in drainage time was observed which might be due to that the pre-flocculated PCC-CNF composite filler get a higher retention of CNF in fiber web than CNF used as a papermaking additive. But a favorable effect on solid content after press was observed. This may be considered as that the water holding ability of the CNF was outweighed by the non-swelling PCC at proper dosage of CNF. Although CNFs will cause dewatering difficulties in papermaking applications, it is expected that these difficulties will be overcome by optimal selection of CNF adding method and filler content which will not influence the pressability of the sheet in the wet end.

목차 (Table of Contents)

• CONTENTS
• Chapter 1 1
• General introduction 1
• 1. Background 2
• 2. Objectives 6
• Chapter 2 8
• Literature Review 8
• 1. Precipitated Calcium Carbonate (PCC) and basic flocculation mechanisms 9
• 2. Nanotechnology 12
• 3. Cellulose and nanocellulose 13
• 4. Production of cellulose nanofibril and its characteristics 16
• 4.1 Production of cellulose nanofibril (CNF) 16
• 4.2. Properties of CNF 19
• 5. Utilization of CNFs in papermaking 20
• Chapter 3 23
• Utilizing of Cellulose Nanofibril as an Eco-friendly Flocculant for Filler Flocculation in Papermaking 23
• 1. Introduction 24
• 2. Experimental 27
• 2.1. Materials 27
• 2.2. Methods 28
• 2.2.1. Preparation of CNF 28
• 2.2.2. Evaluation of the properties of CNF 29
• 2.2.3. Evaluation of the flocculation behavior of PCC with CNF 33
• 3. Result and discussion 35
• 3.1. General characterization of CNF 35
• 3.2. Flocculation of PCC with CNF 40
• 3.3. Flocculation of PCC with two component systems 49
• 3.4. Morphology of PCC flocculated by polymers and CNF 54
• 4. Conclusions 56
• Chapter 4 57
• Effect of Precipitated Calcium Carbonate - Cellulose Nanofibril Composite Filler on Paper Properties 57
• 1. Introduction 58
• 2. Experimental 60
• 2.1. Materials 60
• 2.2 Methods 61
• 2.2.1. Preparation of CNF 61
• 2.2.2. Preparation of PCC-CNF composite filler 61
• 2.2.3. Hand-sheet preparation 62
• 2.2.4. Paper analysis 63
• 2.2.5. Field Emission SEM analysis 63
• 3. Result and discussion 65
• 3.1. Filler retention 65
• 3.2. Strength properties 67
• 3.3. Sheet formation and apparent density 71
• 3.4. Opacity 74
• 4. Conclusions 75
• Chapter 5 76
• Effect of Cellulose Nanofibrils on the Furnish Dewatering and Properties of Fine Paper 76
• 1. Introduction 77
• 2. Experimental 80
• 2.1. Materials 80
• 2.2. Methods 81
• 2.2.1. CNF production 81
• 2.2.2. Characterization of CNF 82
• 2.2.3. Hand-sheet preparation 83
• 2.2.4. Paper analysis 84
• 2.2.5 Field Emission SEM analysis 84
• 3. Result and discussion 85
• 3.1. General characterization of CNF 85
• 3.2. Pulp slurry drainage 87
• 3.2. Paper properties 92
• 3.2.1. Filler retention 92
• 3.2.2. Apparent density and air permeability 94
• 3.2.3. Strength properties 97
• 3.2.4. Opacity 99
• 4. Conclusions 102
• Chapter 6 103
• General conclusions 103
• References 107