Bleached Chemithermomechanical Pulp Research Articles

Improved thermomechanical and rheological properties of polypropylene composites with thermomechanical pulp for injection molding

AbstractMaterial extrusion and injection molding are prevalent in polymer processing, but wood fiber‐reinforced polymer composites offer eco‐friendly alternatives for industries like automotive, and aviation. Our study explores biocomposites using bleached chemi‐thermomechanical pulp (BCTMP) and polypropylene (PP). BCTMP is rich in cellulose and hemicellulose and quite hydrophilic, while PP's hydrophobic structure creates a disconnect to creating a composite of the two. Traditional methods add costly coupling agents like maleic anhydride polypropylene (MAPP) in an attempt to enhance the adhesion properties of wood‐plastic composites. However, it is worth noting that even in the presence of MAPP, PP maintains its high hydrophobicity and low surface energy, despite exhibiting considerable heterogeneity. Further complexity arises from the thermal degradation characteristics of BCTMP during the melting processing of PP. Our proposed method involves premixing via cryo and planetary ball milling. This boosts PP and BCTMP adhesion, enhancing dispersion quality and mechanical properties without needing coupling agents. Moreover, the premixing of BCTMP and PP forms a thermal buffer layer around BCTMP, minimizing its thermal degradation during processing. This process also ensures even distribution of BCTMP into PP, resulting in a 200% rise in Young's modulus with 30 wt% BCTMP without compromising ultimate tensile strength.Highlights Exploration of biocomposites using bleached chemi‐thermomechanical pulp (BCTMP) and polypropylene (PP) thorough injection molding Implementation of premixing to enhance PP/BCTMP adhesion without coupling agents Premixing reduces thermal degradation of BCTMP, enhances dispersion, and improves mechanical properties Achieving a 200% increase in Young's modulus with 30% BCTMP incorporation, while maintaining ultimate tensile strength

Energy absorption and resilience in quasi-static loading of foam-formed cellulose fibre materials

To avoid microplastic pollution, there is an urgent need to replace fossil-based cushioning materials in packaging with easily recyclable alternatives. Here, we investigated the potential of lightweight cellulose fibre materials as a solution for mechanical protection. The quasi-static compression was studied among a vast set of 129 different foam-formed trial points with material density ranging from 21 kg/m3 to 123 kg/m3. The trial points included two different fibre types, bleached softwood kraft pulp (BSKP) and bleached chemithermomechanical pulp (CTMP), with varied refining level, pulp consistency, foaming conditions, surfactant type, strength additives, and final material density and thickness. Besides a correlation analysis of factors affecting compression stress and resilience, the results were reflected against a new theoretical prediction of energy absorption for an ideal low-density random fibre network. The theory predicts the initially-high cushion factor to rapidly drop down to the level of 4‒5 at 40‒80% compression. A similar behaviour was seen among the actual samples, despite their various non-ideal features. At 50% compression, the average cushion factor across the whole data set was 4.84 ± 0.10, being close to the theoretical prediction of 4.61 for the ideal case. The smallest cushion factor of 3.6 was found for a CTMP sample. The recovery from compression varied slightly among the samples and appeared highest for the material density of 60‒100 kg/m3, following the predicted proportion of non-buckled fibre segments. According to the results, cellulose fibre-based cushions have a soft initial response, which is preferable for fragile items.Graphical abstract

Response of partial substitution of MgO for NaOH as the alkali source in hydrogen peroxide bleaching to properties of triploid poplar chemi-thermomechanical pulp

Given the current scarcity of wood fiber resources, it is imperative to investigate the potential of employing weak alkaline hydrogen peroxide for bleaching high-yield pulp (HYP) to meet the increasing demands for paper and paperboard. This work presents an investigation into the characteristics of triploid poplar chemi-thermomechanical pulp (CTMP) hydrogen peroxide bleaching, including the brightness, bleaching yield, bulk, physical strength, and contents of carbohydrates and lignin. The findings show that partial substitution of MgO for NaOH as an alkali source could improve the yield and bulk of the bleached CTMP. When the substitution ratio of MgO for NaOH reached 75 %, the brightness of 74.62 % ISO for the bleached pulp dropped by only 0.47 percent points but the bulk of 2.21 cm3/g increased by 5.74 % compared to those of the control, respectively. Meanwhile, the yield of the bleached CTMP could reach 93.45 %, 5.07 percent points higher than that of the control. The results would be of benefit to the HYP enterprises concerned.

Energy saving potential of interstage screen fractionation for production of board grade BCTMP

Over the last few decades, the continuing decline in mechanical pulp-based grades has led pulp producers to modify operations and implement measures to reduce production costs in order to stay competitive. In spite of a considerable effort to reduce energy consumption, the latter is still a major portion of production costs in the process of making bleached chemithermomechanical pulp (BCTMP). In this study, we evaluated the impact of interstage screening fractionation (ISSF) and secondary refining strategy for producing BCTMP with the objective of reducing refining energy consumption while maintaining or improving bulk and strength properties. In the first step and to establish a baseline for a mill’s existing configuration, the collected primary refined pulp and reject streams from the ISSF were refined in a high consistency (HC) refiner to target freeness levels. The accepts and refined rejects streams were recombined, and their properties were compared to those of the refined primary pulp. The results showed that, at a given freeness of 400 mL and compared to the control case (without fractionation), the ISSF using an 0.070 in. basket followed by rejects refining could lead to about 25% energy saving in the second stage HC refining. Handsheet properties showed that utilization of ISSF could produce BCTMP with higher bulk and similar average fiber length and tear index. However, a slight reduction in tensile strength was observed. In the second set of trials, the primary refined pulp and the rejects from the ISSF using the 0.070 in. basket were refined by a low-consistency (LC) refiner. The results showed that, at the same freeness of 400 mL and compared to refined primary pulp, the ISSF saved about 26% in net LC refining energy. At a specific edge load (SEL) of 0.4 J/m, the produced pulp had similar bulk and strength properties compared to those of the control sample. A higher SEL of 0.6 J/m in LC refining could further decrease net refining energy consumption; however, it also led to reduction in fiber length, bulk, and strength properties.

Characterization of volatile organic compounds in food contact paperboards and elucidation of their potential origins from the perspective of the raw materials

Characterizing the volatile organic compounds (VOCs) in food contact paperboards and clarifying the origins of these VOCs are crucial to ensure the quality of the paperboards. Herein, VOCs present in raw paperboards (RPBs) intended for food contact and related raw materials comprising eucalyptus wood chips (WCs), bleached chemi-thermomechanical pulp (BCTMP), and dry pulp sheets (DPSs), were characterized using headspace solid-phase microextraction comprehensive two-dimensional gas chromatography quadrupole-time-of-flight mass spectrometry, by which 331, 191, 154, and 295 VOCs of 6 chemical categories were identified, respectively. It was found by chemometrics that bleaching significantly impacted the VOCs present in the RPBs and the DPSs in terms of both the number and chemical category of the VOCs, and that the DPSs exhibited higher correlations with the RPBs than other raw materials in terms of the VOCs. Most importantly, 153 VOCs present in the RPBs could be traced to the raw materials due to their co-occurrence, whereas the remaining 178 VOCs were proposed to originate from the RPBs production stage, relating to processing aids (22%), functional additives (17%), degradation products (51%), and contaminants (3%). Our results provided valuable references for the paper industry and were beneficial to promote food safety and the well-being of consumers.

Chemical addition to wet webs using foam application

In papermaking, the conventional way to add chemicals to the web is to dose them into the fiber stock and form the paper afterwards. However, in many cases, adding chemicals directly to the stock is challenging. For example, strength aids tend to increase flocculation in the stock, which limits the addition amounts of those aids. The need for better performance of paper (and paperboard) products has given rise to the need for functionalization of paper. Adding such functional chemicals to the stock is usually rather inefficient. Hence, novel methods are needed to add chemicals to the paper bulk. One such method is dosing chemicals to the wet web via foam application. In this study, we built a laboratory-scale sheetfed dynamic foam application device and utilized it to study addition of starch to wet bleached chemithermomechanical pulp (BCTMP) paper handsheets. The impact of parameters such as vacuum level, the amount of added chemical, and the viscosity of the foaming liquid on the penetration of starch into the wet web was explored. Starch penetration into wet webs was measured via iodine-potassium iodide staining, followed by image analysis. According to our results, controlling the viscosity of the foaming liquid gives the best possibility to control the penetration.

Enhanced bleachability of chemi-thermomechanical pulp by hydrogen peroxide bleaching in ethanol-water media

Hydrogen peroxide (H2O2) bleaching in ethanol-water media was used to improve the bleaching efficiency of the chemi-thermomechanical pulp (CTMP). The brightness of CTMP increased and the yellowness decreased when the ethanol ratio was increased to 50%. However, when more than 50% ethanol was added, the brightness decreased, and the yellowness increased. In general, H2O2 bleaching in ethanol-water media, except for 100% ethanol, improved the optical properties of CTMP compared to conventional H2O2 bleaching. Moreover, the chemical composition of CTMP did not alter significantly. The best bleaching condition for CTMP was observed in 50% ethanol at a bleaching temperature and time of 80 °C and 120 min, respectively. The brightness of CTMP under this condition increased by approximately 22% compared with conventional H2O2 bleached CTMP. Principal component analysis (PCA) revealed that the optical properties of bleached CTMP were affected by the structural changes of the aromatic ring and carbonyl group in lignin and carbonyl group in hemicellulose. Consequently, the specific optimal ratio of ethanol that could improve the optical properties of CTMP was determined. The results can serve as a reference for fabricating improved CTMP for its practical application in high-grade papermaking.

Use of Endoglucanase and Accessory Enzymes to Facilitate Mechanical Pulp Nanofibrillation

Although selective enzyme treatments have been used to successfully fibrillate chemical pulps, high lignin-containing mechanical pulps have proven to be more recalcitrant. When a bleached chemi-thermomechanical pulp (BCTMP) was sulfonated prior to enzymatic treatment, relatively good fibrillation was achieved, although some pulp hydrolysis occurred after 6 h hydrolysis when using a commercial cellulase enzyme preparation (Cellic CTec 3). To try to minimize pulp losses, various enzyme cocktails, including endoglucanase (EG), xylanase, mannanase, and lytic polysaccharide monooxygenase (LPMO), were assessed for their ability to enhance fibrillation while minimizing cellulose hydrolysis. It was apparent that the yield as well as the zeta potential of the lignin-containing cellulose nanofibrils increased with enzyme treatment. This was likely due to an increase in surface charge and a decrease in particle size after LPMO and hemicellulase treatments, respectively. When carbohydrate-binding modules (CBMs) were used to quantify fiber changes, it was apparent that sulfonation had increased the accessibility of enzymes, while the combined action of the hemicellulases and LPMO increased EG accessibility to the less-ordered regions of the mechanical pulp, resulting in enhanced fibrillation. This work described, for the first time, the synergistic action of EG and various accessory enzymes enhancing mechanical pulp nanofibrillation.

Kraft, BCTMP, and TMP dewatering behaviour along the axis of a screw press

The drainage- and dewatering-controlling mechanisms in a screw press were detailed in this work. Three pulps (kraft pulp, bleached chemi-thermomechanical pulp, and thermomechanical pulp) were studied to compare a wide range of wood fibre types. The dewatering was controlled by the screw press parameters and the pulps’ properties. Filtration was found to be the controlling mechanism in the first part of the screw press for the three pulps, and it was less important when the fines content was greater. In the compression zone, the degree of compression was affected by the pulp flexibility and the fibres’ tendency to entangle. Filtrate flow rate monitoring along the screw press could be a good indicator of where the transition from filtration to consolidation occurs. The pressure along the screw press did not change much in the filtration zone, and it notably increased near the discharge end. When the drainage was very high, the pulp feed increased, causing the pulp axial velocity in the end part to be greater than the screw’s linear advance.

Mixed-Refining of BCTMP and LBKP for Lightweight Papers

Refining of pulp is an important stage on papermaking process in developing the fiber properties in order to meet the paper quality requirements. Separate refining is general practice implemented by industry which uses more than one kind of pulp. However, combined or mixed refining of two kinds of pulp has an advantageous especially in the view of energy. Mixed refining of BCTMP (Bleached Chemi-Thermo-Mechanical Pulp) and LBKP (Leaf Bleached Kraft Pulp) mixture has been investigated. The experiments were carried out at a mixture composition of 10% BCTMP and 90% LBKP compared to the same mixture composition of pulps which were refined separately, as well as 100% BCTMP and 100% LBKP. The result showed that the average fiber length of pulps mixture from mixed refining was the lowest, but its’ maximum fiber length was still quite good, closed to LBKP fibers. Compared to separate refining, mixed refining of pulps produced good sheet strength, while the other sheet properties were not significantly influenced. Keywords: BCTMP, LBKP, refining, mixed refining DOI : 10.7176/CMR/11-8-04 Publication date :October 31 st 2019

Preparation of cellulose nanofibers by TEMPO-oxidation of bleached chemi-thermomechanical pulp for cement applications

Hardwood bleached chemi-thermomechanical pulp (BCTMP) was converted to cellulose nanofibers by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) catalyzed oxidization along with mechanical defibrillation process. The TEMPO reaction was evaluated based on the delignification, carboxylate content of cellulose and the yield of the insoluble component. Cellulose nanofibers were characterized by conductometry, Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA) as well as X-ray diffraction (XRD) techniques. Minimum 10 mmol/g NaClO addition was needed to obtain meaningful carboxylate content and easy defibrillation by using high shear mixing. TEMPO-catalyzed oxidization process removed 74% of pentosans and 80% of lignin from bleached chemi-thermomechanical hardwood pulp while 13% of cellulose was also lost. CNF with 1.44 mmol/g carboxylate content resulted high level of water retention (13.4 g/g fiber) Cellulose nanofibers were used in cementitious mixtures. CNF with carboxyl groups resulted in better flow control in wet cement paste and reduced the crack growth in concrete.

Effects of Mg-based Alkaline Peroxide Bleaching on Physical Properties of Poplar Bleached Chemi-thermomechanical Pulp and Its Influence Mechanism

Effects of Mg-based Alkaline Peroxide Bleaching on Physical Properties of Poplar Bleached Chemi-thermomechanical Pulp and Its Influence Mechanism

Online measurement of bulk, tensile, brightness, and ovendry content of bleached chemithermomechanical pulp using visible and near infrared spectroscopy

Current pulp mill practice to determine the pulp properties of bleached chemithermomechanical pulp (BCTMP) is to prepare and test handsheets for properties of interest. While the use of handsheets is well established, tests require well trained technical staff and introduce a significant lag before test results can be acted upon. In this report, a prototype online visible and near infrared (Vis-NIR) sensor that complements handsheet testing was trialed for 16 months at a BCTMP mill. The system consists of a cabinet located near a probe installed on a conveyor belt between a slab press and a bale press. When a bale stops on the conveyor belt, the probe rises and comes into contact with the bale, taking a spectral measurement and predicting its bulk, tensile strength, brightness, and ovendry (o.d.) content. The data presented here covers a period of 100 days of real-time measurements that correlated with laboratory tests with an R2 of 0.88 for bulk, 0.87 for tensile, and 0.92 for brightness. Bulk, tensile strength, and brightness measurements had root mean square error of prediction (RMSEP) values of 0.19 cm3/g, 3.994 Nm/g, and 0.96 brightness points, respectively. Ovendry content measurements trended with the mill’s existing online moisture measurement system and had an R2 of 0.36 and an RMSEP value of 1.04%. The quality of the correlation for o.d. content was substantially impacted because of difficulties with synchronizing the time stamps between the mill’s existing online measurements and the online system reported here. The online Vis-NIR sensor provides information in real time and has the potential to be used to reach target grade properties more quickly, assist in the identification of inefficient chemical dousing, reduce the effect of operator bias during testing, allow for the prioritizing of laboratory tests, and improve segregation of final products according to customer needs. However, further development would be necessary to use these measurements as part of a process control strategy.

Iso-concentration hydrogen peroxide bleaching of poplar chemi-thermomechanical pulp

Maintaining a constant chemical concentration (Iso-concentration, IC) has been found to be an effective method to improve peroxide bleaching efficiency for chemi-thermomechanical pulp (CTMP). In this study, the mechanism of IC bleaching was investigated. The concentrations of H 2 O 2 and total alkali in IC bleaching were monitored and compared with those in conventional bleaching processes. Control experiments without pulp were carried out to explore the effects of bleaching additives on H 2 O 2 decomposition. The results showed that the concentrations of H 2 O 2 and the total alkali at the early and later stages of IC bleaching were relatively low and high, respectively; thus, undesired decomposition of H 2 O 2 was inhibited, and brightness was improved. Moreover, the stabilizer played an important role in inhibiting the undesired H 2 O 2 decomposition. This may explain why high bleaching efficiency was achieved in IC bleaching. These findings would provide valuable insight for the production of high-brightness bleached chemi-thermomechanical pulp (BCTMP).

Modeling and prediction of methanol air release from bleached chemi-thermo mechanical pulp board.

This paper reports on the modeling, prediction and evaluation approaches of methanol release from bleached chemi-thermo mechanical pulp (BCTMP) board during storage. A pseudo-first order desorption kinetics model of methanol release was established for describing the desorption behavior of methanol from BCTMP, i.e., , in which the desorption constant (K) and rate constant (kdes) were well described by van't Hoff and Arrhenius equations. Based on the simulation experiments at various temperatures, the desorption activation energy of methanol and its adsorption enthalpy is calculated and is 53.7 and −86.2 kJ mol−1 K−1, respectively. With the developed model, the risk of methanol release for the storage of BCTMP board can be examined by either the time-dependent kinetics model or a two-step thermodynamic approach using the equilibrium concentration of methanol in indoor air. This paper provides a valuable tool to assess the risk of methanol release for the paper industry and related warehouse departments.

Fibrillation of Aspen by Alkaline Cold Pre-treatment and Vibration Milling

In this article an attempt to fibrillate aspen bleached chemi-thermo mechanical pulp (BCTMP) fibre in an environmentally friendly way is reported. The effects of various NaOH, KOH, urea and ethanol aqueous solutions at lowered temperature were tested for pre-treatment. The pre-treatment was followed by vibration milling aiming to peel off outer cell wall layers and to fibrillate S2 layer of the aspen wood fibre. The effects of the treatments were evaluated by scanning electron microscopy (SEM). The results show that it is possible to fibrillate BCTMP aspen fibres by using alkaline aqueous solutions at low temperatures followed by a mechanical treatment. A strong dependence on fibrillation of cellulose on temperature, time and alkali concentration was established. DOI: http://dx.doi.org/10.5755/j01.ms.22.3.7412

Characteristics of high yield pulp fibers by xylanase treatment

The effects of xylanase treatment on the fiber surface properties of high yield pulp (chemithermomechanical pulp, alkaline peroxide mechanical pulp, and bleached chemithermomechanical pulp) were studied. Fibers surface composition and surface structure were investigated by X-ray photoelectron spectroscopy and scanning electron microscopy, respectively. The former demonstrated an increase in the atomic oxygen to carbon ratio, a decrease in the lignin content, and variation in the C1s on the fiber surface of enzymatically treated samples. An enrichment of a large proportion of open and fibrillated fibers was visualized by the latter, resulting in an improvement in the pulp’s physical strength-related properties. Surface modification using enzymatic treatments allow for improved fiber surface properties to obtain new products through sustainable technologies.

상이한 몰 비율의 LB 공융용매 처리에 따른 BCTMP 섬유 및 수초지 특성의 변화

ABSTRACT This study was conducted to investigate the effects of deep eutectic solvent (DES) treat-ment on BCTMP fibers and handsheets properties. DES was prepared using lactic acid and betaine (LB), and the molar ratio of these two components mixtures was controlled to 2:1 (LB 2:1) and 5:1 (LB 5:1). As results, 2% of BCTMP pulp (o.d. weight) was extracted when it was treated by LB 5:1 at 50℃ for 12 hours, stirring constantly at 120 rpm. In contrast, lignin was not extracted when BCTMP was mildly treated by the LB DES mixed with 50% of distilled water at the reacting condition of temperature 60℃ for 2 hours using water bath. These results indicate that conditioned water content and adequate reaction time are needed to achieve effective extraction of lignin. It was also found that stiffening of cellulose fiber due to the mild treatment of LB DES to BCTMP fiber leads to the increase of paper bulk without the loss of strength.Keywords: Deep eutectic solvent, LB (lactic acid and betaine), bleached chemithermome-chanical pulp, fiber properties, handsheet properties

Improving the hydrogen peroxide bleaching efficiency of aspen chemithermomechanical pulp by using chitosan

The presence of transition metals during the hydrogen peroxide bleaching of pulp results in the decomposition of hydrogen peroxide, which decreases the bleaching efficiency. In this study, chitosans were used as peroxide stabilizer in the alkaline hydrogen peroxide bleaching of aspen chemithermomechanical pulp (CTMP). The results showed that the brightness of the bleached CTMP increased 1.5% ISO by addition of 0.1% chitosan with 95% degree of deacetylation during peroxide bleaching. Transition metals in the form of ions or metal colloid particles, such as iron, copper and manganese, could be adsorbed by chitosans. Chitosans could inhibit the decomposition of hydrogen peroxide catalyzed by different transition metals under alkaline conditions. The ability of chitosans to inhibit peroxide decomposition depended on the type of transition metals, chitosan concentration and degree of deacetylation applied. The addition of chitosan slightly reduced the concentration of the hydroxyl radical formed during the hydrogen peroxide bleaching of aspen CTMP.

Stabilization of Potentially Sticky Substances in Pulp Mill Process Water with Polysaccharides

Characterization of the dissolved and colloidal substances (DCS) in the process water of a bleached chemithermomechanical pulp (BCTMP) production line showed that the major lipophilic substances (wood resins) were dehydroabietic acid, linoleic acid, oleic acid, and palmitic acid. Model compound experiments indicated that polysaccharides contained in DCS had significant effects on the stability of the system. Effects of neutral and acidic polysaccharides on the stability of wood resins (model resin acid R and fatty acid O) in the presence of metal ions were then investigated. No calcium-induced aggregation occurred when the concentration ratio of added neutral polysaccharide to R and O exceeded 0.2 and 1.0, respectively. Acidic polysaccharide could further degrade the stability of resin dispersions in the presence of calcium ions and yet have a positive effect in the presence of only sodium ions.