Chemimechanical Pulp Research Articles

Effect of Partial Pre-Extraction of Hemicelluloses on the Properties of Pinus radiata Chemimechanical Pulps

Extraction of hemicelluloses prior to pulping and conversion of the extracted hemicelluloses to other bioproducts could provide additional revenue to traditional pulp and paper industries. The effect of hemicelluloses pre-extraction with a hydrothermal (HT) process on Pinus radiata chemimechanical pulp (CMP) properties was investigated in this study. The HT extraction resulted in a release of 7% to 58% of the initial amount of hemicelluloses from the wood. The extraction yield increased with temperature and extraction time. This hemicellulosic fraction was in the form of low molar mass oligomers with molecular weights varying from 1.5 to 100 kDa. Compared with the control (unextracted) CMP pulp, the HT pre-extraction significantly reduced the refining energy to obtain a given fibrillation degree (freeness). The pulp yield with the HT/CMP process was in the range of 56% to 75%. Fiber properties of the pulps from pre-extracted wood, such as fiber length, were reduced, while increases in fiber width, fines content, fiber coarseness, and kink index were observed in comparison with the control pulps. The strength properties of CMP pulps decreased with increasing amounts of hemicellulose removal during the stage prior to pulping.

High-energy electron irradiation of annual plants (bagasse) for an efficient production of chemi-mechanical pulp fibers

Abstract The paper industry is one of the largest consumers of energy and energy consumption has been increased several times in last few decades. Bagasse chemical pulping has very low yield about 45–55% and also generates high pollution load in the effluent as compared to mechanical pulping, g. Thermo-mechanical pulp (TMP). On the other hand,-->e.g. thermo-mechanical pulp (TMP). On the other hand, the specific energy consumption is very high for TMP pulps. ETMP (Energy efficient Thermo-Mechanical Pulping) or ECTMP (Energy efficient Chemi-Thermo Mechanical Pulping) is an innovative idea for reducing the energy demand in TMP refining. In the present investigation, energy efficient mechanical pulping potential of bagasse was studied using TMP, CTMP and ECTMP pulping methodology with electron irradiation pretreatment. It is evident from the results that more than 50% energy saving potential of irradiation pre-treatment was achieved.

Modifying the Refining Energy Consumption of Chemi-Mechanical Pulping with NaOH-Thiourea-Urea Aqueous Solution

To reduce the refining energy consumption of chemi-mechanical pulping, treatment with NaOH-thiourea-urea aqueous solution was studied in this work. By means of single-factor experiments, the effects of alkali dosage, soaking time, and freezing time were evaluated. It was found that the optimal conditions were an alkali dosage of 8%, soaking time of 45 min, and freezing time of 105 min. The results revealed that refining energy consumption could be reduced by approximately 40% under optimal conditions compared with that of alkaline peroxide mechanical pulp, while other pulping or paper-making properties were similar. There were no significant effects on the structure of the functional groups, the crystalline region of the pulp, or the whole structure of the treated wood chips. However, damage to single wood fibers on the chips treated in NaOH-thiourea-urea aqueous solution was more obvious.

Chemi-mechanical Pulping of Durian Rinds

The physical, optical and mechanical characteristics of pulp and paper made from waste durian rinds as an alternative raw material for papermaking were investigated according to TAPPI and MS ISO standards. The durian rinds pulp was produced through chemi-mechanical pulping (CMP). Naturally dried durian rinds were treated with 10% Sodium Hydroxide (NaOH) based on oven dry (o.d) weight of durian rinds in room temperature for 2hours and pulped by the refiner mechanical pulping (RMP) process. Experimental results show that durian rinds have great potential characteristics as newly explored non-wood based raw material for pulp and paper industry.

The effect of using willow wood on the optical and mechanical properties of newsprint paper obtained from chemi-mechanical pulp

In this study, the effect of mixing willow wood species with other wood species used in Mazandaran wood and paper industry on the optical and mechanical properties of newsprint paper made from chemi-mechanical pulp (CMP) was investigated. CMP pulp was made under condition of efficiency of 85 %, cooking time of 60 min, temperature of 170° C, and L:W = 7, sulfite percentage of 20 % based on the dry weight of the willow wood species in 6 levels. After handmade papers (60 g/cm2, gsm) were prepared, optical and mechanical properties of papers were evaluated. Results showed that the best optical properties were related to papers obtained from the factory pulps (control pulp), and only the opacity of papers obtained from willow paper pulp mixed with factory pulps has been in acceptable level (45:55, 45 % willow pulp to 55 % of the factory pulp). The best strength properties were observed in the incorporation of 100 % factory CMP pulp and in second priority 60:40 mixture (include 60 % of willow pulp with 40 % of factory CMP pulp). Due to the importance of strength properties compared to the optical properties in newsprint paper, incorporation of 60 % of willow pulp with 40 % of factory CMP pulp is suggested for newsprint paper.

Properties of Chemi-Mechanical Pulp Filled with Nanofibrillated and Microcrystalline Cellulose

Properties of Chemi-Mechanical Pulp Filled with Nanofibrillated and Microcrystalline Cellulose

Tear and tensile strength development of PGW and CTMP pulps mixed with PLA or viscose fibres

Abstract The objective was to evaluate the effects on paper properties when replacing a minor share of wood fibre by synthetic fibre. The aim was to increase tear strength and stretch while minimizing the loss of tensile strength in paper consisting of mechanical pulp. Tested synthetic fibres included PLA and viscose fibres mixed with mechanical or chemi-mechanical pulp. Even at relatively low proportions, the synthetic fibres contributed to a significant increase of tear strength in the wood fibre based papers. With the highest tested proportion (20%) the increase of tear index in PGW based stock was 243% with PLA and 177% with viscose fibre. However, a simultaneous decrease in tensile strength and tensile stiffness was observed. The stretch at break remained unchanged. Thickness reduction of the synthetic fibres resulted in an increase of tear strength. The effect is due to the high fibre length of synthetic fibres, producing mechanically well entangled networks, coupled with the high enough strength of the synthetic fibres.

Hydrogen Peroxide Bleaching of Canola Straw Chemimechanical Pulp

Canola straw can be used as a raw material for the production of chemimechanical pulp (CMP). In this work, chemimechanical pulp was first produced from canola straw, and then the bleaching performance of the produced chemimechanical pulp was investigated under different conditions (dosages of NaOH and Na2SO3, time, and temperature). The results showed that the yield of chemical pretreatment in the CMP process varied between 57.6% and 64.9%, while the total yield of the process was between 54.1% and 61.9%. Subsequently, the CMP pulp produced via applying 4% NaOH and 8% Na2SO3 at 145 °C for 15 min was bleached with H2O2. The results showed that pulps bleached via applying one stage of 3% H2O2, 3% NaOH, 6% sodium silicate, 0.5% MgSO4, and 0.3% DTPA for 150 min possessed the highest brightness of 60.8% ISO, which is suitable for container board production.

Effects of Weed Control and Fertilization on Wood and Chemi-mechanical Pulp Properties of a Populus deltoides Clone

Weed control and fertilization usually lead to an increase in the growth rate of trees and, consequently, to a possible modification of the quality of the wood and its end products. The effect of weed control and fertilization practices were determined on tree growth parameters, wood density, fiber weight, fiber length, and chemical wood composition, as well as the chemi-mechanical pulp properties, for 8-year-old Populus deltoides `Delta Gold´ grown in Argentina. Four treatments belonging to a randomized complete block design trial were analysed: no weeding after planting (C), mechanical weed control (M), chemimechanical weed control (CHM), and fertilized + chemimechanical weed control (CHM-F). Soda-sulfite chemi-mechanical pulps were produced from said trees. Handsheets were prepared from the pulps, and their physical, mechanical, and optical properties were determined following international standards. Several wood and pulp properties were influenced by the studied silvicultural practices. In the context of this study, silvicultural treatments applied to Populus deltoides ‘Delta Gold’ (formerly ‘Stoneville 66’) trees can be applied to increase productivity (volume and fibrous output) without detrimental consequences to wood and pulp properties, except for a slight reduction in brightness.

Research on Preparation and Properities of Chemi-Mechanical Pulp from the Waste Poplar Wood

In this study, we prepared unbleached chemi-mechanical pulp from waste poplar wood using alkaline processing under normal atmospheric pressure. The influnce of alkaline dosage and time to fiber morphology and properties of the paper were discussed. The parameters of fiber including the length ,width and curl index were measured by FQA. The optimal dosage of NaOH and the optimal time of soaking period in the preparation of pulp using waste poplar wood were studied. The results showed that the optimal dosage of NaOH was 6% and the time of soaking period was one day. The performance of the handsheet made from the poplar wood under the pulping conditions are as follows: tensile strength index of 27 N·m/g, tear index of 0.51 mN·m2/g, burst index of 1.7 KPa·m2/g, folding strength of 16 times, ring crush strength index of 5.7 N.m/g, whiteness of 55.5 ISO, white opacity of 97%, paper absorption liquid rate of 0.32 mm/s.

Newsprint from NSSC Bagasse Pulp Mixed with Hardwood CMP Pulp and Bleached Softwood Kraft Pulp

In this work, the possibility of using neutral sulfite semi-chemical (NSSC) bagasse pulp mixed with hardwood chemimechanical pulp (CMP) and bleached softwood kraft pulp (BSKP) was investigated with the aim of reducing hardwood and BSKP consumption. The bagasse NSSC pulp had a digester yield of about 73% and was unbleached. It was refined by a PFI mill to 400 mL CSF, but in the case of the hardwood CMP and imported long fiber pulp, the final refined freeness were selected to be 350 and 500 mL CSF. Handsheets were made (60 gm-2), and their strength indices and optical properties were measured. Results of this research on a laboratory scale indicated that using bagasse NSSC pulp mixed with hardwood CMP to make newsprint with acceptable quality is possible, and this process will also noticeably reduce the consumption of imported long fiber pulp and wood for producing the grades of paper usually made from CMP.

Effects of dissolution of some lignocellulosic materials with ionic liquids as green solvents on mechanical and physical properties of composite films

In this study two imidazole-based ionic liquids (ILs), namely 1-butyl-3-methyl-1-imidazolium chloride ([BMIM]Cl) and 1,3-methyl imidazolium dimethyl sulfate ([DiMIM][MeSO4]), were used to dissolve ball-milled poplar wood (PW), chemi-mechanical pulp (CMP), and cotton linter (CEL). A set of comparative experiments was carried out, and physical and mechanical properties of the composite films from three different raw materials were determined by means of optical transparency (OT), scanning electron microscopy (SEM), water absorption (WA), thickness swelling (TS), water vapor permeability (WVP), and tensile strength (σb). The overall evaluation indicates the inability of [DiMIM][MeSO4] in complete dissolution of lignocellulosic materials, and sample treatment with this solvent did not lead to water soluble degradation products. However, dissolution trials using [BMIM]Cl were able to dissolve all used lignocellulosic materials by destroying inter and intramolecular hydrogen bonds between lignocelluloses. The OT, WA, TS, and σb of regenerated CEL films were much higher than those of CMP and PW composites. In addition, CEL film showed the lowest WVP compared to WF and CMP composite films. This work demonstrated a promising route for the preparation of biodegradable green cellulose composite films.

The Effects of H2O2 Bleaching and DTPA Spraying on the Brightness Stability of Hornbeam CMP Pulp following Accelerated Irradiation Aging

In this research, hornbeam chips were cooked under chemimechanical pulp (CMP) conditions, and the pulps were prepared at a yield level of 85%. The CMP pulps were separately bleached with hydrogen peroxide and sodium dithionite with and without treatment with DTPA. Then 60 gr/m2 handsheets were made. The goal was to determine whether complementary bleaching with sodium dithionite improves optical behavior of the handsheets. Following DTPA solution spraying on the surface of hand sheets, brightness, opacity, and yellowness were improved, and the K/S ratio and PC number were decreased. Among different samples and following optical aging, it was found that in long-term aging, DTPA spray has considerable effect on improving the stability of brightness and increasing the paper’s durability against optical deterioration.

Optimization of the Properties of Poplar and Willow Chemimechanical Pulps by a Mixture Design of Juvenile and Mature Wood

Forest plantations of Salicaceae (poplars and willows) in Argentina are mainly used for the manufacture of pulp for newsprint. The rapid growth of these species results in a decrease in rotation age, which increases the proportion of juvenile wood. The aim of this work was to define the proportions of juvenile wood (JW) and mature wood (MW) of these species that can optimize the mechanical and optical properties of chemimechanical pulps for newsprint production. A two-component mixture type experimental design was used with proportions (JW:MW) of 0:100%, 25:75%, 50:50%, 75:25%, and 100:0%. When the mechanical properties were optimized, the highest desirability function was obtained with a JW:MW ratio of 100:0%, and the optimal ratio for optical properties was 0:100%. The pattern of variation of mechanical properties can be attributed to the higher density of MW, whilst that of the optical properties can be attributed to the higher content of extractives in the JW.

Some Physical and Mechanical Properties of Uncatalysed Acetylated Paper

The objective of this study was to investigate the influence of acetylation on properties of paper made using the chemi-mechanical pulp (CMP) process. Industrial unbleached CMP pulp was provided (before and after refining), and paper handsheets were made. After drying, the specimens were acetylated on a heated cylinder at 120 °C, with acetic anhydride without catalyst. Physical and mechanical properties including water absorption, porosity, printability, brightness, D-folding, breaking length, tear resistance, and burst strength of samples were measured and compared between treated samples and the controls. The results showed that acetylation intensity was increased by increasing reaction time. Water absorption exhibited a significant reduction due to acetylation. Brightness, D-folding, and burst showed an increasing trend as a function of the degree of acetylation. Tear resistance was decreased by acetylation. The refining process improved acetylation and decreased porosity. The results indicated that most of the important factors were significantly influenced and improved by both acetylation and the refining process.

Thermomechanical pulping of novel Brazilian Eucalyptus hybrids

Abstract The importance of Eucalyptus wood as a sustainable resource is well established. Mechanical pulp production is an energy-intensive process, and methods for decreasing energy demand are needed. In the present article, the structure of Eucalyptus hybrids and the produced pulps from the hybrids were assessed in terms of energy consumption, technical properties, and fiber morphology. The defibration and fiber development were investigated by traditional thermomechanical pulping in laboratory scale. There was no clear difference in the extent of defibration and fibrillation among the hybrids, with the exception of one hybrid (U2xGL1). Guaiacyl lignin contents of more than 7.2% had a minor influence on energy consumption, and this finding is different from the results of previous studies on chemimechanical pulping processes. However, a low amount of guaiacyl lignin (6.1% based on wood) decreased the energy demand. This assessment is of major importance concerning the energy-saving defibration during thermomechanical pulping production.

Investigating the Possibility of Chemi-mechanical Pulping of Bagasse

Chemi-mechanical pulping was evaluated as a potential way to prepare sugarcane bagasse fibers for papermaking. Cellulose, lignin, ash, and extractives soluble in alcohol-acetone were measured as 55.75%, 20.5%, 1.85%, and 3.25%, respectively. Fiber length, diameter, lumen cavity, and cell wall thickness were measured as 1.59 mm, 20.96, 9.72, and 5.64 µm. The chemi-mechanical pulping conditions were selected as follows: three charging levels of 10, 15, and 20% sodium sulphite, and three pulping times of 20, 30, and 40 minutes after reaching the pulping temperature. Pulping temperature was held constant at 165 oC. Different pulping conditions resulted in pulp yields between 65.38 and 84.28%. The highest yield (84.28%) was obtained using a treatment combination of 20 minutes pulping time and 10% sodium sulphite. The lowest yield (65.38%) was related to 40 minutes pulping time and 20% sodium sulphite. Pulps were refined to 300 ± 25 mL CSF, 60 gm-2 handsheets were made, and then strength indices and optical properties of the handsheets were measured. The results showed that 20% sodium sulphite, 40 minutes pulping time, at 165 oC can be considered as the optimum pulping conditions for bagasse CMP pulping. Tensile, tear, and burst strength indices, as well as the opacity of this pulp were measured as 39.59 Nmg-1, 6.66 mNm2g-1, 2.1 KPa m2g-1, and 95.35%, respectively.

Improved refining properties of pulps pretreated with ionic liquids under mild conditions

Imidazolium-based ionic liquids (ILs), including 1-butyl-3-methylimidazolium chloride (BmimCl) and 1-allyl-3-methylimidazolium chloride (AmimCl), were used to improve the refining properties of pulps under mild conditions. Results showed that the macro appearance of pulps was virtually unchanged after pretreatment with ILs under mild conditions. In addition, chemical pulps pretreated with ILs are more suitable for pretreatment than chemimechanical pulps. Pretreatment with ILs facilitates the refining process by destroying hydrogen bonds, which exist extensively in fiber. At the same refining energy input, the Canada standard freeness (CSF) of refined pulp decreased with improved fiber quality. At identical CSF values, the energy consumed during refining significantly decreased because ILs pretreatment facilitated swelling and fibrillation. The viscosity of cellulose changed slightly after IL pretreatment. However, the crystallinity index and fines content decreased, and the micro appearance of the fiber surface changed. BmimCl has a stronger swelling influence on pulp than AmimCl under optimal conditions.

REVIEW: LIGHT-INDUCED YELLOWING OF LIGNOCELLULOSIC PULPS – MECHANISMS AND PREVENTIVE METHODS

This review will focus on recent progress regarding the mechanisms of light-induced discoloration of mechanical and chemimechanical pulps and on the proposed preventive treatments. It is evident that the mechanisms behind photoyellowing of lignin-rich pulps are complex and that several types of reaction pathways may coexist. Photoyellowing proceeds via one initial fast phase and a slower following phase. The fast phase has been ascribed to oxidation of free phenolic groups and/or hydroquinones and catechols to photoproducts of mainly quinonoid character. A multitude of reactions involving several lignin subunits are possible. Important intermediates are phenoxyl radicals, and to some extent ketyl radicals. The importance of the phenacyl aryl ether pathway might be more important than previously thought, even though the original content of such groups is low in lignin. Even though many preventive methods against photoyellowing have been suggested, no cost-efficient treatment is available to hinder photoreversion of lignin-containing paper permanently. Suggested methods for stabilization include chemical modification (etherification and esterification), coating the paper product, addition of radical scavengers, excited state quenchers, or ultraviolet absorbing compounds.

Mg(OH)2-BASED HYDROGEN PEROXIDE BLEACHING OF CMP PULPS AT HIGH CONSISTENCY

The objective of this study was to investigate the bleaching performance of a Mg(OH)2-based hydrogen peroxide process at a high consistency. In this work, an industrially produced chemimechanical pulp (CMP) was bleached via Mg(OH)2- or NaOH-based hydrogen peroxide processes at 10% and 25% consistencies. The results showed that the pulp bleached under the conditions of 1.5% Mg(OH)2 and 3% H2O2 at 25% consistency had a similar brightness to, a lower yellowness index, and a higher opacity than the pulp produced under the conditions of 2.1% NaOH, 3% Na2SiO3, and 3% H2O2 at the same consistency. The temperature (70 oC) and time (150 min) of the bleaching were the same for both processes. Under the conditions stated above, the Mg(OH)2-based process had a higher yield than the NaOH-based process did. The bleaching effluent of the Mg(OH)2-based process had a higher residual H2O2, but a lower Chemical Oxygen Demand (COD) load and turbidity, compared with that of the NaOH-based process. However, the strength properties and water retention value (WRV) of the pulp bleached via the Mg(OH)2-based process were lower, while its bulk was higher than those of the pulp bleached via the NaOH-based process.