The effect of Trichoderma reesei cellulases and hemicellulases on the paper technical properties of never-dried bleached kraft pulp

Four purified cellulases, a xylanase and mannanase from Trichoderma reesei were used to treat never-dried bleached pine kraft pulp prior to refining, and the effects on pulp properties were evaluated. The enzymatic treatments hydrolysed up to 0.8% of pulp dry weight. The results demonstrated that the individual cellulases have profoundly different modes of action in modifying pulp carbohydrates. This is especially clear when comparing their effects at the same level of hydrolysis. Pretreatment with cellobiohydrolases I (CBH I) and II (CBH II) had virtually no effect on the development of pulp properties during refining, except for a slight decrease in strength properties. On the contrary, endoglucanase I (EG I) and endoglucanase II (EG II) improved the beatability of the pulp as measured by Schopper--Riegler value, sheet density and Gurley air resistance. Of the endoglucanases, EG II was most effective in improving the beating response. The combinations of CBH I with EG I and EG II had similar effects on the pulp properties as the endoglucanases alone, although the amount of hydrolysed cellulose was increased. Pretreatments with xylanase or mannanase did not appear to modify the pulp properties. The same enzyme treatments which improved the beatability, however, slightly impaired the pulp strength, especially tear index at the enzyme dosages used. When compared at a given level of cellulose hydrolysis, the negative effect of EG II on strength properties was more pronounced compared with EG I. Thus, the exploitation of cellulases for fibre treatments requires careful optimization of both enzyme composition and dosage. Since the endoglucanases had no positive effect on the development of tensile strength, it is suggested that the explanation for the increased beating response is increased fibre breakage and formation of fines, rather than improved flexibilization. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of the properties of chemical cellulose pulps

The literature related to differences between chemical cellulose pulps produced by different pulping processes has been reviewed. Kraft pulps tend to be stronger, particularly in tear strength, while sulfite pulps hydrate and beat more readily. Organosolv pulps tend to mirror the properties of sulfite more than those of kraft pulps. A number of theories have been offered to explain the different properties of the chemical pulps; however, none has been universally accepted. It may be that acidic processes develop weak points in the fibers which are magnified in tear strength losses since, at a constant tensile strength, a 10% loss in fiber strength can lead to a 25–30% loss in tear strength. The effects of acidic pulping may also be magnified in greater fiber breakage and damage in the subsequent refining stages. However, strength improvements for inferior pulps can be realized through post-chemical treatments. Caustic treatments appear to give the greatest improvements, presumably due to increases in acidic group content which results in enhanced swelling properties, and possible subtle reorientation of cell wall polymers. The strength of hornified, recycled fibers can also be enhanced with such treatments, although simple beating will restore considerable strength, but at the expense of drainage rates. It is clear that the processes are complex and involve both the chemistry and physics of the fibers and how these attributes combine to affect the subsequent beating of the fibers for bonding and strength development.     

Composition Profiles of Dental Enamel Studied by X-Ray Photoelectron Spectroscopy (ESCA)

Abstract

The surfaces of both normal and fluoride treated human dental enamel were examined with x-ray photoelectron spectroscopy (ESCA). Using argon-ion etching to remove thin layers of enamel, subsurface layers were also analyzed. The resulting composition-depth profile showed that stannous fluoride produced a subsurface layer containing both tin and fluoride whereas fluorine was absent from the surface layer. Acid fluoride treatments, however, converted the surface to calcium fluoride which steadily decreased in concentration with depth.     

Mutagenicity of Tectona grandis Wood Extracts and Their Ability to Improve Carbohydrate Yield for Kraft Cooking Eucalyptus Wood

Considering the toxicity of the impurities of synthesized anthraquinone, this study clarified new catalytic compounds for kraft cooking with improved carbohydrate yield and delignification and less mutagenicity, which are important for ensuring the safety of paper products in contact with food. The 2-methylanthraquinone contents of teak (Tectona grandis) woods were 0.18–0.21%. Acetone extracts containing 2-methylanthraquinone from Myanmar and Indonesia teak woods as additives improved lignin removal during kraft cooking of eucalyptus wood, which resulted in kappa numbers that were 2.2–6.0 points lower than the absence of additive. Myanmar extracts and 2-methylanthraquinone improved carbohydrate yield in pulps with 1.7–2.2% yield gains. Indonesia extracts contained more deoxylapachol and its isomer than 2-methylanthraquinone. The residual content of 2-methylanthraquinone in the kraft pulp was trace. Although Ames tests showed that the Indonesia and Myanmar extracts were mutagenic to Salmonella typhimurium, 2-methylanthraquinone was not. The kraft pulp obtained with the additives should be safe for food-packaging applications, and the addition of 0.03% 2-methylanthraquinone to kraft cooking saves forest resources and fossil energy in industries requiring increased pulp yield.     

Bleaching of kraft pulp with commercial xylanases

The perform ance of commercial xylanases in totally chlorine-free bleaching of kraft pulp from conifer was tested with Pulpzyme HC (Novo Nordisk) and Cartazyme NS-10 (Sandoz/Clariant), at 500 U/kg of dry pulp, respectively. The treatment with Pulpzyme (X_p) or Cartazyme (X_c) has been combined with stages of bleaching using: oxygen (O), sulfuric acid (A), and extraction with hydrogen peroxide (E_op). The following sequences have been tested: OXpAE_op, OXcAE_op, XpOAE_op, XcOAE_op and OAE_op, Kraft pulp bleached at the Klabin industrial plant using the sequence, CEH (chlorine, alkaline extreaction, and hypochlorination) was, used for comparison. The following average values were obtained: 1. Kappa number: OX_pAE_op, 4.8; OX_cAE_op, 4.9; XpOAE_op, 5.0; XcOAE_op, 4.9; OAE_op, 5.6, and CEH, 1.9; 2. Brightness (% ISO values): OX_pAE_op, 68.4; OX_cAE_op, 70.1; X_pOAE_op, 67.9; X_cOAE_op, 26.9; X_pOAE_op, 23.4; X_cOAE_op, 23.1; OAE_op, 25.4, and CEH, 25.2. Pulps that were treated with xylanases, before or affer the delignification with oxygen, have shown reduced kappa number and higher brightness than the pulp OAE_op, Enzyme treatment before delignification with oxygen reduces pulp viscosity. Brightness obtained for pulp produced with bleaching sequences containing the enzymatic treatment, when compared with the control, CEH, shows that the xylanases enhance the action of the bleaching agents.     

Upgrading of paper grade pulps to dissolving pulps by nitren extraction: yields,molecular and supramolecular structures of nitren extracted pulps

Different paper grade pulps were extracted with nitren in order to produce dissolving pulps and polymeric xylan. The yield and molecular structure of the extracted pulps were investigated by carbohydrate analysis and HPSEC combined with fluorescence labelling in order to additionally monitor the carbonyl and carboxyl group profiles of the pulps. The supramolecular structure of selected pulps were further studied by solid state ¹³C-CP/MAS-NMR and wide-angle X-ray scattering (WAXS). These supramolecular data of nitren extracted pulps were compared to samples extracted with NaOH and a conventional dissolving pulp in order to classify the properties of nitren extracted pulps. Nitren extraction results in selective xylan removal without noticeable degradation or oxidation of the cellulose fraction. The resulting dissolving pulps have high molar masses, a narrow molar mass distribution and the typical contents of carbonyl and carboxyl groups. The supramolecular structure of cellulose is less affected by nitren compared to strong NaOH, and the resultant dissolving pulps still have the cellulose I structure. All laboratories are members of the European polysaccharide network of excellence EPNOE.     

Efficient total halogen-free photochemical bleaching of kraft pulps using alkaline hydrogen peroxide

Total halogen-free bleaching of kraft pulps was conducted by an oxidative photochemical process at room temperature using alkaline hydrogen peroxide. Selection of an appropriate wavelength of light was crucial for effective bleaching and avoiding degradation of cellulose. The wavelength of the light has to be selected so that the light is absorbed only by the colored compounds in the pulps and not by the bleaching reagents or the pulp itself. When a long-wavelength black-light fluorescent lamp was used in combination with aqueous hydrogen peroxide solution at pH 11, the bleaching efficiency for hardwood and softwood kraft pulps reached the same level as that obtained by conventional two-stage elemental chlorine-free processes.     

Properties and treatments of pulps from recycled paper. Part II. Surface properties and crystallinity of fibers and fines

Surface properties of bleached kraft pulps were evaluated before and after recycling, and after a series of chemical treatments designed to improve and/or modify the pulp characteristics. The surface free energy characteristics of the pulps were determined using the Wilhelmy technique, and ESCA and ATR-FTIR methods were used to evaluate the chemical composition of the surfaces of the pulp fibers. In general rather small changes were noted at the fiber surfaces with recycling and chemical treatment. Recycling tended to increase the acid component and decrease the base component of the surface free energy of the pulps. This could result from exposure of carboxyl groups from hemicelluloses and/or from oxidized layers from the bleaching process. ESCA analyses also indicated increased carboxyl concentration at the surfaces of the recycled fibers. Although treatment with aqueous bases and organic solvents tended to increase the hydroxyl content on the surface of recycled pulps, the chemical treatments were not beneficial to pulp quality. AFM and SEM of fiber and fine surfaces of kraft pulps revealed that the fines fraction was altered to a much greater extent with recycling. Although recycled fibers appeared to have improved wettability, these small changes in the surface characteristics do not appear to play the dominant role in the characteristics of recycled pulps. Recycling did not change the crystallinity of whole pulps, but it increased the crystallinity of the fines fraction. The increase in the crystallinity of the fines fraction and the reduction in the water retention value (WRV) and the bulk carboxyl content (xylan) of the recycled pulps, as noted in Part I of this paper, appear to play the predominant role in determining the characteristics of recycled pulps. It appears that the loss of the hemicelluloses in the bulk of the fiber with recycling is much more important for internal fibrillation than the apparent small increase of hemicelluloses at the surface of recycled fibers.     

Surface Composition and Surface Energetics of Various Eucalypt Pulps

In this paper we report on our study of the surface chemical composition, surface energy and acid-base characteristics of plantation eucalypt pulps obtained using the kraft, neutral sulphite semichemical (NSSC) and cold soda processes. X-ray photoelectron spectroscopy (XPS) was used to quantify the surface coverages of extractives and lignin. Inverse gas chromatography (IGC) was used to analyse the dispersive component and the acid-base characteristics of the pulp samples. The pulp yield and the total lignin and extractives in the pulp increased in the sequences of kraft, NSSC and cold soda. The relative surface concentrations of extractives and lignin on the pulps (expressed in terms of the ratios of the pulp surface coverage to the total content of these materials in the pulp) did not increase in the same sequence. The relative surface concentrations of lignin and extractives on the kraft pulps were found to be distinctively higher than those of the NSSC and cold soda pulps. The dispersive components of the surface energy of all pulps were similar before extraction, but increased by different degrees after extraction, with that of the cold soda pulp showing the lowest degree of increase. The acid-base characteristics of the pulps were evaluated using the method of acceptor and donor constants described by Schultz and Lavielle and the method of work of adhesion described by Lundqvist and Ödberg. A comparison of these methods has been made. The acidity of all pulps was found to increase after extraction. The degree of increase in pulp acidity is negatively correlated with the surface lignin concentration on the pulps. The low relative acidity of the cold soda pulp is probably associated with its high surface lignin coverage. An experimental model was established to test this hypothesis.     

A comparative CP/MAS 13C-NMR study of cellulose structure in spruce wood and kraft pulp

CP/MAS ¹³C-NMR spectroscopy in combination with spectral fitting was used to study the supermolecular structure of the cellulose fibril in spruce wood and spruce kraft pulp. During pulping, structures contributing to inaccessible surfaces in the wood cellulose are converted to the cellulose I allomorph, that is, the degree of order is increased. This increase is also accompanied by a conversion of cellulose I to cellulose I. Cellulose from wood composed of different cell types, that is, compression wood, juvenile wood, earlywood, latewood and normal wood exhibited a similar supermolecular structure. Assignments were made for signals from hemicellulose which contribute significantly to the spectral C-4 region (80–86 ppm) in kraft pulp spectra but substantially less to the corresponding region in wood spectra.     

用ESCA谱仪研究氟共聚物F2314的共聚特性

由不同共聚比的偏二氟乙烯 (ＶＤＦ)和三氟氯乙烯 (ＣＴＦＥ)共聚合而形成的一系列共聚物体系在工业上有着广泛的应用。其中 ,未硫化的ＶＤＦ/ＣＴＦＥ共聚物 (俗称生胶 )常作为粘结剂。其中 ,氯原子只存在于单体ＣＴＦＥ形成的链段中 ,常用氯含量来表征ＶＤＦ/ＣＴＦＥ共聚物中共聚单体的链节比。但也发现氯含量相似的同一类型的ＶＤＦ/ＣＴＦＥ共聚物的溶解性上常存在较大的差异。影响共聚物溶解性的可能因素[1- 3] 为聚合度及共聚特性 ,包括链接方式等。前期的研究表明溶解性能差异较大的共聚物的聚合度没有明显的变化。本文采用ＥＳＣＡ…     

The influence of hemicellulose on fibril aggregation of kraft pulp fibres as revealed by FE-SEM and CP/MAS 13C-NMR

Three Norway spruce pulps were produced using different kraft pulping methods, in order to obtain large differences in cellulose and hemicellulose proportions at a similar lignin content. The hemicellulose content in the three pulps varied between 10% and 22%. The aim of the study was to evaluate the influence of cellulose and hemicellulose on fibre ultrastructure and correlate this with the differences observed in the mechanical properties between the pulps. The ultrastructure of the pulp fibres were studied using Field Emission Scanning Electron Microscopy (FE-SEM) and Solid-State Cross Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (CP/MAS ¹³C-NMR) in combination with spectral fitting. CP/MAS ¹³C-NMR measured the average bulk properties of the pulp fibres, while FE-SEM allowed for observations on the ultrastructure of fibre surfaces. The ultrastructure of the fibres varied with varying hemicellulose content. The pulp with a high hemicellulose content had a porous surface structure. In fibres with a low hemicellulose content, the fibril aggregates (macrofibrils) formed a much more compact surface structure. With CP/MAS ¹³C-NMR this change was reflected by an increase in average fibril aggregate width with decreasing hemicellulose content. Results from FE-SEM and CP/MAS ¹³C-NMR correlated well. The changes recorded in ultrastructure may explain the very different mechanical properties reported previously for pulps with different hemicellulose content.     

Sorption of dissolved galactoglucomannans and galactomannans to bleached kraft pulp

Sorption of mannans onto bleached kraft pulp (BKP) was investigated withreference to other interactions of mannans in mechanical pulping andpapermaking. O-Acetyl galactoglucomannans (GGM) isolated from thermomechanicalpulp (TMP), as well as enzymatically modified guar gum galactomannans (GM) wereused in the study. The results showed that deacetylation of TMP GGMs, alsooccurring during peroxide bleaching of TMP, dramatically increased thesorption.A higher sorption was also achieved after salt addition, while temperature hadno effect. Sorption of guar gum GMs onto BKP fibres was, on the other hand,quite unaffected by external conditions such as temperature, pH and saltaddition. The degree to which the pulp was beaten did not notablyinfluence the sorption either – only unbeaten pulp gave a clearly lower mannansorption. A lower number of galactose side groups, however, strongly affectedsorption – the lower the number of side groups, the higher the sorption.The molar mass did not seem to affect the rate of sorption to any higher extentat ambient temperature. At higher temperatures the rate of sorption of smallerGM polymers was, nevertheless, slightly increased. Low-molar-mass GMs alsosorbed at a higher rate onto unbeaten pulp compared to high-molar-mass mannans.GM sorption appeared to be virtually irreversible.     

Properties and treatments of pulps from recycled paper. Part I. Physical and chemical properties of pulps

The mechanical, physical, and chemical properties of recycled pulps were evaluated after a series of treatments designed to improve and/or modify the pulp characteristics. Tensile strength, bursting strength, and apparent density of the pulps decreased with recycling. However, the tear strength, in most cases, increased after the first recycle and then decreased after the second recycle. Carboxyl content and WRV of pulps also decreased with recycling. Chemical treatments did not increase the bonding ability of recycled pulps and, in most cases, decreased the physical properties of the pulps. Altering the physical state of the cellulose microstructure through additional swelling did not appear to be a significant factor for strength restoration. It may be that the hemicelluloses plan a greater role in recycling than originally thought.     

A simple and tailor‐made fabrication of porous silicon carbide from functionalized kraft pulp paper

Porous silicon carbide (SiC) materials were fabricated using the polymer‐derived ceramics method with kraft pulp papers (KPP) and a commercial polycarbosilane, the allylhydridopolycarbosilane (AHPCS), as starting materials. For this, KPP, propargylated KPP, or phosphorylated KPP were used to be impregnated by the AHPCS, with or without Karstedt catalyst. The pyrolysed materials were characterized at different stages, by using thermogravimetric analysis (TGA) coupled with mass spectrometry, X‐ray diffraction (XRD), and scanning electron microscopy (SEM). Depending on the nature of the initial template, various architectured SiC ceramics were successfully obtained with adjustable porosities. The key role of the previous functionalization of the papers was highlighted in terms of interactions at the interface between the polymer and the lignocellulosic handsheets. It led to either replica or sacrificial template methods. Thus, it was possible to tune the open porosity of the porous carbon and β‐SiC materials between 14.8% and 92.9%, with ceramic yields varying from 12% to 71%.     

Effect of unmodified kraft lignin concentration on the emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid to produce polymer hybrid latex

The introduction of non‐modified kraft LignoBoost® lignin (KL) to produce polymer hybrid latex has received much attention in recent years because it is derived from renewable resources. The focus of this work is to develop a polymer hybrid latex by emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid in the presence of different concentrations of KL furnished by the pulp and paper industry. The study intends to substitute a styrene in the system to understand the effect of non‐modified KL on the properties not only of the latexes, but also on the copolymers themselves. Each polymerization was carried out by shot‐process of tertbutyl hydroperoxide and sodium formaldehyde sulfoxylate as the redox system. The polymer latexes were characterized in relation to overall conversion, particle diameter, particle morphology, coagulum formation, surface tension, zeta potential, and atomic force microscopy. The polymers were evaluated through gel permeation chromatography, water absorption, and thermal properties. The results show that the addition of non‐modified KL results in inhibition of the polymerization and that KL acts as a colloid stabilizer. Small particles were generated in the initial stages of the polymerizations. The presence of the KL altered the color of the latexes; the increase in KL concentration resulted in increase in the absorption of water of the polymer films; the increase in KL concentration resulted in decrease of the molar mass of the copolymers.     

Controlled modification of poly(hydroxybutyrate) surfaces by a perfluorohexane plasma: ESCA and contact angle studies

Poly(hydroxybutyrate) films and inorganic glass slides were treated by cold plasma. The composition of the gas mixture of perfluorohexane and hydrogen was varied to obtain controlled surface coatings of different hydrophobicities. The analysis by weight variation, scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and contact angle measurements were used to evaluate the influence of the flow rate, composition, and the plasma power on the surface structure after the plasma deposition. High-resolution ESCA spectra were used to determine quantitatively the amount of different fluorine-containing species present in the plasma-deposited layers. Molecular structures and surface energies of deposited layers on polymer substrates were compared with those on inorganic substrates. In both cases a strong correlation was found between the surface free energy and the fluorine/carbon ratio as well as the oxygen/carbon ratio. Furthermore, samples with high carbon/fluorine ratios showed a high content of CF₂ and CF₃ groups. © 1993 John Wiley & Sons, Inc.     

Effect of Bacillus circulans D1 thermostable xylanase on biobleaching of eucalyptus kraft pulp

The alkalophilic Bacillus circulans D1 was isolated from decayed wood. It produced high levels of extracellular cellulase-free xylanase. The enzyme was thermally stable up to 60°C, with an optimal hydrolysis temperature of 70°C. It was stable over a wide pH range (5.5—10.5), with an optimum pH at 5.5 and 80% of its activity at pH 9.0. This cellulase-free xylanase preparation was used to biobleach kraft pulp. Enzymatic treatment of kraft pulp decreased chlorine dioxide use by 23 and 37% to obtain the same kappa number (κ number) and brightness, respectively. Separation on Sephadex G-50 isolated three fractions with xylanase activity with distinct molecular weights.     

Characterization and sources of extractable organochlorine in white sucker downstream from bleached kraft pulp mills

Organochlorine, obtained by extraction with hexane–acetone mixture (3?:?1) of fillets of white sucker (Catostomus commersoni) sampled downstream of pulp mills and in a reference river, was characterized by gel-permeation chromatography, transesterification, neutron activation analysis, and gas chromatography with halogen-sensitive detection. It was found that over 78% of the extractable organochlorine (EOCl) is of relatively high molecular weight (>～350). Chlorinated fatty acids account for 43–80% of EOCl in the high-molecular-weight portion, while chlorobenzenes, chlorinated pesticides, and polychlorinated biphenyls account for 4–55% of EOCl in the low-molecular-weight portion. Though undetectable in reference fish, three particular chlorinated fatty acids, i.e. threo-5,6-dichlorotetradecanoic, threo-7,8-dichlorohexadecanoic and threo-9,10-dichlorooctadecanoic acids, are characteristic of EOCl from fish collected downstream of bleached kraft pulp mills using chlorine-based bleaching, representing about 30% of total EOCl, of which threo-5,6-dichlorotetradecanoic acid alone accounts for 60–70%. It is thus evident that, among chlorinated compounds discharged from bleached kraft pulp mills, threo-9,10-dichlorooctadecanoic acid, presumably generated in chlorine-based bleaching processes, is the most bio-accumulative in fish and can be biodegraded by fish into dichlorohexadecanoic and dichlorotetradecanoic acids, presumably via β-oxidative metabolism. These three compounds were also identified in suspended solids isolated from biologically treated final effluent discharged from a bleached pulp mill using 50% ClO₂ substitution, thus confirming the effluent-related source for downstream fish. The finding also suggests that β-oxidation of dichlorooctadecanoic acid may also be operative in micro-organisms.     

Surface and morphological characterization of polysiloxane-block-polyimides

Two series of polysiloxane-block-polyimides were synthesized by the method of solution imidization of the polyamic acids prepared from the dianhydride/diamine combinations of 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA)/2,2-bis[4-(4-aminophenoxy) phenyl] propane (BAPP) (Series A) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA)/bis[4-(3-aminophenoxy) phenyl] sulfone (BAPSM) (Series B) with three kinds of w-diamino-poly(dimethylsiloxane) with different number-average molecular weight added as a part of diamine. These polysiloxane-block-polyimides, having various compositions and chain lengths of the polysiloxane segments, were subjected to solution casting to prepare their films, and their surface and interface properties were analyzed by contact angle, XPS, AFM, and SEM. It was found that the surface tension and surface topography were greatly influenced by the composition and molecular weight of the polysiloxane segments because of their surface enrichment, which was affected by the environment and substrate with which the copolyimides had contacted. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2239–2251, 1997