桉本化机浆的傅里叶变换红外光谱分析

用傅里叶变换红外光谱法对桉木中各组分在碱性亚钠法化机浆预处理及漂白过程中的化学变化进行了研究。结果表明木材在处理过程中存在脱乙酰基作用；木素的烷基芳基醚键受到破坏；纸浆中纤维素的结晶度指数下降；随预处理时ＮａＯＨ用量的增加，本素中形成了新的共轭羰基和醌型结构，它们使纸浆白度下降。同时对不同纸浆在漂白过程中的变化进行了研究，对影响纸浆白度的因素进行了分析     

Modification of hardwood dissolving pulp with purifiedTrichoderma reesei cellulases

Hardwood dissolving pulp was treated with purified Trichoderma reesei endoglucanases and cellobiohydrolases. Endoglucanases were more efficient in hydrolysing pulp carbohydrates than were the cellobiohydrolases at the same protein dosage. Endoglucanases also lowered the viscosity and improved the alkaline solubility more dramatically. There was a clear correlation between the alkaline solubility and viscosity, and therefore the solubility could only be improved by lowering the viscosity of the pulp. At the same degree of cellulose degradation, endoglucanase II was found to be most effective in reducing the viscosity and thus improving the solubility. Cellobiohydrolases had a less pronounced effect on the viscosity or solubility.     

Characterisation of dissolving pulp using designed process variables, NIR and NMR spectroscopy, and multivariate data analysis

Two processability variables, filter clogging and alkali resistance, were measured in a series of laboratorycooked viscose pulps. The pulps were also characterised by ¹³CCP/MAS solid state nuclear magnetic resonance (NMR) and near infrared (NIR) spectroscopy. Partial least squares (PLS) regression was used to investigate the information provided by the spectroscopic methods with respect to the processability measurements. The study showed that the alkali resistance, R18, of the pulp and the filter clogging value, Kw, of the laboratoryprepared viscose can be modelled by NIR and multivariate data analysis (MVA). The alkali resistance, R18, of the pulp can also be calculated by NMR and partial least squares (PLS) regression. Analysis of the loading values in the PLS model showed that pulps with high alkali resistance have higher crystallinity than pulps with low alkali resistance. Analysis of variables of the cooking conditions showed that the chemical charge (Na₂O) and pH should be kept low to give high alkali resistance, whereas high Na₂O gives low filter clogging values.     

Surface characterization of unbleached kraft pulps by means of ESCA

The effect of digestion conditions (amount of effective alkali, digestion time) on the surface compositions of unbleached softwood (Pinus sylvestris) kraft pulp has been investigated by electron spectroscopy for chemical analysis (ESCA). The quantities monitored were the angular dependence of the total O/C ratio, the relative amounts of carbons in different states of oxidation and the adsorption of Al and Ca ions to the carboxyl groups in the surface. Examination of the angular dependence of ESCA intensities shows that the concentration of alkyl carbon is high in a very thin surface layer and that it decreases linearly with decreasing kappa number. The concentration of alkyl carbon is decreased by extraction of the fibres with dichloromethane, but the amount remaining in the surface after extraction still decreases linearly with decreasing kappa number (i.e. it decreases with increasing digestion time). It is suggested that the observed enrichment of alkyl carbon in the outermost surface layers most probably is due to reprecipitation of lignin. In pulp that has not been extracted, there is also strong enrichment of extractives in the surface. This amount increases with increasing effective alkali but is relatively independent of digestion time. ESCA analysis of the Al and Ca bound to the carboxyl groups shows that the amount depends on digestion time; the results are consistent with the notion that the reprecipitated lignin contains carboxyl groups.     

Production and characterization ofPhanerochaete chrysosporium lignin peroxidases for pulp bleaching

The production of lignin peroxidase fromPhanerochaete chrysosporium was studied using immobilized mycelia in nylon-web cubes in semicontinuous fermentation using glucose pulses or ammonium tartrate pulses. Consistent enzyme production was achieved when glucose pulses were used, leading to an average activity of 253 U/L. The crude enzyme was added to eucalyptus kraft pulp before conventional and ECF bleaching sequences. Optimization of the enzymatic pretreatment led to the following operational conditions: enzyme load of 2 U/g of pulp, hydrogen peroxide addition rate of 10 ppm/h, and reaction time of 60 min. Pulp final characteristics were dependent on the chemical treatment sequence that followed enzymatic pretreatment. The chief advantage of enzymatic pretreatment was pulp viscosity preservation, which was observed in most of the experiments carried out with seven different chemical treatment sequences     

Surface properties of CTMP fibers modified with xylans

This study investigated the effect of modification with xylan on the surface properties of chemithermomechanical pulp (CTMP) from spruce. The surface modifications were carried out by controlled sorption of birch xylan from solution at high temperature and high pH. Several different analysis techniques were used to study the effects on fiber surface composition and morphology. The ESCA technique showed a reduction in the amount of carbons not bound to oxygen in the C(1s) resolved peak after treatment. Variations in surface topography between untreated samples and samples with xylan were studied with SEM and AFM in the tapping mode. Scanning electron micrographs show micrometersized xylan particle structures spread over the fiber surfaces. AFM images reveal differences in the fine structure of fibers. The modified fibers exhibit a nanometersized, bumplike morphology not seen on the untreated fibers. The wetting properties of single fibers were determined with the Wilhelmy plate technique and the water sorption of CTMP paper sheets was studied using a dynamic contactangle tester. The surface modification of CTMP with xylan significantly decreased the advancing contact angle of single fibers and also improved the water sorption of sheets.     

Grafting of acrylamide onto cellulosic fibers via dielectric-barrier discharge

Fully bleached kraft pulp (BKP) and thermomechanical pulp (TMP) fibers were grafted with acrylamide via dielectric-barrier discharge treatment at various treatment dosages. The results indicate that increased dielectric-barrier discharge treatment leads to the increased polymerization and incorporation of acrylamide onto fiber surfaces. Greater incorporation of poly(acrylamide) occurs on the BKP fibers than the TMP at the same treatment conditions. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and scanning electron microscopy (SEM) indicate that dielectric-barrier discharge initiated modifications to fiber surface topo-chemistry occur across the fiber such that the sheet is randomly peppered with modified areas; however, it occurs in patches on individual fibers as opposed to occurring as an evenly distributed thin film. SEM and elemental analysis also showed that the incorporation of acrylamide onto the fiber surface increases with increased treatment dosages.     

Effect of pulp composition on the characteristics of residuals in CMC made from such pulps

Four different spruce sulphite pulp samples were used for the preparation of carboxymethylcellulose (CMC). The characteristics of the unreacted fibre and particle residuals obtained in the CMC-preparation were used to establish a correlation between the hemicellulose in the pulp and the intrinsic viscosity, i.e.,␣cellulose chain length and the occurence of unreacted residuals. It was shown that the residual particles in the CMC consisted of fibres, fibre fractions and gel particles of different degrees of substitution. The results suggested that pulps with long cellulose chains, i.e., pulps with high intrinsic viscosities, resulted in particles that were more substituted and more swollen. These pulps also resulted in more substituted hemicelluloses in the CMC and more substituted residuals. It was also suggested that galactoglucomannan in the cellulose pulps is favourable for the swelling which results in more substituted hemicelluloses in the CMC and more swollen residuals. The amount of residuals was influenced mainly by the characteristics of the cellulose in the pulp. It is therefore believed that a combination of high viscosity and a suitable combination of hemicelluloses is the most favourable way of eliminating the occurrence of undissolved residuals in CMC.     

The influence of fibre wall thickness on the undissolved residuals in CMC solutions

An industrial calcium sulfite pulp was fractionated in a hydrocyclone to four fractions that differed in dimensions and composition due to differences in density. The intention was to investigate whether the fibre dimensions had any influence on the properties of carboxymethyl cellulose (CMC) produced from the fractions and especially how the properties of the unreacted material differed. It was surprisingly found that the fraction containing thin-walled fibres gave CMC and dissolved residuals in the CMC-solution that had the lowest degree of substitution (DS). It was therefore believed that the thin-walled fibres were collapsed and more closely bound in the fibre network after drying of the pulp and that this impeded the chemical diffusion in the subsequent CMC-process, i.e. the diffusion of the CMC-chemicals into the cell wall was slower. There was thus a correlation between thinner fibres and a lower degree of substitution for CMC made from such fibres. It was also found that tick-walled fibres had a higher degree of substitution than the thin-walled fibres but that the highest degree of substitution was obtained if a mixture of thin- and thick-walled fibres were used.     

麦草浆黑液石灰法除硅试验研究

根据麦草浆黑液石灰法除硅的原理,通过试验研究证实,稀黑液蒸发浓缩后,加入除硅剂Ca（OH）2并充分混合,在一定温度下进行灼烧反应,无需进一步苛化,除硅率和碱回收率便可得到良好的效果,使黑液硅含量降低95%以上,碱回收率也可达到95%左右,大大缓解了碱回收工艺流程中的硅积累现象。