摘要:

Organosolv lignin fractions were used as substrate for further investigations on the effect of bleaching and photoyellowing on lignin. These lignins were extracted from spruce TMP, bleached TMP (BTMP) and bleached and yellowed TMP (YBTMP). Furthermore, lignin fractions from TMP were also directly submitted to bleaching conditions and lignin fractions from BTMP to irradiation in the solid state. These lignin samples were all analyzed by thioacidolysis and FT-IR spectroscopy. The bleaching did not substantially change the lignin polymer but considerably destroyed some chromophoric structures such as coniferaldehyde end-groups. On the other hand, the photoyellowing resulted in marked degradations of lignin, shown by a decrease in the amount of β-O-4 and β-1 interunit bonds and a substantial increase in vanillin and vanillic acid end-groups and in catechol units.

ISSN:0277-3813    

DOI:10.1080/02773819308020512

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

FT-IR spectroscopy was used to characterize chemically modified wood pulp and to judge the efficiency of different pulp modification processes. Treatment of wood pulp with aliphatic anhydrides was shown to be more effective in a polar solvent such as DMF compared to a non-polar one typified by xylene. The esterification of hydroxyl group associated with the cellulosic material was indicated by the characteristic absorption bands of the resulting cellulosic esters; the degree of hydroxyl conversion was determined by the ratio of peak intensity of hydroxyl and carbonyl stretching vibrations. The so-called “Infrared Acetyl Index” was shown to give a linear correlation with the gravimetrically determined anhydride uptake. Isocyanate modification of wood pulp yielded more complex infrared spectra, because of various secondary reactions of the reactive isocyanate component. Various aromatic isocyanates, used for chemical treatment of the wood pulp, led mainly to urethane formation, as evidenced by the spectra of the modified pulp. The presence of polyurea or urea as the main reaction product of aromatic isocyanates, postulated by a number of authors, could not be confirmed. Nevertheless, phenylisocyanate treatment, at high concentration of isocyanate and without purification of the modified pulp, led to the appearance of at least one more reaction product in the pulp spectra, which is presumed to be either triphenylisocyanurate, the trimerization product of phenylisocyanate, or carbanilide.

ISSN:0277-3813    

DOI:10.1080/02773819308020513

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Dioxane lignin isolated from a hardwood (birch,betula verrucosa) and milled wood lignin isolated from a softwood (black spruce,picea mariana) were subjected to a variety of selective reactions to modify some of their functional groups. All the lignins were then treated with 1, 3, 2-dioxaphospholanyl chloride (I) and the31P NMR spectra of the derivatives were recorded. Most of the31P NMR signals were assigned from the chemical shifts previously obtained from model compounds. The signals arising from derivatizing me labile protons in carbohydrates,erythroandthreoforms in β-O-4 structures, primary hydroxyls in a variety of lignin structures, syringyl and guaiacyl phenolic hydroxyls and those of carboxylic acids were assigned. Thealphabenzylic hydroxyls in β-O-4 structures within birch lignin were less reactive toward alkylation than those in spruce lignin, consistent with the findings of previous workers; a difference attributable to the aryl part of the β-O-4 ether. The31P NMR spectroscopy of lignins derivatized with 1, 3, 2 dioxaphospholanyl chloride is thus shown to have considerable potential for the structural elucidation of lignins. This simple method is recommended for the rapid analysis of soluble lignins.

ISSN:0277-3813    

DOI:10.1080/02773819308020514

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The use of kenaf as a raw material for the preparation of ultra-high-yield pulp by applying conventional (CMP and CTMP) and non-conventional (explosion pulping) process conditions, has been investigated. Explosion pulping conditions used for kenaf pulping are actually the optimum conditions for aspen pulping. The effects of impregnation chemicals on explosion pulp properties are examined while the cooking time and temperature are kept constant at optimum level. Breaking length of kenaf explosion pulp is undoubtedly higher than that of simulated CMP and CTMP, even in the case of lower ionic content-Tear values of explosion pulp, CMP and CTMP are similar when the impregnation chemicals contain 1% NaOH in addition to 8% Na2S03. The relative specific refining energy requirements of explosion pulp, CMP and CTMP are greatly influenced by impregnation chemicals. Sulfonate content of explosion pulp depends on the chemical charge. Pulp yield, brightness and opacity decrease with the rise of the sulfonate content of pulp achieved by increasing the chemical charge or by adding NaOH along with Na2SO3. The kenaf explosion pulp can be bleached to 77% from an initial 57% level by using 3 to 4% H202in a peroxide bleaching process.

ISSN:0277-3813    

DOI:10.1080/02773819308020515

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Gel permeation chromatography of spent liquors from oxygen bleaching showed that cleavage of covalent linkages in the fiber was a prerequisite for the dissolution of the lignin. The reactions continued in the liquor phase. The cleavage was related to the oxidation of the lignin. With pulps pretreated with nitrogen dioxide an appreciable number of lignin linkages were cleaved also by the direct influence of the hydroxide ions on the nitrated lignin. In the alkaline medium the acidic sites in the fiber and in dissolved lignin fragments are ionized. Donnan-exclusion and an increased fiber swelling promote the transfer of the fragments into the liquor. Hydrophilic groups introduced into the lignin during oxygen bleaching promote the delignification.

ISSN:0277-3813    

DOI:10.1080/02773819308020516

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The decreases in kappa number of an unbleached alkaline hardwood pulp ofcarpinus betuluswhen performing dilute H2SO4hydrolysis at about 100°C, either after or before oxygen bleaching are the same. The main parameters of this acid hydrolysis are specified by studying the acidification of unbleached alkaline pulp suspensions at room temperature, and the extraction kinetics at temperatures in the range of 88°–110°C by following UV absorbance of the hydrolysis liquors.

ISSN:0277-3813    

DOI:10.1080/02773819308020517

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Retention performance of the polyethylene oxide (PEO)-phenolformaldehyde resin (PFR) retention aid system is affected by the chemical structure and the molecular weight distribution of PFR.1NMR and high performance liquid chromatography have been used to characterise various resole and novolak-based resins. Of the resins examined, those with the highest molecular weight gave the greatest retention improvement. The type of substitution around the aromatic ring of the resin appears to affect the interaction with PEO and the size and structure of the network formed when PFR and PEO are mixed together.

ISSN:0277-3813    

DOI:10.1080/02773819308020518

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0277-3813    

DOI:10.1080/02773819308020511

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor