摘要:

The viscosities of unbleached kraft, kraft-AQ, soda, and soda-AQ pulps were determined over a wide range of additive concentrations and sulphidities, but at constant effective alkali and H-factor. There was no significant effect of AQ or sulphide ion on viscosity. As expected, effective alkali had a large effect on viscosity, while H-factor had a lesser influence. Viscosity is not a reliable indicator of the strengths of unbleached pulps made by reductive alkaline processes.

ISSN:0277-3813    

DOI:10.1080/02773818108085090

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The rates of hydrolysis of the β-aryl ether bond were determined in the temperature range 130° to 155°C for guaiacylglycerol-P (2-methoxyphenyl) ether and its veratryl analogue using both HC1 and AICI3as catalysts in a mixed ethanol-water medium. The data, based on quantitative determinations of guaiacol liberated in the process, demonstrate the absence of competing intramolecular condensation processes. The rates of HCl-catalyzed hydrolyses are first-order with respect to both catalyst and substrate concentrations, higher in dioxane-water than in aqueous or ethanol-water media, and the activation energies were nearly identical for both model compounds, 36.1 and 35.5 kcal/mol, respectively. In general, the hydrolysis of the guaiacyl model was four times faster than that of the veratryl analogue. The catalytic effect of AICI3 appears to be based on HCI released at higher temperatures by gradual hydrolysis.

ISSN:0277-3813    

DOI:10.1080/02773818108085091

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Differential sedimentation of finely ground wood has been used to isolate fractions of black spruce in which the lignin content varied from 20 to 60 percent. The fractions of low lignin content consisted mainly of secondary wall tissue while those of high lignin content came predominantly from the compound middle lamella.

ISSN:0277-3813    

DOI:10.1080/02773818108085092

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Anthraquinone-1-acetic acid is a less effective delignification catalyst than anthraquinone but it gives an enhanced carbohydrate stabilization by converting reducing sugar end groups more effectively to aldonic acid end groups. This reaction produces the hydroquinone form of the additive which is then easily oxidized by oxygen at 80°C. Oxygen treatment favors the end group stabilization. Depolymerization of the cellulose is suppressed by the presence of magnesium hydroxide but cannot be avoided completely.

ISSN:0277-3813    

DOI:10.1080/02773818108085093

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The quinone methide from guaiacylglycol-β-guaiacyl ether [l-(3-methoxy-4-hydroxyphenyl)-2-(2-methoxyphenoxy)ethanol] formed carbon-carbon bonded adducts with both anthrone and anthrahydroquinone (AHQ). It was found that the anthrone adduct [l-(3-methoxy-4-hydroxyphenyl)-1-(anthracen-9-one-10-yl)-2-(2-methoxyphenoxy)ethane] was much more resistant to alkaline degradation than the corresponding AHQ-adduct Jl-(3-methoxy-4-hydroxyphenyl)-l-(10-hydroxyanthracen-9-one-10-yl)-2-(2-methoxyphenoxy)ethane]. It was demonstrated, by NMR spectroscopy that analogous anthrone and AHQ adducts formed with milled wood lignin and had relative alkaline stabilities consistent with those observed with the model adducts. At 10° C the AHQ-lignin adduct partially decomposed to the Y-monoacetates of coniferyl alcohol and p_-coumaryl alcohol which subsequently reacted with excess AHQ to give the novel adducts, trans-1-(3-methoxy-4-hydroxyphenyl)-3-(10-hydroxyanthracen-9-one-10-yl)propene, and trans-1-(4-hydroxyphenyl)-3-(10-hydroxyanthracen-9-one-10-yl) propene, respectively.

ISSN:0277-3813    

DOI:10.1080/02773818108085094

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Zinc oxide as well as lead (II), lead (IV) and tin (II) oxide have been found to react with guaiacol as a simple lignin model compound to form complexes. In comparison with results obtained with chromium trioxide, only zinc oxide is able to give worthwhile results when used to waterproof wood. Because of the “dimeric” character of the complex formed with lignin, zinc oxide is a less efficient wood waterproofer than CrO3, which instead forms “polymeric” complexes. A theory of the preservation effect of wood by metallic ion is advanced. The results obtained indicate that metallic compounds which are capable of further cross-linking the lignin network by forming insoluble complexes with it can act as wood waterproofers. Metallic compounds giving insoluble monomeric complexes not enhancing lignin cross-linking or not giving insoluble complexes do not act as wood waterproofer.

ISSN:0277-3813    

DOI:10.1080/02773818108085095

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The present investigation was undertaken to see if a practical method could be developed for homogeneous tritylation of cellulose in a non-aqueous solvent of cellulose. Our new procedure of tritylation of cellulose can easily be carried out under homogeneous conditions by dissolving cellulose in a sulfur dioxide(SO2)-diethylamine (DEA)-dimethyl sulfoxide(DMSO) solvent system, one or the non-aqueous cellulose solvents, followed by addition of trityl chloride and pyridine. This new method can avoid the time consuming pretreatment for the decrystallization of cellulose which has been necessary in the traditional procedure and can lower the reaction temperature. IR spectra of the products indicated the formation of trityl cellulose. Measurements of dielectric properties of the products confirmed that trityl groups were selectively introduced at the primary hydroxyl groups in cellulose. This conclusion was also confirmed by a H-NMR study in which the tritylated products was first acetylated, detritylated and then trideuterioacetylated and H-NMR spectra were taken at each stage and examined comparatively.

ISSN:0277-3813    

DOI:10.1080/02773818108085096

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0277-3813    

DOI:10.1080/02773818108085089

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor