摘要:

Pretreating pine chips (Pinus sylvestris) with sodium hydroxide prior to the alkaline delignification (kraft, kraft-anthraquinone, and soda-anthraquinone) can facilitate the recovery of the carbohydrate degradation products from alkaline pulping liquors. Under suitable pretreatment conditions large amounts of carbohydrate degradation products (aliphatic acids) were formed relative to lignin. The lignin fraction was composed of comparatively low-molecular-weight fragments. Although the delignification was considerably retarded and the yield (based on wood) was decreased by 1–3%, the properties of the resulting pulp were essentially maintained despite pretreatment. Finally, data are given for the composition of aliphatic acids in liquors resulting from pretreatments.

ISSN:0277-3813    

DOI:10.1080/02773818408070658

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Acetoguaiacone and propioguaiacone were found to be the dominant lignin monomeric products (molar ratio 1.3 to 1) from the spent liquor of hemlock pulped with ammonium sulfide/methanol/water. The combined amounts of the ketones were as high as 3.5% based on wood. This is higher than reported monomer quantities from any other pulping process.

ISSN:0277-3813    

DOI:10.1080/02773818408070659

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Eastern black spruce,Picea mariana, chips have been treated to high yields, at temperatures from 120° to 150°C, with sodium bisulphite solutions of pH 4 and total SO2concentrations from 0.23 to 1.92 mol L−1. The rate of sulphonation depends on the concentration of sites available for sulphonation and total SO2 concentration to the power of 0.4; it increases by approximately 70 percent for each 10°C temperature rise. It is postulated that sulphonation at pH 4 occurs by two mechanisms, one which is dependent on total SO2concentration and involves a quinonemethide intermediate and one which is independent of total SO2concentration and involves a carbonium ion intermediate.

ISSN:0277-3813    

DOI:10.1080/02773818408070660

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A variety of hardwoods and softwoods were cooked under identical conditions (constant alkali charge, temperature and time) and yielded pulps of widely varying Kappa number but essentially constant viscosity. Wood species is therefore not a significant factor in determining the viscosity of unbleached pulp. This observation indicates that the G-factor equation for viscosity prediction (so far examined only for spruce) may have a wide applicability.

ISSN:0277-3813    

DOI:10.1080/02773818408070661

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In many commercial processes cellulose is exposed to elevated temperatures in the 100 to 200°C range. Though this range is below the glass transition temperature (Tg) of dry cellulose, in the presence of polar media Tg is depressed, and molecular mobility is sufficient to allow structural reorganization. In the present study, a number of regenerated celluloses, some amorphous and some semicrystalline, were heat treated at elevated temperatures in water under pressure, as well as in other polar media. Two groups of factors were found to influence the type and amount of structural change. The first were the characteristics of the cellulose, that is, the degree of polymerization (DP) and the structure of the cellulose prior to treatment. The other group were the nature of the medium and the time and temperature of the treatment. The amorphous high DP celluloses were found to aggregate as cellulose IV, with the time and temperature determining the extent of ordering rather than resulting in qualitative reorganization. The low DP celluloses, which were of low enough molecular weight to reduce the constraints on molecular mobility imposed by molecular entanglements, had a more diverse pattern of responses. At ambient temperatures the aggregation was into high crystallinity cellulose II; at intermediate temperatures, a variety of forms fitting into the category of cellulose IV were produced; and finally, at high enough temperatures, a cellulose I of very high crystallinity was produced in low yield.

ISSN:0277-3813    

DOI:10.1080/02773818408070662

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

When wood was treated with 23% aqueous sodium hydroxide followed by washing with water and drying, no lattice conversion of cellulose was observed under the experimental conditions employed. On the other hand, wood subjected to a pretreatment that results in the loosening of its morphological texture, upon mercerization, showed a varying degree of lattice conversion. The explosion process and the TFA (trifluoroacetic acid) treatment were used to achieve the loosening of wood texture. The lattice conversion of cellulose was studied by X-ray diffractograms. The extent of lattice conversion was found to depend on the conditions of the pretreatment used to achieve the loosening of wood texture. The extent of lattice conversion increased with an increase in the explosion temperature and the time at temperature, within the range of these experiments. Increased duration of TFA pretreatment, at a particular temperature, resulted in a higher degree of lattice conversion. These observed facts have been ascribed to the extent of loosening of the morphological texture of wood, which allows comparatively free swelling of cellulose in alkali.

ISSN:0277-3813    

DOI:10.1080/02773818408070663

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Colorimetry gave consistently lower uronic anhydride values for four species of wood than did measurement by evolved CO2. These differences were partly related to CO2evolution from nonuronide wood extractives, and partly to CO2from nonuronide carbohydrates or lignin. After the usual benzene-ethanol extraction to remove interfering extractives, the uronic anhydride contents by gravimetric CO2analyses were still 30 to 40% higher than those by colorimetry. Based upon the greater selectivity of the colorimetric method, the authors conclude that colorimetry provides the more accurate uronic anhydride analyses of natural materials.

ISSN:0277-3813    

DOI:10.1080/02773818408070664

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The chemical characterization (functional group distribution) and spectroscopic properties (13C,1H, IR, UV-Vis) of a number of lignins obtained from ethanol extraction of explosively-decompressed aspen (Populus tremuloides) lignin (EEEDAL) are described. In this process mod is heated to ∼240°C by direct steam and fiberized by sudden decompression. Both mechanical and chemical degradation occur which lead to a decrease of the molecular weight of all of the natural polymers. The lignin fraction is soluble in alcohols; it has a low number average molecular weight (925) and is very reactive. EEEDAL was subjected to fractionation by differential solubility prior to and after electrolyses on mercury cathodes at −2.6 V vs. Ag/AgCl in methanol/tetraethyl-ammonium perchlorate. After recovery of 85–90% of the original weight of material used by precipitation with acid, followed by a series of extractions, the chemical and spectroscopic properties of each fraction were determined. The acid-insoluble fractions are more condensed than the acid-soluble fractions and have lower phenolic OH and lower aliphatic OH contents than the acid-soluble fractions. The acid-soluble fractions phenolic OH content approaches one per phenylpropane (5) unit of the Lignin. Electrolyses increase the amount of lower molecular weight, high phenolic content, acid-soluble lignins and changes the molecular weight distribution by decreasing the polydispersity of the resulting lignins. These low-molecular-weight lignins are chemically reactive (for instance, with formaldehyde) and can be used in the partial replacement of phenol in phenol-formaldehyde thermosetting resins.

ISSN:0277-3813    

DOI:10.1080/02773818408070665

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Various solvent systems capable of dissolving cellulose have been reported in the literature. Cuene (cupriethylene diamine hydroxide) and FeTNa (ferric sodium tartrate) are well known examples. Preliminary experiments were conducted with Cuene and FeTNa to determine if the cellulose dissolving ability of these systems could be used to bond yellow birch veneers. The results indicate that relatively high dry shear strengths, and low wet shear strengths are obtained.

ISSN:0277-3813    

DOI:10.1080/02773818408070666

出版商:Taylor & Francis Group    

年代:1984

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:10.1080/02773818408070657

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor