Untersuchungen zur Vernetzung technischer Sulfitablauge

Nimz, Horst; Gurang, Iradj; Mogharab, Iradj

doi:10.1002/jlac.197619760731

Cited by 14 publications

(6 citation statements)

References 17 publications

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“…Consequently, these reactive sites should amount to 0,3 1 per monomeric phenylpropane unit, a value in general agreement with the previously established (Nimz et al 1976;Van der Klashorst 1982) total value of 0,4 free phenolic hydroxy groups per monomeric unit of spruce lignosulphonate. It nowfollows from the 9,92 carbon atoms per monomeric l 495 unit that ^ n^ =0,151 mol of monomeric phenylpropane units are present, giving rise to a coupling value of 0,151 A remarkably constant coupling value of 0,3 1 was obtained for spruce lignosulphonate.…”

Section: Va Vbsupporting

confidence: 89%

“…Highly coloured water soluble products resulted.. Extensive foaming, indicating decomposition of the reagent, was observed. · The possibility of carbohydrate residues being bound to the lignin (Nimz 1976) was not taken into account in these considerations. Extraction of the acidified reaction mixture with ether removed some of the decomposition products.…”

Section: Va Vbmentioning

confidence: 99%

“…A preliminary investigation of several potentially useful Crosslinking reactions recently conducted (Nimz et al 1976), and an earlier study by Nikitin and Kroshilova (1965), showed that aryldiazonium ions are potentially useful Crosslinking agents for lignin and, in particular, for lignosulphonate. Subsequently, a detailed investigation of the reactions of aryl diazonium ions with lignosulphonate model compounds (Psotta and Forbes 1983) 1 showed Part l of this series that the guaiacyl lignosulphonate model compound la coupled with these ions exclusively, and in high yield, in the position ortho to the phenolic hydroxy group.…”

Section: Introductionmentioning

confidence: 99%

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Lignosulphonate Crosslinking Reactions - 2. The Coupling of Lignosulphonate with Diazonium Salts

Forbes¹,

Psotta²

1983

Holzforschung

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Keywords Lignosulphonate Diazonium salts Diazo coupling Crosslinking reactions Schlüsselwörter (Sachgebiete) Ligninsulfonsäure Diazoniumsalze Diazokupplung Vernetzungsreaktionen Lignosulphonate Crosslinking Reactions. 2. The Coupling of Lignosulphonate with Diazonium Salts SummarySpruce (Picea excelsa) and Wattle (Acacia mearnsii) lignosulphonates were reactcd with benzenediazoniumbisulphate, p-nitrobenzenediazoniumbisulphate and 4,4'-bis(biphenyl)diazoniumbisulphate. The extent to which azo groups were introduced, was calculated from the C:N ratios of the resulting products. Typically 0,3-0,45 azo groups were found for each monomeric lignin unit. Reaction with 4,4'bis(biphenyl)diazoniumbisulphate afforded resinous products, the wattle resin being more highly crosslinked than the spruce resin. Base hydrolysis of the lignosulphonate prior to diazo-coupling was found to affect the spruce resin adversely, whilst it had a positive effect on the wattle resin. Residual sulphite ions in the lignosulphonate were shown to necessitate the use of excess diazonium salt. Vernetzungsreaktionen der Ligninsulfonsäure. 2. Mitt. Die Reaktion der Ligninsulfonsäure mit DiazoniumsalzenZusammenfassung Die Reaktionen von Fichten-(Picea excelsa) und Wattle-(Acacia mearnsii) Ligninsulfonsäuren mit Diazoniumsalzen wurden untersucht. In welchem Umfang Azo-Gruppen eingeführt wurden, konnte aus dem C:N Verhältnis des erhaltenen Produkts berechnet werden. Im Durchschnitt wurden 0,3-0,45 Azo-Gruppen pro Phenylpropan-Einheit eingeführt. Die Reaktion von 4,4'-Bis (biphenyl) diazoniumbisulfat mit Ligninsulfonsäure führte zu harzartigen Produkten, von denen das Wattle-Harz bedeutend besser vernetzt war als das Produkt aus Fichtenholz. Eine noch bessere Vernetzung der Wattleligninsulfonsäure konnte durch eine vorherige alkalische Hydrolyse erzielt werden; die gleiche Behandlung der Fichtenligninsulfonsäure führte zu einem erheblich weniger vernetzten Produkt. Noch in der Ligninsulfonsäure vorhandene Sulfitionen erfordern eine höhere Menge an Diazoniumsalz. S0 3 Na MeO 2Only about 50% of the monomeric phenylpropane units in commercially produced lignosulphonate are sulphonated (Glcnnie 1971).

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Section: Va Vbsupporting

confidence: 89%

Section: Va Vbmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lignosulphonate Crosslinking Reactions - 2. The Coupling of Lignosulphonate with Diazonium Salts

Forbes¹,

Psotta²

1983

Holzforschung

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“…The second involved a mixture of urea, furfural, lignin, petroleum resin, drying oil, wax, and an oxidation catalyst as a crosslinking mixture.Systems conceptually involving only oxidative cross-linking reac tions of lignosulfonates were studied (see Scheme 1). The crosslinking material included spent sulfite liquor, potassium ferricyanide, and H202 in percentages of 25%, 0.5-1.0% and 3.0%, respectively (calculated as water-free reagents, dry wood percent basis), and gave particle board of IB of 102-122 psi at a density of 0.73-0.78 g/cm 3(106), or an IB of 115 psi at a density of 0.56 g/cm 3(107). The water resistance was generally not great unless paraffin emulsion was added.…”

mentioning

confidence: 99%

Activation of Wood Surface and Nonconventional Bonding

Zavarin

1984

Advances in Chemistry

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“…The idea of using a phenol oxidase to enhance the adhesive properties of lignin or wood components has been known for the past two decades (Nimz et al 1976). Due to limited availability of these enzymes, only a small number of investigations have been made in this area.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Auto Adhesion of Wood Fibers Using Phenol Oxidases

Felby¹,

Pedersen²,

Nielsen³

1997

Holzforschung

123

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Enzymatic oxidation of lignin phenolic hydroxyl groups can enhance the level of auto adhesion between wood fibers. Previous investigations within the area have not taken the adhesive effect of proteins and carbohydrates in the enzyme solution into consideration, and part of ι he claimed enzyme generated adhesion may merely be a result of the adhesive effect of the proteins and carbohydrates in the enzyme solution. In this paper the enzyme laccase is used to oxidize beech (Fagux sylvatica) wood fibers. Laccase catalyzes a one-electron oxidation of phenolic hydroxyl groups while reducing oxygen, yielding phcnoxy radicals and water. Wet and dry process fiberboards are made from enzyme treated and untreated beech wood fibers. The enzyme treated fiberboards have significantly higher modulus of rupture and modulus of elasticity as well as better dimensional stability. No effect of the protein and carbohydrate content in the enzyme solution upon the mechanical properties and dimensional stability can be found. The bonding effect is caused by the catalytic effect of the enzyme only. Electron spin resonance spcctroscopy of beech wood fibers shows that a considerable amount of the laccase generated radicals is stabilized in the lignin polymer, and the bonding mechanism appears to be associated with reactions of these free radicals. The physico-mechanical parameters of the enzyme treated fiberboards have not been optimized in the present work. Hence, strength improvements may be obtained simply by optimizing the process parameters. The possibility of producing a medium density fiberboard without the use of synthetic adhesives appears to be promising. The use of oxidative enzymes in processing and manufacturing of wood-based materials may yield new and more environmentally safe products.

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Untersuchungen zur Vernetzung technischer Sulfitablauge

Cited by 14 publications

References 17 publications

Lignosulphonate Crosslinking Reactions - 2. The Coupling of Lignosulphonate with Diazonium Salts

Lignosulphonate Crosslinking Reactions - 2. The Coupling of Lignosulphonate with Diazonium Salts

Activation of Wood Surface and Nonconventional Bonding

Enhanced Auto Adhesion of Wood Fibers Using Phenol Oxidases

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