Wattle tannins

The vinyl grafted wattle tannin [872] comprises a wattle tannin grafted with AMPS and small amounts of acrylamide. The wattle tannin is present in an amount between 2% and 14% by weight. The AMPS is present in an amount between 98% and 84% accordingly. 

Wattle tannin, vinyl grafted AMPS and acrylamide [872]... 

D. A. Huddleston, R. K. Gabel, and C. D. Williamson. Method for reducing fluid loss from oilfield cement slurries using vinyl grafted wattle tannin. Patent US 5134215,1992. 

Condensed tannins were considered to be highly recalcitrant to biodegradation until Basaraba (3) reported that some bacterial isolates could utilize wattle tannin as both a carbon and energy source. Later, Lewis and Starkey... 

Bacillus, Klebsiella, Cornybacterium, and Pseudomonas being the most frequently observed. The capacity of these bacteria to degrade tannins, and detoxify bark chips or barks extracts, was further demonstrated with pine (Pinus maritima) (51), oak (Quercus pedonculata) and gaboon wood (Aucoumea kleneana) barks (52). The degradation of quebracho and wattle tannins was also confirmed in pure cultures (53). 

Interest in use of condensed tannins as components of adhesive formulations began about three decades ago. While research studies have been carried out in widely scattered laboratories around the world, three major areas of activity can be distinguished. These are 1) development of bark extracts and commercial production facilities on the west coast of North America, 1953 to 1975 2) application of tannins in adhesive formulations in South Africa based on indigenously produced mimosa (wattle) tannin, early 1970 s to the present and 3) a resurgence of interest in pine bark as raw material for tannin-based adhesives, beginning in the middle 1970 s. Each of these activities has been characterized by parallel efforts on structural identification of the tannins and development of unique methods for incorporating the isolated tannins into adhesives. 

The resorcinol-pattern proanthocyanidins are widely used not only for leather tanning, but also for a range of other commercial products, particularly as adhesives for plywood and fiberboard (6,7). Wattle tannin is produced from sustained-yield forests of Acacia mearnsii. largely in southern Africa (6,8). Some of the impetus at least to develop other uses for wattle tannin, apart from... 

Problems and facts that in the author s personal experience arise in the industrial application of tannin-based adhesives for timber sometimes indicate lack of correspondence with laboratory practice and results. These are often problems related to unusual characteristics of the adhesive itself, or of its application technique, which could not be noticed during research under laboratory conditions, but the existence of which could easily jeopardize successful implementation of laboratory technology into industrial practice. Correcting the credibility gap between research focus and industrial usage is seen as a critical step toward market expansion for these new products. Important considerations are consistency of tannins, extracts and adhesives properties due to the natural raw material variability formulation in cold-setting adhesives and application conditions (such as wood moisture and adhesive-content or pressing time) in particleboard adhesives. These problems have been overcome in use of wattle tannin-based adhesives as shown by a visual comparison of tannin-, phenolic-, and melamine-bonded particleboards exposed to the weather for 15 years and the growing use of tannin-based adhesives in other countries. 

Wattle tannin resins are also used to manufacture other resins, such as foams comparable to phenolics, as waterproofing additives, and binders for corrugated cardboard or charcoal briquettes. This discussion, however, deals only with particleboard, plywood, glulam, and finger-jointing exterior-grade wood adhesives. Formulations of the adhesives will be mentioned ad hoc, if at all necessary, as they have already been extensively discussed in articles and reviews in the relevant literature.(7)... 

Table II. Comparison of Approximate Industrial Conditions of Application for Particleboard Bonded with Wattle Tannin Adhesives...

Figure 4. Photographic comparison of 12 mm thick exterior grade commercial particleboards manufactured in the same industrial plant and bonded with MUF, wattle tannin-formadehyde, and PF resins The panels were exposed at the CSIR testing site (4,500 feet above sea level) at Pretoria, South Africa for 15 years. Note the extensive degeneration of MUF board (commerically imported MUF resins from West Germany). Also note the more marked edge and surface degeneration of the PF in comparison to the TF-bonded boards.

Figure 5. World production and use of wattle tannin-based adhesives.

Tannins. Herb Hergert s introduction (Chapter 12) to the use of condensed tannins in adhesives is especially interesting because he provides some reasons why commercial success is lacking in the use of condensed tannins from conifer barks despite substantial effort worldwide to parallel the South African success in the use of wattle tannins. Much of the problem in the use of conifer bark tannins remains centered on our inadequate understanding of the fundamental chemistry of these polymers. For example, Lawrence Porter (Chapter 13) provided the first measurements of the viscosities of solutions of purified condensed tannin isolates of known molecular weight and the reactions of these polymers with formaldehyde. It is incredible that this has not been done previously considering the hundreds of papers that have been published on tannin use in wood adhesives. Further evidence for the comparatively limited knowledge... 

Progress in the use of condensed tannins in adhesive formulations might be expected to be more rapid than is the case for lignins because of the impetus provided by the commercialization of wattle tannin-based adhesives and because of the extraordinarily high reactivity of tannins in reactions with formaldehyde. This reactivity offers an opportunity to substitute tannin for resorcinol (currently priced at about 1.80/lb) instead of phenol (about 0.40/lb). Now that wattle tannins have been successfully introduced, their application can be expected to continue to expand. The situation remains difficult, on the other hand, for use of conifer bark tannins in adhesives. Herb Hergert is certainly... 

Tannins have been shown to retard markedly the decomposition of organic substances. Basaraba and Starkey (1966) observed that chestnut and wattle tannins formed complexes with gelatin and gliadin and thereby reduced the rate of decomposition of the proteins. The effect of tannin on the decomposition of peptone and an amino acid was much less. Similar studies by Benoit and Starkey (1968) with wattle tannin and various enzymes also showed marked inhibition. Urease was almost completely inactivated when the tannin—urease ratio was 1/10, whereas for a similar degree of inactivation a ratio of... 

Natural phenolic compounds are used as both replacements for substantial portions of synthetic phenol in plywood adhesive resins and as glue mix additives to improve performance 4 to 6% is added, based on phenolic resin solids. They bring about improvements in assembly time tolerance and flow with no significant change in adhesion. Glue mix additions of wattle tannin or other condensed flavonoid tannin extracts with or... 

The adhesive developed for the manufacture of damp-ply-resistant corrugated cardboard are based on the addition of spray-dried wattle extract, urea-formaldehyde resin, and formaldehyde to a typical Stein-Hall starch formula of 18 to 22% starch content [60,61]. The wattle tannin-urea-formaldehyde copolymer formed in situ, and any free... 

Gallotannin Chestnut tannin Catechin Wattle tannin... 

Effect of wattle tannin on the mycelial growth of A. niger... 

Wattle tannin samples Wattle tannin + glucose (166.7mM) samples... 

Otuk and Deschamps [26], for the first time, reported the capacity of yeasts to degrade a condensed tannin. The biodegradation of wattle tannin with six strains of yeasts, isolated from decaying bark samples, was tested. 

Figure 2. Oxidation of (a) myrobalan tannin and glucose and (b) wattle tannin and glucose by Pseudomonas solanacearum.

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