Wattle LEATHER

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... 

Use Source of wattle bark extract, used in vegetable tanning of leather, especially retannage of upper leathers and production of heavy leathers. 

D. G. Roux, Wattle Bark and Mimosa Extract. Leather Industries Research Institute, Graham-stown. South Africa (1976). 

Condensed tannins constitute more than 90 per cent of the total world production of commercial tannins (200000 tons per year) [11]. Their high reactivity towards aldehydes and other reagents renders them both chemically and economically more interesting for the preparation of adhesives, resins and other applications apart from leather tanning. The main commercial species, such as mimosa and quebracho, also yield excellent heavy duty leather. Condensed tannins and their flavonoid precursors are known for their wide distribution in nature and particularly for their substantial concentration in the wood and bark of various trees. These include various Acacia (wattle or mimosa bark extract), Schinopsis (quebracho wood extract), Tsuga (hemlock bark extract), Rhus (sumach extract) species, and various Pinus bark extract species, from which commercial tannin extracts are manufactured. 

The leather-tanning industry of India used about 120000 tons of assorted vegetable tannins in 1970 (203). India imported about 25000 tons of wattle extracts to supplement domestically available tannins such as myrobalan nut tannins (3500 tons/year) and wattle tannins (2000 tons per year). Vegetable tannins (primarily mixtures of chestnut, wattle, and quebracho tannins) are also used widely in Italy (173). In the Peoples Republic of China, much of the leather manufactured is made using vegetable tannins. Research efforts are being accelerated on the use of tannins from indigenous plants such as Larix and Firms spp. (Sun and Foo, personal communication 1986). 

Retannage with condensed tannins (wattle or quebracho) was much better than with the hydrolyzable tannins (myrobalans) or chestnut tannins. Wattle tannins reacted more slowly than quebracho tannins. Use of a wattle retannage with neutralization gave the most stable leathers. The wattle tannin were also superior because of the lower level of non-tans as they also reacted with the chromium and increased the amounts of chromium stripped off in the vegetable retannage (13). 

Eye J D, Ficker F C 1982 A pilot plant study of the effects of quebracho and wattle on anaerobic digestion. J Am Leather Chem Assoc 77 137-148... 

Russell A E, Shuttleworth S G, Williams-Wynn D A 1967 Further studies on the mechanism of vegetable tannage. Part III. Solvent reversibility of wattle tannage. J Soc Leather Trades Chem 51(10) 349-361... 

Saayman H M 1967 Manufacture of experimental particleboards using black wattle tannin adhesives. Leather Ind Res Inst Bull 446 1-8... 

Sykes R L, Roux D G 1957 Study of the affinity of black wattle extract constituents. Part IV. Relative affinity of polyphenols for swollen chemically modified collagen. J Soc Leather Trades Chem 41 14-23... 

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