Mimosa tannin

Contradictory opinions have been referred to in the literature particularly on the nature of the iron-tarmate and its interaction with the rusted steel due to the diversity of the material used in different studies. Studies have included the use of tannic acid [7-10], gallic acid [11], oak tannin [12, 13], pine tannin [14] and mimosa tannin [15]. In order to establish the correlation between the ferric-taimate formation and the low inhibition efficiency observed at high pH from the electrochemical studies, phase transformations of pre-rusted steels in the presence of tannins were evaluated. In this work the quantum chemical calculations are conducted to analyse the relationship between the molecular stracture and properties of ferric-taimate complex and its inhibitory mechanism. 

The only tannins in the world currently being commercially exploited for adhesive applications are those isolated by hot- (or cold-) water extraction of Acacia meamsii bark in the province of Natal, South Africa. Approximately 100,000 tons of mimosa tannin were being produced annually as reported in 1980, the latest year for which production figures were available (41)- Of this amount, about 10,000 tons were used in adhesive applications mainly in South Africa, Australia, and New Zealand. While this number is not large in light of the 300,000 to 400,000 tons of phenol used annually in resins, it does provide evidence that bark tannins can be economically used for adhesives. This application is facilitated by the relatively high cost of phenol and resorcinol in... 

Early attempts to use mimosa tannin in particleboard adhesives involved high-temperature alkaline treatment of the extract to reduce viscosity of the 40% solids level needed (43,44) Subsequent improvements followed the same course as with plywood, namely the use of phenol-formaldehyde or phenol-resorcinol-formaldehyde as crosslinking agents (45) and the use of catalysts or mix modifications to reduce press temperature requirements and to extend pot life. Recent work (46) has shown that exterior chipboard adhesives can also be prepared by crosslinking of mimosa tannins with 4,4-diphenylmethane diisocyanate. 

Tannin-based adhesives have been studied by many researchers for the past 30 years [3, 7-14]. Nowadays, tannins are commercially produced e.g., mimosa tannins in Brazil, South Africa, India, Zimbabwe and Tanzania. On the other hand, quabracho tannin is produced in Argentina, mangrove tannin in Indonesia, whilst both Italy and Slovenia produce chestnut tannin [15]. 

Comparative gel times (s) of Acacia mangium tannin, commercial mimosa tannin and quebracho tannin at different pH levels... 

Mimosa tannin extract (supplied by Silva, S. Michele Mondovi , Italy) of Stiasny value of 92.2 [17-19] was used. The tannin solution in water was prepared at 45% concentration and its pH adjusted to 10.4 with a 33% NaOH aqueous solution. The high pH was chosen as the hardener used performs best at such a pH [3]. The hardener used was 5% hexamethylenetetramine (hexamine) on tannin solids. This was added to the tannin extract solution as a 30% aqueous solution. 

As regards the tannin origin by location, the areas of strong industrial production today are Brazil, South A ica, India, Zimbabwe, Tanzania for mimosa tannin Argentina for quebracho tannin Indonesia for mangrove and for cube Gambier tannins and Italy and Slovenia for chestnut tannin. Tha-e are many other small to very small producers a bit everywhere, for example, small pine tannin factories in Turkey and Chile, an oak tannin factory in Poland and a grape pip tannin factory in France. 

Vanillic acid, catechol, mimosa tannin and tannic acid onto TMP Paper with improved tensile strength and water resistance [101-103]... 

Toth G 1982 Penetration rate of mimosa tannin in pelt. Contributions to dry tanning. Ds Leder 33(2) 17-28... 

One way to assure low raw material costs is to have multiple use of the material. If wood chips, sawdust, or bark is to be extracted, the residue should be useful for another purpose. Examples of this approach are 1) Isolation of arabinogalac-tan gum from western larch Larix occidentalis) heartwood chips followed by kraft pulping of the extracted chips 2) isolation of mimosa tannins from bark of trees in which the peeled wood Acacia sp.) serves as raw material for chemical cellulose production (South Africa) and 3) tall oil separation from the concentrated black liquor derived from kraft pulping of southern pines. In each of these cases the brunt of the raw material cost is carried by some product other than the extractive. Assurance of low raw material costs virtually dictates extractive isolation and processing ancillary to a forest products processing plant. 

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