Tannine als Bindemittel in Holzwerkstoffen. Teil 1: Eigenschaften tanninhaltiger Fichtenrindenextrakte

Tannin-containing extracts of spruce bark were produced using water, urea solution and sulphite liquor as extraction agents. The extracts of spruce bark were used as partial substitute for quebracho tannin. Particle boards were manufactured with a binder made of quebracho tannin combined with the hot water extract of the spruce bark or a mixture of spruce bark extract/lingin (extract portion: up to 40 %) and formaldehyde as hardener 10,5 % of formaldehyde related to tannin and tannin/extract respectively). The strength of these particle boards corresponds to the requirements of the board type V 100 (bonding resistant to high air humidity). Regarding their strength properties, medium density fibre boards (MDF) bonded with a resin made of quebracho tannin combined with the hot water extract of spruce bark (extract portion up to approx. 60 %) and formaldehyde (10,5 % of formaldehyde related to tannin and tannin/extract respectively) are suitable for the use in humid areas. MDF bonded with a resin made of 100 % extract of spruce bark and formaldehyde (5,3 % of formaldehyde related to tannin and tannin/extract respectively) fulfil the requirements of boards produced for the use in dry areas