THEIR USE IN WOOD-LAMINAnNG ADHFSIVES: AN EXPLORATORY STUDY

The reaction of a tannin extract (containing about 30"/0 carbohydrate) from loblolly pine (Pinus taeda L.) bark (two parts) and resorcinol (one part) at 12O"C for 24 h with acetic acid catalyst gave a product containing predominantly oligomeric procyanidin-4-resorcinol adducts (3Wo), unreacted resorcinol (22%). carbohydrate (20010). the resorcinol adduct 2R,3R,4S 4-(2.4-dihydroxyphenyl).fIavan-3,3',4',5.7-pentaol (80;0), its 2,3-trans isomer (40;0). and catechin and epicatechin (7%). The above mixture was used as a resorcinol replacement in a conventional phenolresorcinol-formaldehyde laminating adhesive as used in the manufacture of laminated wood beams. Preliminary gluing results suggest that. with some modification of adhesive formulation and resin synthesis conditions. room-temperature curing adhesives for wood-laminating purposes could be produced successfully using such condensed tannin-resorcinol adducts to replace more than (JJ'fo of the resorcinol requirement.