Fate and influence of western red cedar extractives in mechanical pulping

The methanol extractives from western red cedar mechanical pulps were found to be radically different in composition to the extractives obtained from the heartwood. The major heartwood extractive components, the tropolones an d lignans, were not present in the extractives from the pulps. However, the proportion of a brown polymer doubled. The low and high molecular weight m ethanol extractives components from the pulps were separated using methyl t ert-butyl ether. The low molecular fraction contained mostly guaiacyl-based compounds with dihydroquercetin, thujic acid, 3-hydroxy-1-(4'-hydroxy-3'-m ethoxyphenyl) -2-oxopropane and 4-ethyl-2-methoxy-6-hydroxyphenol being pos itively identified. The brown polymeric portion had molecular weights rangi ng from 1,000 to 10,000. Infrared analysis indicated that the polymers were formed from lignans. Examination of the changes in diffuse reflectance UV- visible and infra red spectra of the pulps on extraction with methanol, sug gested that the colour resides in insoluble polymers formed from plicatic a cid/plicatin during refining.