Improvements in and relating to paper-board manufacture

780,691. Corrugated paper-board. LAWRENCE PAPER CO. Dec. 6, 1955, No. 35029/55. Class 96. Asphalt, e.g. of melting-point 185‹ to 230‹ F. from a hopper 22, Fig. 2, is fed by a screwconveyer 26 past a cold water spray 38, to a hammer-mill grinder 34 delivering through a 30-mesh screen 54 to a similar grinder 36 with a like screen 66, and into the tub of a beater 12, a stack pipe 70 of which has water-showers 72. The beater 12 supplies a chest 76, Fig. la, with pulp for the two middle vats 78, 80 of a four cylinder-mould board-making unit, the outer two being supplied with e.g. asphalt-free pulp prepared from waste paper. The combined web thus formed is couched on to a felt 90, wet pressed, dried at a temperature high enough to melt the asphalt, calendered, watersprayed and reeled. Paper-board unwound from the reel is subjected to steam jets, passed between corrugating rolls, and a liner is adhered to each side thereof.