D
SECTION D — TEXTILES; PAPER
  
PAPER
 D21
PAPER-MAKING; PRODUCTION OF CELLULOSE
 D21D
TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE  [5]
P:0 D21D 1/00
Methods of beating or refining; Beaters of the Hollander type (knotter screens D21F)
P:10 D21D 5/00
Purification of the pulp suspension by mechanical means; Apparatus therefor (centrifuges, cyclones B04)
P:20 D21D 99/00
Subject matter not provided for in other groups of this subclass  [8]