Pulp refining

Claim 1

IN THE COLD-CAUSTIC REFINING OF WOOD PULP AT A TEMPERATURE OF FROM 5* TO 40*C. TO PRODUCE HIGH-ALPHA CELLULOSE THE IMPROVEMENT WHICH COMRPISES SLURRYING A CELLULOSE PULP WITH ABOUT A 1 TO 3% CAUSTIC SOLUTION AT A CONSISTENCY OF FROM 1.5 TO 5%, COMPRESSING THE SLURRY TO REMOVE THE SOLUTION TO A CONSISTENCY OF FROM 10 TO 35%, INCREASING THE CAUSTIC CONCENTRATION ON THE PULP TO ABOUT 10% IN A SUCCESSION OF SOLUTION ADDITIONS AND EXTRACTIONS IN WHICH A WEAKER CAUSTIC SOLUTION IS DISPLACED WITH A FED BACK STRONGER CAUSTIC SOLUTION AND THE CONSISTENCY IS INCREASED TO FROM 10 TO 35%, REMOVING A PART OF THE SOLUTION CONTAINING UP TO ABOUT 10% OF CAUSTIC WHICH CONTAINS HEMICELLULOSE AND OTHER IMPURITIES FROM THE PROCESS, ADDING 10% CAUSTIC SOLUTION TO RESLURRY, SUBJECTING THE PULP TO AGITATION FOR FROM 5 TO 30 MINUTES AT A LOWER CONSISTENCY WITH A CAUSTIC SOLUTION OF ABOUT 10%, THEN EFFECTING A REMOVAL OF THE CAUSTIC SOLTUION FROM THE PULP BY SUCCESSIVELY DISPLACING THE STRONGER CAUSTIC SOLTUION WITH A WEAKER CAUSTIC SOLUTION, AND WASHING THE PULP WITH WATER.