Manufacture of articles such as boards and sheets from fibrous vegetable materials

Claim 1

THE MANUFACTURE OF A WATER-REPELLENT, RIGID PRODUCT OF GREAT DRY AND WET STRENGTH FROM FIBROUS VEGETABLE MATERIAL, WHICH COMPRISES THE STEPS OF MIXING THE FIBROUS VEGETABLE MATERIAL WITH SUBSTANTIALLY TEN TIMES ITS WEIGHT OF A 1.5 PER CENT CAUSTIC SODA SOLUTION AND SUBJECTING THE MIXTURE FOR ABOUT THREE HOURS TO A STEAM PRESSURE OF SUBSTANTIALLY 40 POUNDS PER SQUARE INCH TO FORM A PULP, WASHING THE PULP TO REMOVE AN EXCESS OF CAUSTIC SODA, REDUCING THE WATER CONTENT TO ABOUT 50 PER CENT, MIXING A 5 PER CENT SOLUTION OF CALCIUM HYDROXIDE TO THE PULP IN A QUANTITY OF THE HYDROXIDE EQUIVALENT TO ABOUT 10 PER CENT OF THE DRY FIBROUS MATERIAL, DILUTING THE PULP WITH WATER TO FORM A SLURRY, STIRRING THE SLURRY, ADDING TO THE SLURRY WHILE BEING STIRRED A SOLUTION OF AMMONIUM CARBONATE IN A QUANTITY SUFFICIENT TO PRECIPITATE SUBSTANTIALLY ALL THE CALCIUM OF THE CALCIUM HYDROXIDE AS CALCIUM CARBONATE, SUBSEQUENTLY FORMING THE ARTICLES, THEREAFTER DRYING THE ARTICLES, AND THEN SUBJECTING THE DRIED ARTICLES TO AN ADDITIONAL HEAT TREATMENT AT A TEMPERATURE BETWEEN AN INCLUDING 100* AND 160* C. FOR ABOUT 6 TO 24 HOURS.