Patent ID: 8303772

Claim:
A method for preparing an unbleached paper product prepared from cereal straw pulp as a raw material, wherein the method comprises: preparing the cereal straw material before cooking, including: cutting and rubbing the cereal straw material to obtain a cut and rubbed material; dedusting the cut and rubbed material; and screening the dedusted material; (1) cooking the cereal straw material, pressing, washing, disintegration and then performing oxygen delignification treatment to obtain an unbleached straw pulp; wherein the oxygen delignification includes: pumping pulp with a potassium permanganate number of 16-28 obtained after cooking to an oxygen delignification reaction tower and adding sodium hydroxide and oxygen; and allowing delignification reaction of the pulp in an oxygen delignification reaction tower to obtain pulp with a hardness having a potassium permanganate number of 10-14; the oxygen delignification being single stage and executed in the oxygen delignification reaction tower, the pulp being at 95-100° C. and a pressure of 0.9-1.2 MPa at an inlet of the reaction tower and at 100-105° C. and a pressure of 0.2-0.6 MPa at an outlet, alkali used in the oxygen deliqnification treatment being 2-4% of bone dry pulp based on sodium hydroxide, and oxygen added being 20-40 kg for every ton of bone dry pulp, and the pulp reacting in the reaction tower for 60-90 min; (2) beating the unbleached straw pulp and an unbleached wood pulp respectively to obtain beaten pulps; (3) mixing the beaten unbleached straw pulp and the beaten unbleached wood pulp in step (2) based on parts by weight as required by the paper product, and blending the pulp even; and (4) manufacturing with the beaten pulps to obtain the unbleached paper product, wherein the cooking is an ammonium sulfite cooking method in a vertical cooker including: adding cooking liquor to the cereal straw material, in which ammonium sulfite used is 9-15% of a bone dry raw material, and a liquor ratio is 1:6-10; and filling the cereal straw material in hot black liquor in the cooker by a filler, closing a cooker cover after the cooker is full, supplementing the cooking liquor at 130-145° C. while discharging air from the cooker and boosting a pressure to 0.6-0.75 MPa, and heating the cooking liquor to 156-173° C. in which a time for heating, insulating and exchanging is 220 min; and pumping the pulp to a blow tank.