Method of Papermaking

Abstract

An inventive method of papermaking can be provided for creating an optimum wet end environment. In a preferred method, an aqueous solution of sodium hypochlorite acidified by hydrochloric acid to have a pH of greater than or equal to 4 and less than 7 and adjusted to have an effective chlorine concentration of 1,000 to 10,000 ppm, preferably 3,000 to 8,000 ppm is prepared and charged to a white water pit in a manner to be effective chlorine concentration therein to greater than or equal to 0.5 ppm. Before a step of papermaking, it is preferred that aqueous solution sodium hypochlorite having pH of greater than or equal to 4 and less than 7 is added continuously or intermittently to a raw material water with the expectation that at breaching a residual chlorine concentration becomes greater than or equal to 500 ppm.

1 . A method of papermaking which comprises subjecting a papermaking raw water to a treatment of de-lignin and de-inking and adding some necessary treating agents into a white water wherein in place of one or more of the treating agents an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water with the expectation that at the time of charging a residual chlorine concentration is kept at the concentration of more than 0.5 ppm. 
     
     
         2 . A method of papermaking according to  claim 1 , which further comprises a step of bleaching a papermaking raw water wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water with the expectation that at the time of bleaching a residual chlorine concentration in the papermaking raw water is kept at the concentration of more than 500 ppm. 
     
     
         3 . A method of papermaking according to  claim 1 , which further comprises making the white water circulating wherein in place of one or more of the treating agents an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water with the expectation that at the time of charging a residual chlorine concentration is kept at the concentration of less than 20 ppm, preferably less than 10 ppm. 
     
     
         4 . A method of papermaking according to  claim 1 , which further comprises making the white water circulating wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared and charged into the white water with the expectation that at the time of circulating a residual chlorine concentration in the white water is kept at the concentration of less than 5 ppm, preferably 0.1 to 3 ppm. 
     
     
         5 . A method of papermaking according to  claim 1 , which further comprises making the white water circulating wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared and charged into the white water with the expectation that at the time of circulating a residual chlorine concentration out of the white water circulating is kept at the concentration of less than 1 ppm. 
     
     
         6 . A method of papermaking according to  claim 1 , which further comprises making the white water circulating wherein an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared and charged into the white water with the expectation that according to a value of BOD or COD in a waste water a residual chlorine concentration in the waste water is kept at the concentration of more than 10 ppm. 
     
     
         7 . A method of papermaking according to  claim 6 , wherein the waste water kept at the concentration of more than 10 ppm is re-used for processing water. 
     
     
         8 . A method of papermaking from used paper, wherein number of bacterium in the circulating white water is controlled to be kept less than 10 5 , preferably 10 4 . 
     
     
         9 . A method of papermaking which comprises subjecting a papermaking raw water to a treatment of de-lignin and de-inking, bleaching a white water, papermaking the white water and then discharging a waste water treated by necessary treating agents, wherein in place of one or more of the treating agents an aqueous solution containing ions of hypochloric acid or chlorous acid is prepared to have pH of greater than or equal to 4 and less than 7 and charged continuously or intermittently into the white water in one or more of the all step, change of oxidation-reduction potential before and after charging the aqueous solution in the white water and the waste water is measured and the charging amount of the aqueous solution is automatically controlled according to the measuring signal. 
     
     
         10 . A method of paper making according to  claim 9 , wherein pH value before and after charging the aqueous solution in the white water and the waste water is measured together with the oxidation-reduction potential.