A new class of bleaching and brightness stabilizing agents. Part II: Bleaching power of a bisphosphine

Recently we discovered that simple, water-soluble phosphorus compounds such as tris(hydroxymethyl)phosphine, P(CH2OH)(3) (THP), were effective bleaching agents for mechanical pulps over a wide range of consistency, pH and temperature. Now, we have found a bisphoslethine derivative of THP, 1,2-bis[bis(hydroxymethyl)phosphino]ethane, (HOCH2)(2)PCH2CH2P(CH2OH)(2)(BBHPE),to be even more effective than THP. This derivative pable of providing an ISO brightness gain of 13.0 and 15.2 points to spruce and pine thermomechanical pulps (TMP), respectively, compared to a maximum ISO brightness gain of similar to 10.0 points achievable with THP or sodium hydrosulphite. BBHPE is particularly useful as a bleaching agent for pulps that have a poor bleach response to sodium hydrosulphite. It also shows promise as a complementary bleaching agent to alkaline hydrogen peroxide. The bisphosphonium sulphate [(HOCH2)(3)pCH(2)CH(2)P(CH2OH)(3)]SO4 has also been synthesized and shown to be nearly as effective as BBHPE for the bleaching of spruce TMP and peroxide-bleached spruce TMP.