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world pulppaper 43 Inthemanufacture ofaPae resinepireacts withthesecondary aminegroupsof theprepolymerto form aminochlorohydrin G2 G2.5 and G3 resins Polymer Bound Organochlorine PBOX is by far the primary contributor to AOX not the free species 13-DCP and free 3-MCPD. In the manufacture of a PAE resin epi reacts with the secondary amine groups of the prepolymer to form aminochlorohydrin ACH. This ACH species then converts to AZE functionality Figure 2. Additionally epi also reacts with the acidic end groups of the prepolymer to generate Polymer Bound CPD PB-CPD. Both ACH and PB-CPD are examples of Polymer Bound Organochlorine PBOX species. In the AOX methodology the polymeric component of the PAE resin is retained on the activated charcoal and contributes significantly to the measured AOX. Theoretically the AOX content is the sum of the chloride content from the 13-DCP 3-MCPD PB-CPD and polymeric ACH in the PAE resin. The chloride content of 13-DCP is 55 wt and the chloride content of 3-MCPD is 32 wt . The contribution of 3-MCPD to the AOX content of a resin is lower than theoretical because 3-MCPD is not completely adsorbed and retained by activated charcoal in the AOX methodology. Whereas 90-95 of 13-DCP can be retained by activated charcoal typically only 25 of 3-MCPD is retained under the same conditions. This is due to the greater hydrophilic nature of the 3-MCPD molecule. The polymeric component of the PAE resin is considered to be well retained by the activated charcoal in the AOX methodology so an abridged version of the equation AOX PBOX 0.55xDCP has been found to provide a good description of the AOX content of the PAE. Prior to 1990 Generation 1 PAE resins had high levels of AOX mainly due to the high levels of 13-DCP present. The development of Generation 2 wet strength resins resulted not only Figure 5. AOX content relative to the 13-DCP and 3-MCPD Content 12.5 active basis Demonstrating the Contribution from PBOX species polymeric ACH and PB-CPD. in a reduction of 13-DCP by about one order of magnitude but also resulted in a reduction in the AOX content of the PAE resin. An analysis of the relative contributions of the free species 13-DCP and 3-MCPD compared to the PBOX in a G2 PAE resin shows a much higher contribution of PBOX species to the AOX value. This is further exemplified by the application of a post-reaction cleaning technique to a G2 resin to remove only the 13-DCP and 3-MCPD Figure 5. To emphasize the points that 1 AOX and 13-DCP and 3-MCPD are not necessarily directly correlated and 2 that PBOX is a primary contributor to AOX it was discovered that a G1 resin can be designed to have an AOX level that is higher or lower than the 13-DCP level. While the PBOX content decreases from G1 to G2 to G2.5 to G3 the high PBOX content of G2 resins relative to 13-DCP and 3-MCPD content clearly shows that PBOX species are the major contributors to AOX in G2 G2.5 and G3 resins. In practise most of the polymeric component of the PAE resin is retained in the paper product. This retained PBOX does not contribute to the AOX in a mills effluent discharge. A high level of retained PAE resin and therefore a lower AOX in effluent contribution can be achieved by using best practice application techniques e.g. optimum dosing points and use of anionic co-factors. High efficiency PAE resins with a