For most tissue makers wet strength resin (WSR) accounts for the major portion of their chemical spending. The economics of wet-strengthened grades largely depend on resin efficiency. The cost pressure also comes from stricter regulations of chloro-organic materials, which are suspected carcinogens.
The three commonly regulated materials found in WSRs are 3-chloro-1.3-propandiol (CPD), 1.3-dichloro-2-propanol (DCP), and absorbable organic chlorine (AOX). The regulators’ concerns arise from the migration of these materials from paper to food or their discharge with waste water, potentially harming people and the environment.
Improving WSR chemistry
Since the mid-1980s, the WSR chemistry has undergone a huge transformation to much lower residual levels of chloro-organics. The existing resins in the market have different levels of CPD, DCP and AOX and are classified as generation (G) 1, 2, 2.5, 3 and 4. The higher the G-number, the cleaner the resin. In the EU countries, the G1 resins are not used anymore since they have to be labeled as toxic and carcinogenic. In addition, G1 resins contain high amounts of unreacted epichlorohydrine. The predominant resins marketed in the EU for tissue are G2 and G2.5; whereas, the cleanest G3 and G4 resins are suitable for coffee filters and tea bags. The cleaner resins are highly technical materials and tend to cost more. Therefore, the main drivers for selecting an optimal WSR are regulatory targets and the cost that has to be balanced out.