A solution with a salt-sensitive polymer binder for use in fibrous webs, where the binder contains a copolymer comprising repeat units derived from butyl acrylate, methyl methacrylate and amino functionalized alkyl acrylate or methacrylate or amino functionalized alkyl acrylamide or methacrylamide optionally including monomers such as vinyl acetate and/or vinyl acetate/ethylene. The binder solution is prepared by emulsion-polymerizing a copolymer and then neutralizing the copolymer with acid to make it water soluble. The binders are particularly suitable for strengthening nonwoven fibrous webs in disposable articles such as wet-wipes, personal care products, diapers, and the like and retain their salt-sensitivity with or without divalent metal scavengers.