onent b(i) above) was defined as apolymer having a magnesium building capacity of at least 3.0 moles/kg at 25 C and being selected from compounds having the empirical formula I(FORMULA)wherein X is CH2, Y is a comonomer or comonomer mixture, R1 and R2 are bleach and alkali-stable polymer-end groups, R3 is H or C1-4 alkyl, M is H, alkali metal, alkaline earth metal, ammonium or substituted ammoniu