Polyether bis-phosphonic acid compounds

A method of preparing a polyether bis-phosphonic acid compound comprising the steps of:

• (a) reacting (i) a hydroxyalkylphosphonic acid dialkyl ester compound of the formula ##STR12## where R is selected from the group consisting of --CH.sub.2 -- and --CH.sub.2 CH.sub.2 --, R" is an alkyl group having from 1 to 6 carbons, and M is an alkali metal or an alkaline earth metal, with (ii) a compound selected from the group consisting of 2-benzyloxyalkyl p-toluenesulfonate, 2-benzyloxyalkyl benzenesulfonate and 2-benzyloxyalkyl alkylsulfonate to form a first intermediate, the alkyl group of said alkylsulfonate having from about 1 to 6 carbon atoms, the oxyalkyl group of said sulfonate corresponding to the formula OR' where R' is selected from the group consisting of --CH.sub.2 CH.sub.2 --, and --CH.sub.2 CH.sub.2 -- which is substituted with one or more methyl groups, and the benzene ring of the benzyl group of said sulfonate being optionally substituted with one or more substituents selected from the group consisting of halogen groups, alkyl groups having from about 1 to 30 carbon atoms and alkoxy groups having from about 1 to 30 carbon atoms;
• (b) reacting said first intermediate with hydrogen or a hydrogen source to form a second intermediate;
• (c) reacting said second intermediate with a hydrogen ion acceptor and compound selected from the group consisting of toluene sulfonyl chloride, benzene sulfonyl chloride, and alkane sulfonyl chlorides having from 1 to about 6 carbon atoms to form a third intermediate;
• and
• (d) reacting said third intermediate with a hydroxyalkylphosphonic acid dialkyl ester compound of the formula ##STR13## where R, R" and M are as described above.