Inhibiting scale in vinyl monomer polymerization

A solution comprising

• (A) water;
• (B) about 0.01 to about 6 wt % of a terpolymer that comprises the condensation reaction product of
• (1) an aromatic compound selected from the group consisting of compounds having the general formula
• (2) about 0.1 to about 5 moles per mole of said aromatic compound of a carbonyl compound selected from the group consisting of compounds having the general formula
• where n is an integer from 1 to 10;
• and
• (3) about 0.1 to about 5 moles per mole of said aromatic compound of a thiourea having the general formula
• where R is hydrogen, alkyl from C1 to C15, or aryl, alkaryl, or aralkyl from C6 to C15, each R1 is independently selected from the group consisting of OH, R, SO3R, and CO2R, each R2 is independently selected from the group consisting of R1, SH, SR, haloalkyl from C1 to C15, alkoxyaryl, naphthyl, and polycyclic aryl from C6 to C15, and each R3 is independently selected from the group consisting of NH2 and R2;
• (C) about 0.5 to about 2 wt % sodium hydroxide;
• (D) about 8 to about 10 wt % sodium chloride;
• and
• (E) 0 to about 20 wt % methanol or ethanol.

A method of making a terpolymer comprising the condensing, in the absence of an acid catalyst,

• (1) an aromatic compound that contains a benzene or naphthalene ring substituted with the group OR or SR, where R is hydrogen, alkyl from C1 to C15, or aryl, alkaryl, or aralkyl from C6 to C15;
• (2) about 0.1 to about 10 moles per mole of said terpolymer of a carbonyl compound per mole of said aromatic compound;
• and
• (3) about 0.1 to about 10 moles per mole of said terpolymer of a thiourea per mole of said aromatic compound.