Hydrophobically modified polyamine scale inhibitors

A method of treating scale in a process stream comprising:

• intermixing with a process stream a composition comprising a polymeric reaction product of a polyamine, a first nitrogen-reactive compound, and a second nitrogen-reactive compound, the polymeric reaction product having a weight average molecular weight of at least 500,
• wherein the composition is present in an amount effective to reduce or eliminate scale in the process stream,
• wherein the first nitrogen-reactive compound comprises a —Si(OR)3 group and a nitrogen-reactive group, wherein R is H, optionally substituted C1-C20 alkyl, optionally substituted C6-C12 aryl, optionally substituted C7-C20 aralkyl, optionally substituted C2-C20 alkenyl, Group I metal ion, Group II metal ion, or NR14, wherein each R1 is independently selected from H, optionally substituted C1-C20 alkyl, optionally substituted C6-C12 aryl, optionally substituted C7-C20 aralkyl, and optionally substituted C2-C20 alkenyl;
• wherein the second nitrogen-reactive compound comprises a nitrogen-reactive group and does not contain a —Si(OR)3 group;
• wherein at least one of the polyamine and the second nitrogen-reactive compound comprises an optionally substituted hydrocarbyl radical comprising from 2 to 40 carbons;
• and
• wherein the process stream comprises at least one of a sulfate level of at least 1 g/L, a iron oxide level of at least 20 mg/L, a sodalite level of at least 20 mg/L, and a combined nitrate/nitrite concentration of at least 0.5 molar.