| abstract |
An acrylic acid polymer having a weight average molecular weight M w in the range from 3500 to 12 000 g/mol and a polydispersity index M w /M n ≤2.5, wherein 30％ to 60％ of the acid groups of the acrylic acid polymers have been neutralized with calcium ions, 30％ to 70％ of the acrylic acid polymers have been neutralized with sodium ions and 0％ to 10％ of the acid groups of the acrylic acid polymers have not been neutralized. |