Cation Exchange Resin: Phenol Sulfonated and Cured with Formaldehyde (Wassenegger and Jaeger, I.G., US 2,204,539)

A water softener needs a solid that holds sodium loosely and calcium tightly. Wassenegger and Jaeger put sulfonic acid groups on phenol first and then cured it with formaldehyde into a hard resin, so every unit of the resin carries an exchange site. Charged with salt water it holds sodium, and gives it up for calcium. Result: a dark, hard cation exchange resin in the sodium form; Example 1's resin takes up to 5 % of its weight of lime. Source: Wassenegger and Jaeger, US 2,204,539 (I.G. Farben, 1940), Examples 1-2. Not given: formaldehyde strength in Example 2. Picture drawn by Youblob.