The representative product of the substitute alkali for the phosphate system is Alkaflo developed by Sybron. The Morran patent provides a specific method for the substitute alkali for this system, and different raw materials can be used to prepare lye with different pH values. The main components of high pH lye are tripotassium phosphate, potassium hydroxide, and sodium hydroxide (the amount is small, the purpose is to improve the stability of the lye to temperature, you can choose not to add it). The main components of low pH lye are sodium dihydrogen phosphate and phosphoric acid. If high and low pH lye are mixed in different proportions, a series of lye with different pH values can be obtained. Adding borate, ethanolamine, etc. to the lye can improve the buffering capacity of the system. The ethanolamine can be monoethanolamine, diethanolamine, triethanolamine or a mixture thereof.
When preparing lye with high PH value, the dosage of tripotassium phosphate is 20%-50%, potassium hydroxide is 2.5%-20%, if you choose to add sodium hydroxide, the dosage is 0.4%-7%, ethanolamine is 4% ～8%, borax pentahydrate is 4%～10%. When preparing low pH lye, sodium dihydrogen phosphate is 13%-40%, phosphoric acid is 0-30%, and ethanolamine is 1.9%-4%. The patent points out that the amount of lye in the dye bath is 0.1% to 0.3%.