Preparation of type A zeolites for use as desiccants in polyurethane compositions which have improved water absorption capability and do not absorb and then release nitrogen

摘要

A method of preparing type A zeolites with Si/Al atomic ratio 0.95-1.1 with the total of cationic sites occupied by sodium, calcium and/or magnesium, potassium and hydronium cations and comprising, in equivalents, 10-69% sodium ions, 28-55% potassium ions, 2-45% calcium and/or magnesium ions and 1-20% hydronium ions. The zeolite is prepared by contacting: an aqueous suspension (a-i )of zeolite 3A (a-1), 4A (a-2) or 5A (a-3) with an aqueous solution (b-j) of calcium (b-1) or potassium (b-3) salts or solutions of salt(s) of calcium and potassium (b-2) and with an acid solution (c). Contact is either simultaneously a-i, b-j and c; or a-i and b-j then c; or a-i and c then b-j; or b-j and c then a-i. In all cases i and j are identical. The solid obtained is filtered out, washed, dried and activated, preferably by sweeping with a non-degrading gas.