Dispersible ionomer powder and method of making the same

A method for making a powdery material [material (P)] composed of a plurality of particles of at least one ionisable polymer comprising a plurality of ionisable groups selected from the group consisting of —SO3Xa, —PO3Xa and —COOXa, whereas Xa is H, an ammonium group or a monovalent metal [ionomer (IX)], said method comprising:

• Step (1):
• providing an as-polymerized aqueous latex [latex (Ip)] comprising particles of at least one ionomer precursor comprising a plurality of hydrolysable groups selected from the group consisting of —SO2XX, —PO2Xx and —COXx, whereas Xx is a halogen, in particular F or Cl [precursor (IP)];
• and
• Step (2):
• contacting said as-polymerized aqueous latex [latex (Ip)] with a basic hydrolysing agent [agent (B)], in conditions to at least partially convert said groups —SO2XX, —PO2XX and —COXx, whereas Xx is F or Cl, into corresponding groups —SO3Xa, —PO3Xa and —COOXa, whereas Xa is H, an ammonium group or a monovalent metal, without causing any significant coagulation, so as to obtain an aqueous latex of particles of ionomer (IX) [latex (Ix)];
• optionally, Step (3):
• contacting said latex (Ix) with at least one ion exchange resin, so as to at least partially remove residues of agent (B) and/or other contaminants;
• and
• Step (4):
• spray drying the latex (Ix), possibly after purification, so as to obtain the said material (P).