Process for the purification of polyol PFPE derivatives

A process for the purification of a polyol(per)fluoropolyether derivative [polyol (P)] from a mixture of hydroxyl(per)fluoropolyether derivatives [mixture (M)],

• said polyol (P) comprising one or more hydroxyl(per)fluoropolyether derivatives [PFPEs (OH)] comprising at least one (per)fluoropolyoxyalkylene chain (chain Rf) and at least one end-group having formula (t3):
• —CF2CH2OCH2CH(OH)CH2OCH2CH(OH)CH2OH
• said mixture (M) comprising said polyol (P) and at least one hydroxyl (per)fluoropolyether derivative [PFPE (OH)], said PFPE (OH) being different from said polyol (P) and comprising at least one (per)fluoropolyoxyalkylene chain (chain Rf) and at least one end-group selected from the group consisting of end-groups having formulae (t1):
• —CF2CH2OH and
• end-groups having formula (t2) —CF2CH2OCH2CH(OH)CH2OH,
• said process comprising the following steps:
• step 1:
• reacting said mixture (M) with a ketone, an aldehyde, or a combination thereof so as to yield a corresponding mixture of cyclic ketal/acetal (per)fluoropolyether derivatives [PFPEs (OH)p] [protected mixture (P)];
• step 2:
• submitting the said protected mixture (P) to adsorption on a silica gel so as to yield an adsorbed protected product [adsorbed product (Pp)] and then recovering a desorbed protected product [desorbed product (Pp)] by subsequent desorption from said silica gel of said adsorbed product (Pp);
• step 3:
• distilling the said desorbed product (Pp) under reduced pressure so as to isolate a protected product residue [product (Pr)];
• and
• step 4:
• hydrolyzing the said product (Pr) so as to obtain said polyol (P).