Synthetic polyamides and their salts

A compound of formula I, or salt form thereof ##STR46## in which each R.sub.1, independently is selected from hydrogen, carboxyl, amino or a group of formula .alpha.

• -A.sub.1 -R.sub.10 (.alpha.)
• each R.sub.2 independently is hydrogen or a group of formula .alpha.;
• A is a bridging group of the formula -CO-NR.sub.3 -, -NR.sub.3 -CO- or ##STR47## A.sub.1 is a bridging group;
• n is 0 or 1;
• R.sub.3 is hydrogen, C.sub.1-12 alkyl or a group R.sub.10 ;
• R.sub.4 is a group R.sub.10 or a group of formula .alpha., ##STR48## R.sub.5 is hydrogen or C.sub.1-12 alkyl;
• each R.sub.10, independently, is a group of formula (a), (b), (c), (d) or (e) ##STR49## R.sub.11 is hydrogen or C.sub.1-4 alkyl;
• each R.sub.12, independently, is C.sub.1-5 alkyl;
• each R.sub.13, independently, is hydrogen, C.sub.1-2 alkyl or one group R.sub.13 is phenyl and the other R.sub.13 is hydrogen or C.sub.1-2 alkyl or both groups R.sub.13 together form a group of the formula -(CH.sub.2).sub.11 -;
• Y is -N-CO- or -CO-N- wherein one of the two free valence bonds attached to each nitrogen corresponds to the free valence bond attached to Y in formula (c);
• p is an integer from 5 to 200;
• with the proviso that the compound of formula I contains 1-400 sterically hindered amine groups;
• or a salt thereof.