the reactive group being an acryloyl group, a quaternised or non-quaternised aminoalkyl carbonyl group or a (—N)n—CO—A—O—X or (—N)n—CO—A—Hal group, wherein A is an alkylene or alkylidene group, X is hydrogen or an acyl radical of an organic or inorganic acid, Hal is a halogen atom, and n is 0 or 1
