Patent ID: 8609789

Claim:
A halogen-free, oligomeric or polymeric phosphonic acid comprising units of formula (I) —[(O) m —{R 1 (X) n (Y) o } p R 1 (X) q ] r —[(O) s —R 5 (X) t ] v — (I), where: X is —P═O(OH) 2 , Y is carbonyl or sulfonyl, R 1 , R 5 are, independently of one another, divalent or polyvalent, substituted or unsubstituted, heteroatom-free aromatic radicals, m, o, s are each 0, n, q, t are each, independently of one another, 0 or an integer from 1 to 8, with n and s not simultaneously being 0, r, v are each, independently of one another, from 0 to 1, with the sum of r and v being from 0.95 to 1.05, and p is 0 or an integer ≧1, where the radicals X are substituents on R 1 and R 5 , and R 1 and R 5 are directly bonded to a phosphorus atom through an aromatic group, wherein repeating units of formula (I) are bonded to one another in the form of a polymer or oligomer chain.