Polyvinylene carbonate and polyhydroxymethylene, processes for their preparation and their use

A polymer consisting substantially of a base polymer which comprises units (II) or a mixture of units (I) and (II) containing more than 50% by weight of units (II) based on said mixture, said units (I) and (II) having the following structural formulas ##STR4##

• in which R.sub.1 and R.sub.2 are hydrogen or a monovalent hydrocarbon radical with up to 8 carbon atoms, which polymer also contains up to 30% by weight, based on the base polymer, of covalently bonded units which are derived from at least one compound of formula (III) ##STR5## and are grafted onto the base polymer in which:
• R.sub.3 is a hydrocarbon radical with 4 to 30 carbon atoms;
• X is a member selected from the group consisting of --O--, COO-- and mixture thereof;
• R.sub.4 and R.sub.5 are hydrogen or a monovalent hydrocarbon radical with 1 to 8 carbon atoms, with the proviso that at least one of the radicals R.sub.4 and R.sub.5 is hydrogen;
• m is an integer from 1 to 40;
• and
• n is an integer from 1 to 4.