sents an integer of 1-4 and preferably 2-4, and when m is an integer of 2, 3 or 4, the two, three or four R2 and R3 groups may be the same or different], and (b) reaction products of titanium alkoxides of general formula (I) above with aromatic polyvalent carboxylic acids represented by the following general formula (II): [wherein n r