Diester of carboxymethoxy benzophenone and Poly tetra- methyleneglycol 250;alpha-[2-[(9-Oxo-9H-thioxanthenyl)oxy]acetyl]-omiga-[[2-[(9-oxo-9H-thioxanthenyl)oxy]acetyl]oxy]poly(oxy-1,4-butanediyl);Polybutyleneglycol bis(9-oxo-9H-thioxanthenyloxy)acetate