Biocidal glass additive for marine paints

Claim 1

Finely divided particles of glass suitable as a biocidal additive to coatings subjected to marine environments exhibiting a rate of solution in sea water such that biocidal metal ions are released at a rate of at least 10 mg/m 2 of surface area/day, said glass having a composition selected from the groups consisting of SiO 2 -based glasses and B 2 O 3 -based glasses, said SiO 2 -based glasses consisting essentially, as expressed in weight percent on the oxide basis, of about 30-65% SiO 2 , 10-25% R 2 O, wherein R 2 O consists of 0-25% Na 2 O, 0-25% K 2 O, and 0-10% Li 2 O, 0-15% BaO, and 0-50% CuO + ZnO + SnO 2 consisting of 0-50% CuO, 0-35% ZnO, and 0-20% SnO 2 , the copper reported as CuO being present in the glass as Cu + ions, at least 10% CuO being present unless the sum of ZnO + SnO 2 exceeds about 30%, and said B 2 O 3 -based glass consisting essentially, as expressed in weight percent on the oxide basis, of about 40-65% B 2 O 3 , 5-15% Al 2 O 3 , 0-15% R 2 O, wherein R 2 O consists of 0-15% Na 2 O, 0-15% K 2 O, and 0-10% Li 2 O, 0-15% BaO, and 30-50% ZnO + SnO 2 consisting of 10-35% ZnO and 0-20% SnO 2 .