preparations for the control of parasites

摘要

1521938 Controlled release antiparasitic preparations SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ BV 23 Aug 1976 [25 Aug 1975] 34984/76 Heading A5B A controlled release antiparasitic composition comprises (a) a compound of formula: wherein the two R radicals are the same or different and each is C 1-10 alkyl, X is oxygen or sulphur, Y is hydrogen, chlorine or bromine and hal is chlorine or bromine, (b) a homo-carbon-carbon addition polymer of molecular weight 5000 or more and (c) a styrene/maleic anhydride or styrene/maleic acid copolymer, of molecular weight from 2,000-800,000, containing 0-20% of maleic ester residues and having 1 to 4 styrene residues per maleic residue the composition comprising particles of component (b) having a porosity of 0.15 to 0.70 cc/g and a particle size of 30-200 mesh (USS) coated with component (c), component (a) being partitioned between core and coating, the weight ratio (a) : (b)+(c) being not more than 1:5 and the weight ratio (b) : (c) being from 1:4 to 1: 1.5. Preferred organophosphorus compounds are dimethyl 2, 2-dichlorovinyl phosphate and methyl octyl 2, 2-dichlorovinyl phosphate. The homopolymer (b) may be polyvinyl chloride.