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L. Szosland, A. Połowińska, A. Pierzchlewska, S. Połowiński


Production of biocide-containing polymeric microspheres by solvent evaporation from polymer emulsion and release of biocides from microspheres into water media

Polimery 1993, No 3, 107


DOI: dx.doi.org/10.14314/polimery.1993.107

Summary

The solvent-evaporation microencapsulation process was used to prepare spherical polymeric microcapsules in the range of particle size between 5 and 80 pin. Microspheres were obtained in watcr-in-oil emulsion in which the continuous phase was a silicone oil and the discontinuous phase – a mcthanolic solution of ethyl cellulose (EC), butyrylchitin (BC), polyvinylpirrolidone (PVP) or poly(methyl methacrylate-co-dimethylaminoethyl methacrylate) (PMMDM, a Eudragit-typc copolymer) containing 6—18 mass-% of trichlorophenol or salicylic acid as a biocide. Biocide release from polymeric microspheres under perfect sink conditions into water or dilute aqueous solutions of hydrochloric acid was investigated. A simple exponential equation Mt/Ma = 1 - c_(L,+I') was used for the description of biocide release kinetics (М,/Мш is the fractional biocide release, к and b arc constants). Previously [10–14] we reported that this equation describes well the biocide release kinetics from microsphcrcs of crosslinked dextrane swelled with water. It was shown now that this relation can also adequately describe the rate of biocide release from non-swelling in water polydisperse microspheres of EC and BC. The rate of biocide release is slightly affected by the type of polymer used, but it is controlled by the diffusional and dissolution mechanisms of biocide release. The rate of biocide release from microsphcrcs soluble in release medium (PVP and PMMDM) depends on the rate of polymer matrix dissolution. The change of pH value of the medium from 3 to 7 leads to a 50-limes slower biocide release from microspheres made of PMMDM. Salicylic acid releases from the non-swelling EC microspheres with a higher rate than trichlorophcnol, probably due to a better solubility in water of the first biocide.


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