Cross-linked Poly(4-vinylpyridine) -Bromine Complexes as Preserving Agent for Fruit and Vegetables

Abstract

With the aim of developing preserving agents (ethylene-removing agents) for fruit and vegetables, the synthetic conditions and the properties of poly (4-vinylp3rridine) resins and resinbromine complexes obtained were investigated. Polymerization of 4-vinylpyridine with divinylbenzene as a cross linking agent was conducted in aqueous suspension systems, in methanol dispersion systems, and in aqueous systems added with some organic solvents. Resins of large granular size with considerable strengths were obtained in aqueous suspension systems. However, the specific surface areas of the resins were very small. In methanol dispersion systems, although resins of large specific areas were obtained, the granules were fragile and troublesome to handle. With the addition of t-pentyl alcohol and toluene to aqueous dispersion system, porous resins were obtained having sufficient size and strengths of granules for practical use. In this aqueous systems with t-pentyl alcohol and toluene, a part of divinylbenzene could be replaced with styrene and the resins of lower cost were obtained.1, 2-Dibromoethane was detected when a 4-ethylpyridine bromine complex as a model for the poly (4-vinylpyridine) bromine complex was brought into contact with ethylene gas. Poly (4-vinylpyridine) resins effectively adsorbed 1, 2-dibromoethane. Thus, it is suggested that the removal of ethylene by the resinbromine complex is due to the adsorption of 1, 2-dibromoethane, which is produced by the addition of bromine in the complex to ethylene. In addition, the rates of ethylene removal by the resinbromine complexes increased as the specific surface areas of the resins increased. This result indicates that the rate-determining step of the reaction is the diffusion of ethylene into the inside of the poly (4-vinylpyridine) bromine complexes.