Method to reduce the rate of diffusion of slow-release materials through polymers and process for making drip irrigation devices with long-term control of root growth

Abstract

A method for reducing the rate of diffusion of a slow-release material through a host polymer material to increase the useful life of a slow-release product. An inert fine particulate inorganic material such as an intercalation material having a layered structure is incorporated into a mixture of the slow-release material and the host polymer. The intercalation material has its layers intercalated with molecules of the slow-release material which are accommodated within spaces between the layers of the intercalation material. The particulate material slows the diffusion rate of the slow-release material through the host polymer when compared with the diffusion rate of the same slow-release material through the same host polymer not containing the particulate material. In one embodiment, the intercalation material comprises a nano-clay, the host polymer is a polyolefin, and the slow-release material is a bioactive material such as dinitroanaline. The slow-release product can comprise a drip irrigation emitter device or tube or tape or device used adjacent to an emitter to protect against root intrusion. The intercalation material can comprise a layered nano-clay produced by contacting the clay with a surface modifier to achieve sorption and complexing of the surface modifier between adjacent spaced layers of the clay material, sufficient to expand the spacing between adjacent platelets. This is followed by exfoliating the surface-treated material to separate the platelets, followed by mixing the exfoliated platelets with the polymeric material to form a polymeric matrix from which drip irrigation products can be made.