| 摘要 |
A packaging material laminate has an inner layer of RF energy absorbent material, e.g. an EVA containing more than 15%, preferably 18-28%, of vinyl acetate, a first outer layer of heat-sealable material substantially less absorbent of RF energy e.g. EVA containing less than 15%, preferably 4 to 9%, of vinyl acetate, and a second outer layer also of substantially less RF absorbent material and preferably of higher-melting material, e.g. high density polyethylene. Thus portions of the material can be superimposed with the polyethylene layers outermost, and clamped between RF welding jaws. Irradiation heats the intermediate layers, which heat the adjacent EVA outer layers, which are urged to seal together to form a package. The polyethylene does not melt, and so is readily separable from the jaws. The package interior is of EVA with only a low content of vinyl acetate, which will neither affect nor be affected by the package contents. |
