| 摘要 |
A method of preparing a remoistenable starch-based adhesive coating is disclosed. A starch having a low amylose content and/or which has been chemically treated so that it gives an aqueous phase of suitable viscosity and which has a long-term stability over at least a week, is selected. The aqueous phase is then added to a solvent phase, which comprises a polymer emulsion, or mixture of at least two polymer emulsions, in toluene. The polymers are typically selected from the polymers classes of ethyl or methyl methacrylate/2-ethyl hexyl acrylate copolymers and polyvinyl proprionate. The polymer emulsions act to sterically stabilise the aqueous phase globules in the solvent phase, and also act to control the viscosities of the aqueous and solvent phases. Once the viscosities are controlled, a flash evaporating agent such as methyl oxital is added and the phases are mixed to produce aqueous phase globules of a suitable particle size for coating substrates such as gummed paper and postage stamps, The mixture is then diluted with an aliphatic hydrocarbon solvent and is then coated onto the substrate. When the diluted mixture dries on the substrate the methyl oxital flash evaporates resulting in pores on the adhesive coating which facilitates evaporation of the solvents. The coating on the substrate is then a remoistenable starch-based adhesive. |
