| 摘要 |
An adhesive, which becomes tacky on heating and remains so on cooling, and comprising a thermoplastic resinous material and a thermoplastic plasticizer is immediately set to a non-tacky state, after fusion and subsequent cooling to below the fusion point of the plasticizer, by distributing the same plasticizer over the cooled adhesive in finely divided solid form. The resultant set adhesive, which may be in the form of a film on a supporting surface, may be rendered tacky again by fusing the adhesive as required and the cycle may be repeated, 3-20 per cent. added plasticizer is usually sufficient. Adhesive compositions in examples include ethyl cellulose mixed with tri- (para-tertiary butyl phenyl) phosphate or dicyclohexyl phthalate plasticizer, and ethyl cellulose compositions having N-ethyl para-toluene sulphonamide or triphenyl phosphate plasticizer mixed with rosin, or coumarone-indene resin, or modified rosin ester and hydroabietyl alcohol. Other compositions are polyvinyl butyral composition having N- ethyl paratoluene sulphonamide or a mixture of o- and ptoluene sulphonamide plasticizer and including polymerized rosin, or maleic alkyd-modified rosin ester and hydrogenated methyl abietate. Powdered silica may be added to the plasticizer to prevent agglomeration. |
