Лако-красочные материалы — производство

Adhesives for remoistening applications such as tapes, stamps, labels, and envelope flaps must be capable of rewetting. Such adhesives should also be glossy, noncurling, and nonblocking under humid conditions. This requires that the formulation contain acid — modified starch or high-soluble white and yellow dextrins to allow a high solids content. A plasticizer is added to prevent brittleness in the final film. In tape and stamps, the paper with adhesive has traditionally been run over a bar to produce microcracks in the adhesive layer, thus rendering it noncurling. A similar effect has been achieved by solvent deposi­tion of the adhesive. In this process, a cold-water-soluble dextrin is suspended in an organic solvent, where it is insoluble. When this suspension is applied to paper and dries, it leaves behind a layer of discrete dextrin particles, which will not curl. Formulations for two remoistening adhesives are given in Table 6.