Лако-красочные материалы — производство

Hot melts have gained ground because they provide for high production speeds. EVA copolymer-based hot melts are commonly used for the unsewn binding of magazines and catalogs, although other thermoplastic polymers are also used on occasion. In order to adjust the hot melts to specific properties they are mixed with resins and waxes. As with waterborne adhesives, hot melts are generally applied via roller application.

In recent years, low-temperature hot melts processed at temperatures ranging between 120 °C and 140 °C have become popular in the graphics industry. As with hot-melt packaging adhesives, their main advantages are low thermal stress, im­proved viscosity and color, longer service life and less equipment maintenance and energy consumption. Because the difference between processing temperature and room temperature is low, setting is commonly very rapid. This property is a major advantage for three-side trimming in the case of short cooling lines and high processing speeds, because it helps to reduce wrinkling, and the knifes will become coated with adhesive. Another advantage of a low application temperature is that local drying out and curling of sensitive paper, or paper that is inappropriately grained, is reduced and the paper more quickly recovers its equilibrium moisture content.

However, when the application temperature is close to the room temperature the adhesive molecules may have less time to wet the paper surface and this may impair adhesion. For papers that are difficult to bond, it is advisable to perform a test prior to production to ensure correct adhesion. Another parameter that must be tested is that of thermal endurance.