Лако-красочные материалы — производство

On a quantity basis, the most important paper product bonded with adhesives is corrugated board (Figure 8.23), which is a very important material for the production of shipping containers.

The development of the corrugated board industry began in 1874 when a patent was issued in England describing the bonding of a flat linerboard to a fluted corrugated sheet to generate a material with excellent cushioning effect that was preeminently well suited as a packaging material. The first adhesives used for the bonding of corrugated board were conventional paper glues, such as a mixture of cereal flours and water. Due to the large amount of adhesive needed for this application, its commodity price has in the past played an important role, besides its technical properties. In 1939, the Stein Hall glue was invented; this was an adhesive system based on starch which made it possible to considerably increase the efficiency of corrugated board production. Stein Hall corrugating adhesives are a mixture of fully gelatinized starch, available as a colloidal solution, with native,

ungelatinized starch dispersed in water. This combination makes it possible to obtain high-solids adhesive formulas, without increasing the viscosity to such an extent that the adhesive can no longer be processed on the roller application system. Unfortu­nately, in this state the adhesive does not have a satisfactory adhesive property for bonding. Following its application, during compression ofthe corrugated board, the adhesive layer is heated for a short period to such an extent that the dispersed native starch gelatinizes. This results in a steeply rising viscosity which allows the freshly bonded corrugated board to resist the forces occurring in the further production process. With starch-based adhesives, excellent technical properties can be combined with a low price, and the production of corrugated board has therefore become the most important field of application of natural polymers in adhesives (see Section 5.9). Currently, corrugating adhesives are undergoing continued development to cope with ever-advancing manufacture technologies. The trend towards faster production speeds requires the constant adaptation of technological parameters of adhesives such as viscosity, gelatinization temperature and initial ‘tack’ [28].