Side seam adhesives can be applied by means of a contact roller system or by contact free spraying system.
Side seam adhesives must fulfill the following general requirements:
- ensure good bonding of paper to paper (sometimes the paper contains a difficult glue inner or outer print or a layer of varnish);
- the adhesive may not cause the discolouring of the envelope (migration of ink from inner- or outer print);
- if the adhesive is applied by means of roller or segment gluing, it must not splash or spray;
- if the adhesive is applied by means of spray equipment, it must not exhibit tailing or satellite building;
- good roller stability.
The adhesive may not thicken too much in the glue container.
Due to the evaporation of water and the forming of foam in the glue, the viscosity (apparently) increases. This influences the splashing behavior and the yield of the adhesive.
