In the winding process you can use an inner ply adhesive, an outer ply adhesive, or a universal glue for both plies: special blends of our brands Enziflex and Dextrolin.
There are 3 ways of tube winding: straight, conical and spiral winding. The tube winding process is as follows. First, ranging from 2 to max 30 cardboard plies are glued together, depending on the desired tube wall thickness and strength. These are spirally wound on a mandrel and fastened by means of 1 or 2 rubber belts. Thereafter the tube is cut to the desired length.
Tube winding adhesives
The crush value (the force required to crush the tube) of the tubes is strongly influenced by the type of paper and the number of plies. Nevertheless, the type of adhesive can also have an influence on the crush value. Crush values are determined after thorough drying of the tubes.
The tubes must have a high initial strength otherwise deformation occurs during the stacking and the storing of the tubes. The initial strength is dependent on the moisture content of the tube and the setting speed of the adhesive.
Tube winding adhesives can be applied by means of rollers, a cascade system or a dipping tray.
Four types of adhesives
Four types of adhesives can be used for tube winding:
- PVOH dispersion based, with or without filler
- dextrin based in liquid form
- water glass based (sodium disilicate) either pure or modified
Polyvinyl acetate (PVA) dispersions are fast setting and have a high solid content. PVOH (polyvinyl alcohol) dispersion adhesives often give a flexible adhesive film whereby a good sealing but a lower crush value is obtained. Dextrin adhesives have a high wet tack and a high solid content. The setting speed of these adhesives is in general slightly lower than that of PVOH dispersion adhesives. Dextrin adhesives give a hard adhesive film.
Water glass (sodium disilicate) is not a true adhesive but more a product that fixates the plies in relation to each other. A high degree of sealing is not usually attained with water glass, however, high crush values are. By modifying water glass, an endeavour has been made to combine the advantages of the above types of adhesives: a high crush value for the tube, a good sealing and rapid bonding.
Polyvinyl alcohol (PVOH) adhesives are still applied by some customers. The glue film is hard and the adhesive has a high wet tack. Water glass is only suitable for the inner-plies. Due to the minimal wet tacking strength it cannot be used for the outer-plies. If the water glass is applied to the inner plies by means of a submersion bath, this means that the adjoining paper plies cannot be glued using a standard PVOH adhesive because coagulation occurs as soon the latter comes into contact with the water glass.
Sometimes an outer ply is glued with a dextrin glue or dextrin glue is used (single-sided) on the second to last ply and PVOH glue to the last ply. As the latter results in extra time handling, Paramelt has developed a PVOH adhesive that is allowed direct contact with water glass.
Properties for the inner and outer plies
Tube winding adhesives must fulfill the following general properties for both inner and outer plies:
- ensure good adhesion of paper to paper (paper can have both a very open structure or a very closed structure)
- if the adhesive is applied to a single side, then there must be a good transfer to the dry paper plies (no excessive diffusion of the adhesive into the cardboard)
- to keep the moisture content of the tubes as low as possible, a high solid content is an advantage
Paper swells under influence of moisture. It is therefore important to apply a minimal amount of water to keep the shrinkage of the tube to a minimum.
Inner-ply adhesives: if the adhesive is applied by means of submersion, then there must be low penetration into the paper.
Outer-ply adhesives: the adhesive must have a high wet tack or must set quickly, otherwise the tube ends will start to open upon cutting.