(Barrier Coatings for Paper: Uses, Compositiona, and Hot Melts)

The selection of hot-melt adhesives, coating devices, and the conditions under which water-based coatings are applied on the corresponding paper substrates are all very important parameters that can enhance the operational properties and appearance of packaging prints, such as the gloss of packaging prints. Degree, water resistance, oil resistance, stain resistance, abrasion resistance, light resistance, and durability of protection of printing colors, etc., thereby improving the decorative effect and use value of prints.

The performance of paper (especially kraft paper) varies greatly. The main performance parameters of paper include: Quantitative, Thickness, Porosity, Smoothness, Gloss, Surface Strength, Size, and Cellulose Content. When the paper needs special treatment or finishing, these parameters will have an effect on the final treatment effect. In order to control the influence of these parameters, corresponding measures need to be taken. Water-based protective coating is one of the methods.

Protective layer characteristics Paper is a cellulose-containing, hydrophilic substrate material that absorbs moisture, oil, and grease. Uncoated paper has a relatively high water vapour transmission rate and is prone to "hygroscopic" and "wetting" phenomena. Fast food boxes, packaging of meat, fish and poultry, packaging of pies, and packaging of machine metal parts require that they must have a certain resistance to oils and greases, as well as a low air permeability, to prevent the contents from being The deterioration of air or water through the deterioration or corrosion. Therefore, in response to the above requirements, the protective layer came in handy and played its corresponding role. In addition, these performance indicators are also critical and very important for the packaging and printing process. At this time, the use of a water-based protective layer can help us to solve these challenges and difficulties.

Composition In order to ensure the necessary barrier and protective properties of the paper, a high molecular polymer was used to make a water-based protective coating. We all know that most of the polymer films formed have water resistance, oil resistance and grease resistance, and can prevent the moisture in the paper fibers from evaporating. Some polymers have a chemical structure that effectively repels the ingress of moisture, grease, and oil. The polymer film layer also improves the smoothness of the paper surface. A small amount of defoamer and auxiliaries to improve the fluidity are also added to the waterborne paint, as well as a certain amount of pigment (colorant). These auxiliary additives all have an effect on the performance of the protective coating and can also improve the performance of the protective coating.

Water-based protective layer and hot-melt adhesive Generally, the water-based protective layer can prevent the hot-melt adhesive from infiltrating into the paper fiber, so that it has an adhesive property. Coatings that are most difficult to bond with hot melt adhesives are those that have oil and grease resistance, so they are often used as a release layer.

The choice of adhesive is very important. In order to make the hot melt adhesive easier to apply, the parameters that need to be changed are: melting point, melt viscosity, and heat capacity or gel length. Hot melt adhesive coating equipment is also very important, reasonable coating thickness, adhesion properties on the paper coating surface are all very important factors.

Conclusion Since paperboard and packaging printing companies are constantly improving the added value of their products, the use of water-based coatings to achieve the protective properties, the value is simply not measured. Careful selection of substrate materials, coatings, hot melt adhesives, and equipment parameters can result in a successful combination that greatly broadens the scope of paper.

By understanding the nature of these parameters, the operator can determine and specify how to solve the problems and faults caused by improperly set printing parameters, such as failures caused by substrates, materials, equipment, auxiliaries, and coatings. The main contents involved include: plastic film, metallized film, aluminum foil material, paper, test, corona and ozone treatment, EDM treatment and desiccant, primer and its type, ink, water-based paint and adhesive. , solvent-based coatings and adhesives, solvent-free coatings and adhesives, extrusion coating resins, heat-sealing resins and heat sealing, coating and coating equipment, extrusion coating equipment, and unwinding/rewinding, cutting Wait.