Top Tack Info
Protein adhesives
Protein adhesives are made of gelatine, a product made out of the lower skin layers of hide, a leftover from the leather processing industry. Because of its high polymer structure, the protein adhesive forms a physical bond, and thus develops fast and high tack. High initial and final tack Protein adhesives are the sole adhesives with the capability to jellify. Applied at a temperature of approx. 60°C the jellification point will be reached when cooling. Then the adhesive jellifies and passes from the liquid to the solid state. During this transition, the protein adhesive develops extremely high tack, and this leads to fast adhesion with high initial tack, called top tack. When the water proportion enters the material to be glued (the substrate), the adhesive concentrates and enhances its tack. The water evaporates. Additional physical bonds are formed, providing a final tack which is even higher than the initial tack. Thanks to this feature, the laminated material can be processed very soon after application. Improved evenness Protein adhesives offer obvious benefits in the evenness of laminates: when compared to PVAc- dispersions, approx. 40 percent less water has to be applied into the laminating materials during the adhesion process. Recyclable In the graphics industry, the recyclability of the applied products is a market-winning benefit. Protein adhesives are a great contribution: they are not poisonous, they are recyclable and they are biodegradable. Thanks to the water solubility of protein adhesives, there is no risk of stickies in paper recycling as is the case with most hotmelts. Processing machines can be cleaned easily with hot water. Protein based adhesives are proof against ethereal oils and almost all solvents, and they are heatproof up to approx. 200°C. This not only makes them the most widely used adhesives for bookcover production, it also makes them suitable for ever more applications as packaging adhesives.
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