Adhesive dispensing solvents for packaging adhesives

　　Due to the chemical characteristics of polyurethane adhesives, the use of solvents containing water, alcohols, amines, esters and other solvents containing active hydrogen or reactive groups is not permitted in the preparation of the adhesive, but only inert solvents such as esters, ketones, hydrocarbons (alkanes or aromatic hydrocarbons) with a high degree of purity should be used, and also consider the hygiene and safety of the product and the avoidance of odours and smells.
　　Toxic aromatic hydrocarbons such as toluene, xylene should be used as little as possible, the heavy odour of methyl ethyl ketone (i.e., the next ketone) should also be used sparingly, and these problematic solvents are best not used. In the case of having to use, it is necessary to work on the drying, to ensure that they evaporate as much as possible clean, as little residue as possible.
　　Economically developed countries on the packaging materials, health performance, odour, smell is very sensitive to the slightest problem can not pass. Therefore, if used for the packaging of export products, special attention should be paid!
　　In the export of products, often due to the packaging material itself in the residual solvent content of aromatic hydrocarbons is too high, loaded into the food, it is through the inner layer of material migration to the food, food adsorption, resulting in food odour or toxicity, foreign countries can not be accepted and was returned.
　　Sometimes also encountered such a problem: composite pouches at room temperature do not smell odour, but when the bag is still with the heat of the food (such as just made from the processing line to bake a good biscuit), to be cooled down and then tasted the food, there is an unpleasant odour, which is due to the temperature is high, to promote the migration of residual solvents.
　　This odour problem is often caused by more than just the adhesive and the solvent it is used in, as many factories only use ethyl ester ethyl ester solvents, but there is also toluene residue on the bag. Butanol or xylene odour odour, which is the original cause of the printing ink. Now the composite printing ink, most of the use of “composite ink”, both the so-called “printing ink”.
　　This ink in the use of solvents, in addition to ethyl ethyl ester, there are butanone, xylene, butanol and other high-boiling point odour and toxicity of the solvent.
　　As the pigment particles in the ink is very small, the specific surface area is very large, the adsorption capacity is very strong, although in the printing has been heated and dried, but because of the short time, fast speed, often drying is not complete, too much residual solvents, especially in large areas of more than one set of prints, but even more so. These residual solvents brought to the composite process, the composite is more difficult to run off, had to slowly migrate penetration, so there will be the above problems.