Discussion on Solvent Residues in Composite Packaging
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The composite packaging refers to a packaging material of a printing ink film (such as BOPP, PET, etc.) which has a physicochemical protective property which cannot be attained by a substrate in which the amount of the adhesive is not adhered by the resin. Generally used for food packaging, with the improvement of environmental protection safety awareness and food packaging (color retention and taste) in recent years, the quality control requirements for solvent residues in composite packaging bags are more and more strict, and printing and packaging manufacturers and packaging bags use customers. Both are looking for ways to reduce solvent residues.
The solvent residue of the composite packaging is sampled immediately after printing. The test method and standard are in accordance with the national standard document: GB/T10005-1998 biaxially oriented polypropylene/low density polyethylene composite film, the total solvent residue is less than 10mg/m2, of which benzene Party class but less than 3mg/m2.
Solvent residues in composite packaging are generally produced in inks, solvents, and manufacturing processes. The quality of the ink, the drying speed of the diluent solvent, the performance of the machine, the environment, and the packaging structure all affect the solvent residue. Since the domestic composite packaging printing is mainly based on gravure rotary printing, the ink is designed in the form of benzene and ketone, and the solvent is volatilized to dry. The ink generally contains unequal amounts of toluene, methyl ethyl ketone and ethyl ester. When the solvent is used, the molecular weight and boiling point of each solvent are different, and the volatilization speed is also different, which causes the various solvent residual values to be different.
So what are the factors that affect solvent residue? The following analysis will be from the ink, solvent, environment, composite packaging structure:
1. Composite ink Generally, the chlorinated polyolefin and polyester resin are the higher the absorption residual amount of the resin molecules in the main binder, and if the solvent is poorly released, a large solvent residue is formed. In general, polyester inks have better solvent release properties than polyolefin inks.
2. One of the biggest reasons for solvent residue is the influence of solvent performance. The quality of the solvent itself, the water content, the boiling point, and the evaporation rate will be 10 million solvent residues. If the solvent in the ink contains high hydrazine, the high water content will be high. The drying rate is reduced, and the detection of the quality of the solvent is formed, so as to have a quality problem.
3. The permanent residue is not a single cause. The drying system temperature, wind speed and air volume of the printing machine often affect the solvent factor, but the wind speed and air volume can not keep up, the solvent residue will be the same, and it will be particularly obvious on the high-speed printing machine. In addition, the printing workshop environment and air flow will also have a certain impact.
4, in the packaging structure, there are many ways to reduce the solvent residue supervision method using co-extruded film, to focus on benzene-free composite ink or alcohol-soluble composite ink, choose environmentally friendly solvent, use solvent-free composite or extrusion compound, etc. .
The composite package itself is more controlled in a more complicated printing process, or it can control the solvent residue.