Analysis of common problems in gravure printing

Q: How to improve the adhesion of gravure printing ink?
answer:
1, first of all to determine the ink is printed on what substrate, due to the great difference in adhesion of ink on different substrates, generally based on the printed substrate choose the right polyamide resin, can be selected by experiment, can also be used YMT polyamide resin.

2. The adhesion of the ink produced with polyamide resin on BOPP film is general, this problem can be solved by adding BK-515 aldehyde and ketone resin (BK-515 itself has a lot of polar genes, and can perform well with BOPP film. The attachment is generally 2% to 8% of the formulation.

Q: How to reduce the amount of solvent residue in food packaging printing?
answer:
Solvent residue problem has always been a difficult problem for ink companies. The state has already required the residual amount of benzene solvents to meet the hygiene requirements of BOPP/PE compound packaging, which must reach 3mg/m2 or less, with the continuous demand for food hygiene. To improve, how to reduce the amount of solvent residues in food packaging and printing has become a key issue for ink companies.

According to our understanding of the situation can be reduced from the following aspects of food packaging printing solvent residue:

1. In EVA-40W, MP-45, and CL-PP resins, CL-PP always has the highest residual solvent and EVA-40W has the least residual solvent, so it can guarantee the composite strength. Under the conditions, the content of CL-PP can be reduced and the content of EVA-40W can be increased.

2. Select the appropriate CL-PP. Different manufacturers of CL-PP in the complex ink caused by the difference in the amount of solvent residue, if the formula cost can be accepted, you can choose the production of Japanese paper
PP803MWS can generally be reduced to 50% under the same amount of conditions;

3. When dissolving EVA-40W, MP-45 and CL-PP, add a part of ethyl ester and residual solvent reducer (0-Sol??ventm), which can effectively reduce the residual of toluene solvent in the ink film. the amount;

4. Check whether the solvent used for the ink and the solvent used for printing are pure. If there is a small amount of high-boiling solvent, it may cause the solvent residue to be too high, and even lead to serious odor in the printed matter;
5, in the process of printing and compounding:

1 Minimize the use of toluene solvent when preparing the dilution solvent, and use a mixed solvent of toluene, acetic acid and methyl ethyl ketone = 2:5:3;

2 in the printing process to improve the printing machine drying tunnel exhaust, appropriate to increase the temperature of the drying tunnel, if conditions permit, after the white ink is printed, open the drying tunnel for multiple drying;

3 The viscosity of the ink can be properly reduced during the printing process.

Q: How to solve the problem of reverse printing in the printing process?
answer:
Anti-envelope printing is particularly noticeable at low to medium speeds. The phenomenon of reverse printing at high speeds is greatly reduced. The key to solving the problem of reverse printing is to analyze the reasons for clear printing. In reverse printing, the ink is generally printed before the ink is reversed. On the printing plate of the ink, it enters the ink tank of the posterior color, changes the color of the ink of the latter color, finally causes the printing to be unable to continue, if the yellow ink gradually turns into the light green color, the red ink turns into the purple color gradually.

Generally can be solved from the following aspects:

1. Adjust the proportion of the ink color dilution solvent to reduce the ability of the color ink to dissolve the ink of the preceding color when it comes into contact with the ink of the preceding color. That is, when diluting the color ink, add a part of isopropyl alcohol and try to use less toluene. ;

2, increase the speed of printing

Increasing the printing speed can significantly reduce the contact time between the back color ink and the front color ink, which is particularly obvious in reverse printing at low speed printing, and there is basically no reason for reverse printing in high speed printing. This may be limited by the printing equipment and the printing environment during actual printing;

3, adjust the formula composition of printing ink

First of all, you can use the method of improving the adhesion of the ink on the BOPP film, so that when the two inks are in contact, the ink of the front color is still attached to the BOPP film. In the ink of the CL-PP system, the CL-PP can generally be increased. Content is solved.

Secondly, the drying speed of the ink of the preceding color can be increased, the temperature of the drying path of the ink of the preceding color can be increased, and the presence of a small amount of non-volatile solvent in the ink ink film can be prevented.