The packaging and printing industry is developing rapidly in the direction of rapid, multi-color, and one-time printing. UV inks and UV varnishes have become the new favorite of packaging and printing materials. However, with the time of application and the increasing application field, people have put forward newer and higher requirements for the above products: not only do not dry on the printing press, but also quickly dry after printing; both require low cost of materials It should have high gloss; it should have long storage period and good adhesion after printing and roller coating.
At present, few can meet the above requirements at the same time. Packaging and printing operators are concerned about the adhesion fastness of the printing ink film and roller coating film, followed by the ability to flow at low temperatures without agglomeration.
Regardless of whether it is UV ink or UV varnish, the packaging and printing plant is afraid of operating in the season with high temperature and high humidity; second, it is afraid that the moisture content of the substrate exceeds the standard. Because after printing or glazing on the above-mentioned workshop environment and substrate, it is very easy to pull the ink film or adhesive film off when it is initially tied (tape paper), and it is returned by the user. For example, the author found in the “Shuanghui†group in Luohe, Henan: The group ’s ham sausage carton was packed and sealed with adhesive tape. When the tape was peeled off during consumption, the decoration (ink and varnish) on the packaging seal was pulled away in pieces. , Reduced the quality of the packaged goods (surface) view, directly damaging the brand image of the enterprise. Another example is Nanjing Gold Foil Group's printing of the mouth flower on Wuhan Jinlong cigarettes. When automatic labeling is performed at 140 ℃ ~ 160 ℃ at high speed, it is often difficult to label in the continuous labeling process, or it is not resistant to high temperature or is cut off when cutting Printed graphic color blocks ... This not only affected the reputation of the Gold Foil Group with a certain reputation, but also increased the scrap rate for users.
The above ink and varnish are peeled off due to the difference in adhesion strength between them and the substrate. How to improve the adhesion strength.
The author has conducted surveys in Yiyang, Hunan, Shanghai Pudong, Zhangjiagang, Jiangsu, Wuxi, Xinxiang, Henan, Xingyang, Qingdao, Shandong and other places. Combining the experience of previous years, I have visited seniors in the printing industry. From the analysis of different brands, technical parameters and actual ratios of photocurable resins or prepolymers to crosslinking agents, from photosensitizers to polymerization inhibitors, it is believed that some existing manufacturers have neglected the role of crosslinking agents, an ideal The crosslinking agent is also an ideal reactive diluent, not only miscible with wax, but also capable of dissolving and diluting unsaturated polyesters and resins, reducing the viscosity of ink and varnish systems, and improving the fluidity of inks and varnishes. And can participate in the photo-curing reaction, so it is often less in its formulation, which results in poor ink flow and lumping and non-freezing of the varnish; the second is that the amount of photosensitizer is too large. The main light curing speed is actually not the case. A large amount of use can not only increase the light curing speed, but also increase the production cost accordingly. Excessive photosensitizer will reduce the strength of the conjunctiva of the UV open car or UV varnish. And on-site preparation of new materials and production process adjustment, trial, application method comparison, light intensity and light energy record of the photochemical reaction process, curing speed and workshop environment temperature and humidity control, substrate PU value and different moisture content (1 %, 2%, 3%, 5%, 6%, 7%, 8%) After comparison, it is found that whether it is alcohol sol or polyvinyl chloride primer, the moisture content of the cardboard of the substrate is controlled at 3%, so It is said that the printing UV ink and roller UV varnish have poor adhesion due to poor fluidity and agglomeration, which are all related to the water content. Improve the adhesion strength of the ink film. One is to replace with new UV ink and UV varnish. The second is to add 3% to 6% of the JS-PPH (302) film-forming aid of Shanghai Jinshan Chemical Plant to the ink or varnish. Agent, or add 0.2% ~ 0.5% of JS-F4011 adhesion promoter or 5% ~ 15% of CH3COOC2H5, which can ensure that the adhesion strength of ink film and varnish film of packaging and printing is fundamentally improved.
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