Printing ink sticky back is not complicated, composite membrane is not puzzled

Plastic sheeting or transparent paper printing after the mark has been dry, but in the printed after reel or bag storage period has appeared on the back of the sticky dirty phenomenon, serious when broken between calendar does not open, figure ink layer dye migration, caused the product scrap. This kind of phenomenon occurred more often in high temperature season, but high temperature is not the only cause of back stick, it also with plastic, printing ink, solvent evaporation rate, the air volume, light and a series of factors of operating environment has the close relation. The links of a, printing ink resins used in printing ink link material resin, ink adhesion resistance is different also. The currently used plastic film gravure ink all belong to solvent-based inks, by connecting material resin, pigments, solvents, etc. As a link of material resin, ask its bonded to solid and printing film, printing adhesion after winding, has certain softness, and ability of high temperature, in a certain range is not affected by external factors change. Link material softening point of the resin directly affects the performance of the printing ink layer. Link material softening point of the resin is too low, can make the printing ink layer under the environment of high temperature is slightly molten state, so that the printing product adhesion in the aftermath of the winding. Improve connecting material softening point of the resin, apparently to prevent adhesion, but high softening point, printing ink layer of flexible bending sex will become worse, easy to brittle fracture. Commonly used polyamide with PE, PP film table printing ink, for example, the ink link for polyamide resin, generally are of low molecular weight linear polymers, is made up of dimer acid and alkyl ( Or aryl) Diamine polycondensation, its softening point usually is 100 ~ 110 ℃. Under normal circumstances, in order to meet the needs of the printing or considering the economy, when printing in the printing ink often to be in a mixed solvent. Each link of material has its own true solvents, solvent, the solvent. The better solubility, it means the link is the greater the affinity between the resin and solvent molecules; And the better solvent on solubility of the resin, resin on the release of the solvent is the worse. Release the sex difference, will directly cause the below mentioned problem of residual solvents. Therefore, in the preparation of mixed solvent, solvent should be controlled in a certain range. Should not only consider the ink printing eligibility requirements, as well as considering the composite solvent release. For a link to a similar type of resin material, the lower the softening point of the resin, also means that the resin is more easily dissolved, resin solvent will be worse off. From this aspect consideration, also should accordingly improve the link material softening point of the resin. In addition, when processing and printing ink, if the grinding time is too long, produced by the grinding temperature is too high, lead to link material resin part degeneration, will also bring certain influence to the adhesion. Second, gravure ink after printing was not completely volatile solvents in printing ink transferred to the plastic film, printing ink layer on the surface of the solvent will be the first to evaporate, whereas in printing ink layer internal solvent must spread to infiltrate ink membrane surface, and then to evaporate and dry. When printing ink layer drying into the end stage, printing ink film surface already cured, this limits the printing ink layer internal continued to spread and evaporation of the solvent, resulting in the issue of residual solvents. Plastic film is by solvent evaporation to dry ink printing. The volatile rate is decided to ink layer drying conditions and the important factors that affect the printing quality. Solvent evaporation slower, the version of the reproducibility is better, print color more beautiful, but easy adhesion; On the other hand, will produce the phenomenon such as mark white. So, choose the suitable solvent volatilization rate, is the key to the plastic film gravure printing. In continuous chromaticity printing, film between two printing stations running time, must finish all volatile solvent, otherwise, the next station when printing, will glue roller. Film printing, printing ink in the organic solvent in the drying system has not been completely volatile, still have after film winding waste heat, to the residual solvents in the ink layer brings to volatile conditions, and form adhesion. After high temperature and wet season, printing film winding too tight or compression. When printing ink layer in the residual solvents reaches a certain concentration, printing ink layer keep micro melting ( Wetting) State, which directly led to the adhesion problem. So we must to control residual solvent quantity of them. Plastic film gravure printing with solvent, give priority to with alcohols, benzene, alcohol use ethanol, isopropanol and benzene class multi-purpose toluene, xylene. As a result of the need of nitrocellulose, also want to join esters, such as ethyl acetate, butyl acetate. In short, makes every effort to ink in the volatile organic solvents before winding from it completely. Appropriate slowed down and increase the air volume. Film printing, loosely put inside wire woven baskets, dry ink layer to ventilation, curing after cutting, bag making, film printing bag, after the bandage, vertical in cartons, reducing the pressure between the membrane surface. Three, the printing ink adhesion fastness of the printing ink layer adhesion fastness of also has a close connection with adhesion. Poor printing ink layer adhesion fastness, it is easy to make the printing ink film under the condition of stress transfer to another layer in contact with membrane, resulting in adhesion. So we must ensure good ink adhesion fastness. The causes of ink adhesion fastness bad are the following points. 1, whether the wrong with ink, or a mixture of different kinds of ink. 2, plastic film corona processing bad or excessive moisture absorption. The additives precipitation in 3, plastic film, or air is dust adsorption onto the membrane, which affect the printing ink adhesion. 4, ink, bleaching and metamorphism. 5, poor drying. Source: plastic flexible packaging interaction