With the improvement of people's living standard, to food packaging also put forward higher request ink in the packaging is especially remarkable. Ink as printing materials, should satisfy all sorts of different functional requirements, such as non-toxic, heat resistance, cold resistance, solvent resistance, oil resistance, resistance to friction and resistance to radiation, etc. Internationally recognized food printing ink used must abide by the principle of no transfer; Food packing printing surface shall not be used in conventional ink; Print manufacturer must ensure that all the solvent after printing ink and toner calls for volatile, and achieve application cured thoroughly the corresponding standards of industry. Therefore, in food packaging and printing ink role sensational. Below from food packaging inks used in the printing to characteristic, the way, print material to illustrate.
Benzene soluble chlorinated polypropylene ink is currently the most extensive use face is mainly used for food plastic packaging and printing inks. These ink both manufacturing and use technology has matured, mainly used for BOPP (two-way stretch polypropylene) material, but also adopted gravure printing way. Although the ink printing eligibility fine, postpress performance is good, quick drying, but because the relative bigger toxicity, toluene solvent residual value printed high; And because the poor thermal stability of chlorinated polypropylene in production and process of storage, easy release chlorine and the formation of hydrogen, make the ink is strong acidic, to print roller have serious corrosion problems, so that the ink tend to be eliminated. Because people have realized benzene soluble ink can damage the ozone layer, in use process will also to workers' health and safety causing harm, and remain in the residue packing products, with a certain conditions will cause for packing of food in a degree of pollution. So in Europe and some developed countries have successively formulated a banned the use of aromatic solvents or control ink. Therefore, the development accord with environmental and food hygiene requirements ink is imperative problem.
Environmental printing ink should be both wrong, and no environmental pollution harm the body operating workers, but also not damage the food is installed inside.
1. The water-base printing ink
Water-based ink is most at home and abroad and the gravure packaging printing office, and it mainly consists of water-soluble ink resin, organic pigments, solvents and related auxiliary after composite grinding and into. Water soluble resin is the link expected, ink domestic often choose water-soluble acrylic modified resin for links, its heat-resistant material, permanent, chemical resistance, resistance to pollution and glossiness have significant advantage of scattered, whether directly or synthetic polymer emulsion, dissolved all represent excellent performance and water-based ink excluding volatile organic solvent residual, not only can reduce the toxicity, and designed to prevent electrostatic and flammable solvent for contact and misfire, is a new type of "green" printing ink. Water-based ink is also replace benzene soluble ink in the best products.
2. Ultraviolet (LIV) curing inks
Uv curing inks refers to uv light in certain wavelength of the radiation within the ink feeding some cross-linking reaction links to shift from liquid to solid, curing inks, it completed before feeding dissolve in links, macromolecular pre-polymer namely firmly form ink film.
Uv curing inks is mainly used for soft, flexible printing substrate by pre-polymer, reaction diluent, pigment, additives, photoinitiators/synthetic composition. Which reactive diluent choice the migration of ink formula influence; the reaction Additives on the properties (ink printing eligibility, ink, base material of migrating the wetting, friction coefficient, wear resistance, pigment dispersion and stability) and prints smell adjusting; Requirements of uv absorption spectra of pigment scope as small as possible. The ideal pigment should have good dispersion, softness good, strong tinting, in light ultraviolet absorption of tiny, for polymerization without impairing etc. Characteristics.
Use uv solidifying ink printing should pay attention to the polymerization inhibition, surface tension and viscosity of wet function, ink with humidity correlation, print expansion, etc. Due to adhesion of plastics ink to bad, so for the printing plastic flame treatment or corona discharge processing, in order to improve the plastic surface adhesion.
3. EB curing inks (EB ink) EB curing inks refers to the high-energy electron beam under the irradiation of can quickly shift from liquid to solid inks, also called EB ink. Electron beam energy of pigment and packing high, such solid component has a strong penetration, won't appear ink was pigments or packing obstacles, ink film absorbed by the internal dry won't be affected. EB composed mainly of ink pigment, links materials, auxiliary agents, for ink by electron beam to realize curing the material choice of, so links have specific requirements, the main component of the resin and acrylic class is the active monomers in response.
Food and beverage packaging industry most adopts eb curing for offset printing, printing way. EB high-speed printing industry ink adapt once, multicolor printing development direction. In the 1980s abroad already development application, domestic in recent years began to applications. Due to save energy electron assimilation ink solvents and is not included in components of environment, packaging no pollution, curing time is short, the processing speed, high output, dot enlargement rate is minor, imprinting brightness is good, have wear-resisting and chemical resistance, so the advantages of erosion by rapid popularization and application technology, especially in food packaging field broad prospect of application. EB curing inks ink and LIV major difference is that whether any links to material photoinitiators, when EB add a certain amount of light ink initiator, also can undertake ultraviolet curing. EB curing thicker can be the ink layer,
Because the printing ink need not photoinitiators, cost relatively lower than LIV ink, but eb curing equipment investment higher than LIV curing.
4. Digital printing ink
Digital printing technology is increasing as people opposite permeates the individualization packaging needs of food packaging and printing industry. Adopting digital printing technology can reach a high enough image resolution, can ideal ground emersion the detail of the image.
Additionally, digital printing technology can provide more efficient small batch service. Digital printing ink printing method to take the different can be divided into: ink-jet printing ink, electrostatic printing dye the solid dye and digital offset electronic gravure ink, etc. Pigments are by melting heat by ceramic crystals in print materials after the heat. Print materials for metal aluminium foil, mostly, PET (ep), paper etc, and suitable for printing paper rolling. Dye chooses appropriate fuser temperature is very important, because the best fuser temperature can easily control pigments fuser process. Pigments should have certain flexibility, facilitate print materials processing. Fold Solvent resistance digital printing for electrostatic is also extremely important, solvent resistance printed will be unable to complete the bad after procedure, such as glazing, drugs, etc.
In the green environmental protection and safety of food packaging requirements, high quality, multicolor printing today, the printing ink also should adapt to the development of The Times, without benzene turn toward the direction of development, environmental protection.
