Analysing the source of smoke odor from the printing link

With the increasing awareness of environmental protection and the concern for food safety, people have made more and more explicit and strict requirements on packaging materials, especially in the field of food packaging. Although cigarettes do not belong to food, they can make cigarettes smell and affect the health of smokers. Cigarette manufacturers have also put forward various requirements for cigarette packaging materials. The odor of cigarette labels is one of them. The so-called smoke odor is the irritating, even harmful, abnormal odor the smoke mark contains after drying. At present, the smoke odor is generally judged by people's olfactory organs. Although this method does not have clear data, it can also reflect the overall situation of the smoke odor to some extent. It can be roughly divided into five levels: odorless, slight odor, medium odor, strong odor, and extremely strong odor. The quality requirement of smoke odor should be controlled within the secondary standard. If the odor of the smoke mark reaches the third-level standard, it may confuse cigarettes and affect the quality of cigarettes.

There are three main reasons for the odor of cigarettes: the residual odor of the ink, the odor of the printed paper itself, the storage period of the cigarette, and the packaging method. The following specific analysis of these three reasons.

1. The smell of ink residue

The printing methods commonly used in cigarette marking include gravure printing, screen printing, flexo printing, and offset printing. The inks used include solvent inks, water-based inks, offset printing inks, and UV inks. The residual odor of the ink can be divided into the residual odor of the solvent and the odor of the resin monomer or polymer remaining after the ink is cured, and the residual odor of the UV ink. The odor control of the odor can be controlled in four ways.

1) Toluene and butyl acetate itself have a strong odor, and are relatively easy to remain, which easily leads to the generation of smoke odor. Therefore, when the cigarette is printed, the two solvents are not used or used less frequently, and the low odor solvent is used instead. For example, alcohol-soluble or water-based alternatives, especially those that print full-size spot colors, should not use these two solvents as much as possible. In addition, high purity, stable quality solvents should be used.

2) Under the premise of ensuring the ink performance and printability, the use of low-odor and easy-release resin inks will help reduce the odor of smoke labels.

3) The drying process is indispensable because some printing methods must use solvents. If the drying process cannot ensure that the tobacco label is sufficiently dried, it can easily cause residual solvent and odor problems. In general, the higher the temperature of the printing environment, the lower the humidity, the slower the printing speed, the higher the oven temperature, and the smaller the printing area, the easier the ink on the printed matter will be dried, and the smoke odor will be easier to control.

4) Conventional UV inks do not contain solvents, and the oligomers used are generally of high viscosity, and for the purpose of coating, low molecular reactive diluents must be added. They generally have certain volatility and irritation, and are still harmful to the environment. Therefore, water-based UV inks have been developed and developed. They do not need to use reactive diluents to adjust the viscosity, but use water or thickeners to control the rheology of inks. Performance, to solve the volatile and irritation problems, is an ideal environment-friendly product, is the development direction of UV ink.

2. The smell of printing paper itself

Smoke labels usually use white cardboard, gray paper, coated paper, and synthetic paper (including dumb gold paper, glossy silver paper, etc.) We can control the odor of the paper in the following two ways.

1) During the process of pulping, beating and adding fillers, the selected pulping method and filler type may cause odor problems. The most basic quality requirement of consumers for paper jams is that the taste of cigarettes is not affected, that is, cigarettes and paper are not odorized. Therefore, manufacturers of cigarette labels should reach an agreement with the paper production enterprises to adopt advanced pulping methods and choose no stimulation. Filler, to fundamentally eliminate paper odor. Shanghai Tobacco Group has just launched a new era of "Giant Panda" brand. The white cardboard used is a unique four-layer structure of Sweden's Igfondo. It is 100% pure and original, 80 to 100 years old wood pulp, and does not contain toluene. Butyl acetate and hexyl ester will not affect the odor of cigarettes. Tested by the Tobacco Test Center for many times, it will achieve ideal printing quality and prevent counterfeit appearance. In addition, paper is stored for a period of time before it is printed to eliminate odors.

2) Synthetic paper is a layer of synthetic film (aluminum foil, aluminized film, etc.) on the basis of cardboard. The type of adhesive selected and the drying method used may cause odor problems on the paper. If a slow-drying adhesive is used, the drying speed is slow and the paper is prone to odor. Of course, the drying method is also an influencing factor.

3. The smell of cigarettes caused by the storage cycle and packaging methods

The longer the cigarette label is stored, the less residual odor will be. In general, after a period of time, the odor will be substantially eliminated. The specific data has a greater relationship with the printing variety and printing conditions. According to the actual situation, it is empirical data. In addition, the method of cigarette labeling will also affect the odor of cigarette labels. As far as possible, full-size field products should not be sealed and sealed with plastic bags, and kraft paper with good air permeability can be used to facilitate the distribution of the odor of cigarette labels.