Re-discussion on Hygienic Index and Testing of Printing Ink in Cigarette Printing

Abstract: Hygiene index is an extremely important link for cigarette label printing. How to detect and control is a difficult problem for any ink manufacturer and printer. This article focuses on the detection of hygiene requirements and hygiene indicators for tobacco, and describes methods such as the removal of odors from different perspectives of ink manufacturers and printers.

Keywords: cigarette label printing, ink, hygiene index, detection

Green environmental protection is one of the eternal themes of the tobacco industry. It involves environmental protection technologies, decoration and structural design, material selection, printing processes and technologies, and anti-counterfeiting measures. Looking at the development and changes of tobacco packaging at home and abroad and the survey statistics show that the current development trend of tobacco packaging in the world is mainly reflected in the following three aspects: First, environmental protection, the requirements are to reduce and eliminate the impact on human health and environmental pollution; It is anti-counterfeiting. It is necessary to protect the legal rights and intellectual property rights of famous enterprises, safeguard corporate reputation, establish a good image of the enterprise, and make it easy to identify and reduce the cost of anti-counterfeiting labels. Third, the cost of packaging can be reduced by a variety of ways to offset the cost of packaging. The impact of zero tariffs on foreign cigarette imports.

The "Cleaner Production Promotion Law" passed in 2002 and the newly revised "Environmental Protection Law for the Prevention of Environmental Pollution Caused by Solid Waste" formally stipulated that enterprise products and packaging must meet environmental protection requirements. For the first time, it will prevent environmental pollution caused by excessive packaging and write it into the law, and increase the polluter pays principle and relevant payment regulations. The tobacco industry is currently discussing the revised “General Principles of Cleaner Production of Cigarette Enterprises” and will make clear regulations on the requirements for the environmental protection of cigarettes.

In order to adapt to the global economic integration process and enhance the response capacity of cigarette label printing companies, the state and industry authorities have issued and will soon enter into force a series of policies. The introduction of these laws and policies will surely promote the process of “green packaging” in China. Although ink is not a direct packaging material, it is one of the important components in packaging materials, so it also puts forward hygiene requirements.

The environmental protection of cigarettes is reflected in many aspects. But one of the important indicators is "solvent residue." It has a direct impact on the environmental protection of cigarettes and is the main factor that cigarette companies encounter in the “green trade barriers” of western developed countries in the future.

First, the factors that constitute the smell of paper

As a health index, odor is the first intuitive feeling. The smoke odor is mainly produced by the volatile chemical components that remain in the cigarette pack. After the cigarette pack is printed and processed, it will continue to evaporate, which in turn will produce an odor. The factors such as paper, ink, printing process, finished cigarette label packaging and other factors used in cigarette pack printing and processing are the causes of the odor produced by printed products.

Printing paper consists of plant fibers, excipients, pigments and other chemical additives. The effect on the paper's own odor is the latex in the surface coating (such as the benzene latex in the homemade paper). Other auxiliary additives such as water-repellent agents, lubricants, dispersants, and anti-foaming penalties also have slight effects. When these components are exposed to ultraviolet radiation and high temperature drying, some organic monomers tend to escape and produce a slight odor.

As an ink manufacturer, we can objectively say that the main factors that constitute the non-environmental odor of smoke labels are inks and solvents. The ink used for gravure printing is a volatile drying ink. The binder in the ink is composed of resin and solvent. In the process of evaporation and evaporation of the ink, if the solvent does not evaporate completely, it will cause part of the solvent to remain in the ink layer to generate odor.

First of all, the choice of solvent is an important link, so the first step must be to choose a suitable solvent for environmental protection. The world-famous tobacco group has a clear requirement for the “limitation of smoke labels for solvent residues”. Detailed regulations on volatile substances that are strictly prohibited in the gravure printing products For the volatile substances that are allowed to exist, there are also provisions for limited quantities and variable amounts, and clear provisions are made for the total amount of each square meter. These advanced technical standards undoubtedly point the way for us in the selection of cigarette labels. Second, select the appropriate solvent for the evaporation rate. The same solvent, the lower the boiling point, the faster the evaporation rate. However, when the boiling point of the solvent is different, the volatilization rate is not necessarily close. In this case, when selecting the process, the choice of solvent needs to be very careful.

Secondly, one of the major factors that must be taken into account is the main factors affecting solvent evaporation. In addition to its volatilization rate, the volatilization rate of the solvent is also affected by the resin and the pigment. In general, the more easily the resin dissolves in the solvent, the slower the solvent escapes; the resin with the higher melting point has less solubility and the solvent is more volatile. Therefore, the resin used for high-speed gravure ink should have a melting point of not less than 150°C. However, if the melting point of the resin is too high, the solubility of the resin in the solvent is too low, and other problems may easily arise. The surface characteristics and concentration of the pigment also have an effect on the volatilization of the solvent. The fine particles of the pigment have a small density, and the volatilization of the solvent in the unit area and unit time is less.

Again, the volatilization rate of the solvent is related to the external vapor pressure, temperature, and air volume. Under normal circumstances, the greater the external vapor pressure, the higher the temperature, the greater the amount of air, the faster the evaporation rate of the solvent.

II. Hygiene indicators and requirements for tobacco packaging

The current hygienic requirements for packaging related to ink can be roughly divided into the following three categories. The first category is the detection and control of heavy metal content, ie, the content of harmful heavy metals or toxic and hazardous elements and compounds; the second category is the content of organic volatiles (VOC), that is, the VOC content of inks and prints, and the key organic solvents in packaging materials. The residual content is detected and controlled; the third category is odor, that is, dried printed matter must not contain irritating or even harmful odor.

The first type of heavy metal content can be directly measured, and the point of control lies in the rational choice of controlled elemental compounds. The second type of VOC content needs to be clearly defined in the determination conditions and test methods. The third type of odor cannot be determined quantitatively at present. It can only use scientific statistical methods to express people's average feelings. Although this method does not have clear data, it can also reflect people's subjective feelings to a certain extent.

1, the detection of heavy metal content

At present, the standards for the detection of heavy metal content mainly include the arsenic and lead content specified in the sanitary standard for food packaging paper GBll680-89, and the eight elements content specified in the European Union toy safety standard EN71-3.

The sample preparation of heavy metal content was first allowed to dry naturally at room temperature, and then crushed and filtered through a metal mesh with a pore size of 0.5 mm to obtain at least 100 mg of a solid powder; then 50 times the mass of hydrochloric acid solution (C=0.07 mol/L) was used. L, 37 ± 2 °C) The powder was mixed in a container, shaken for 1 min, its acidity value was measured, and the pH was controlled at 1.0-1.5; the mixed solution was shaken for 1 h under light and 37 ± 2 conditions. After standing for 1 h, the solids were separated from the solution as quickly as possible and filtered out. If necessary, centrifuges could be used, but the centrifugation time should not exceed 10 min. Finally, the obtained solution sample was detected by inductively coupled plasma mass spectrometry. After the measurement data was converted, the data of each heavy metal content was obtained. The result was expressed in mg/kg.

The paper and paperboard (such as smoke) detection process is basically the same as the above process. First, the paper to be tested was sampled at least 100 mg, soaked in 25 times mass of deionized water at 37±2°C to soften and homogenize; then quantitatively transferred to a container and 25 times the mass of hydrochloric acid solution was added ( 0.14mol/1,37% soil 2°C). After shaking for 1 minute, the acidity value was measured and the pH was controlled to be 1.0-1.5. The following process is the same as the above ink process.

2, VOC content testing standards

The current standards for the detection of VOC content can refer to Article 5.8 of China's industry standard gravure composite plastic film ink (QB/T 2024-1994), namely headspace gas chromatography. An FID-type gas chromatograph was used as the measuring device. The cigarette print was cut into a 200-cm2 500-mL flask, sealed with a silicone rubber plug, and incubated in a 50±1° C. incubator for 30 min. The flask was extracted with a 1 mL syringe. The gas was injected into the gas chromatograph to obtain the peak area of ​​each corresponding solvent in the sample. The amount of residual solvent in the printed matter was calculated using various standard solvent curves obtained in advance, and the result was expressed in mg/m<2> , which specifies that the maximum amount of solvent residue is 30 mg/m<2> .

3, odor measurement and control methods

Due to the fact that cigarette odors cannot be quantified at present, scientific statistical methods can only be used to represent people's average subjective feelings. Therefore, they can be roughly divided into five levels. See Table 2 for classification level descriptions. The odor of cigarette packs should be at Level 2 or higher. Although the test results of the residual amount of the solvent in the general smoke label are in compliance with the relevant standards, the odor of the smoke label is objectively present, sometimes reaching a level of 3. This indicates that either the odor has not been detected; or the existing standard is too wide, there will be odor within the qualified range; or the change of factors such as drying of the printed matter affects the size of the odor.

The main reasons for the smoke odor are the following two conditions. The first is the odor of the printed paper itself. The second is the residual odor of the ink (including gloss oil), which can be divided into the residual odor of the solvent and the resin monomer or polymer odor remaining after the ink is cured. In view of this complex and varied situation, it can be considered that the quality and quality of the ink must be improved and controlled from the following three aspects.

(1) The results of the detection of the residual amount of the solvent of the smoke mark and the sensitivity of various commonly used solvents to sensory stimulation, for example, 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 ink improvement is performed, the above solvent is not used or used less, and instead, it is replaced with a low-odor solvent.
(2) Replace the raw materials used in the ink, such as resins, and compare the odors after curing of various types of resins. Use new solvents with good solvent release properties and low odor. However, this must be under the premise of ensuring excellent ink and ink properties. The choice of ink printability will not change.
(3) Since gravure printing must use solvents, the drying process is indispensable: if the drying process cannot ensure that the smoke labels are fully dried, the problem of residual solvents and odors is easily caused, so the printing ink is dried. Confirmation is one of the important means of controlling odors in printing. In general, the temperature of the printing environment is higher for a particular paper gravure ink. 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. At present, the paper gravure ink used is generally under the temperature (25 ± 5) °C, humidity (65 ± 10)% of the printing environment, the printing speed is 80-120m/min, the oven temperature 70-100 °C, can be achieved Most of the drying. The longer the printed matter is stored, the less residual odor will be, under normal circumstances. After reaching 7 days or more, the odor will be substantially eliminated, and the specific data has a greater relationship with the printing variety and printing conditions. $Page break $

Third, measures to improve health indicators

Due to the restrictions on the raw materials commonly used in printing, there is an odor in cigarette packaging printing. In addition to improving the odor of raw and auxiliary materials, combined with the actual production experience of many tobacco trademark printers, in view of the above-mentioned factors unfavorable to the health index, from the perspective of the printing plant, the following measures can be adopted to improve:

1, choose environmentally friendly raw materials. In similar products, use high-quality, relatively environmentally friendly, low-odor paper (such as pure virgin wood pulp or acrylonitrile-emulsion coated paper) and low-toxicity, low-odor, odor-free inks and solvents for production ( Such as environmentally friendly alcohol ink or water-based ink).
2, the design of the product should avoid the impact. In the design of the new cigarette graphic and graphic design, the process of laminating the large area ink should be used as little as possible; as far as possible, materials that can easily increase the odor of the printed product should be avoided.
3. Develop a reasonable gravure printing process. According to different graphics, different materials, different periods of temperature and humidity and other factors, at any time to adjust and improve the printing process, so that easy to produce odor volatile organic components remain as little as possible in the prints. Such as: ink system collocation