Hygienic requirements for food packaging inks

With the rapid development of the packaging industry, people have made more and more explicit requirements for packaging materials, especially in the field of food packaging. Cigarettes, like foods, are closely linked to people's daily lives. Cigarette manufacturers have also put forward various requirements for cigarette packaging materials. 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 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. Measurement and control methods of different enthalpies

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.

3.1 Odor source analysis and ink improvement method

There are mainly two kinds of reasons for the odor produced in cigarettes. (1) The odor of printed paper itself. (2) Residual odor of ink (including gloss oil) can be divided into residual odor of the solvent and 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) As for the detection results of the smoke standard solvent residue and the sensitivity of various commonly used solvents to sensory stimulation (see Table 2), it can be seen that toluene and butyl acetate itself have stronger odors and are more likely to remain, which may easily lead to Smoke odor produced. 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 7 days or more, the odor will be substantially eliminated, and the specific data will have a greater relationship with the printing variety and printing conditions.

Source: China Ink Technology Network