Cigarette Pack Printing Industry: Mandatory Standard on Solvent Residues Takes Effect

According to a report from the Tobacco Bureau: against the background of society's growing concern about the safety, hygiene and environmental protection requirements of consumer goods, the State Tobacco Monopoly Administration has issued a mandatory industry standard on limits for solvent residues in tobacco packaging: "Limits of Volatile Organic Compounds in Cigarette Carton and Box Packaging Paper", and for the implementation of this limit standard it has formulated the corresponding testing method: "YC/T207-2006 Determination of volatile organic compounds in cigarette carton and box packaging paper — Headspace-gas chromatography".

The implementation of the mandatory standard for solvent residues places higher requirements on the cigarette packaging printing industry, and also has far-reaching significance for promoting the development of the papermaking, printing and ink industries in the direction of environmental protection.

Tobacco packaging technology has always led the trend of domestic printing technology development. The implementation of the solvent residue standard is an urgent subject for the printing industry on how to achieve compliance with VOC residue limits through strict quality control measures, and how to improve the printing process, improve the printing environment and strengthen inspection methods will all be contents included in this subject. I believe that through the efforts of people in the industry, China's printing industry will surely be brought to a new stage.

For ink suppliers, water-based gravure cigarette packaging inks have been talked about for several years now, some ink companies have already been cooperating with printing companies on development, and a few cigarette packs have already achieved gravure printing with water-based inks. Now, the implementation of the solvent limit standard will certainly promote the application of water-based inks in the field of cigarette packaging printing. How to develop water-based inks with better printing performance and realize the industrialization of water-based inks in the field of cigarette packaging printing will be a very real goal, and this will play an important role in promoting the upgrading and replacement of the domestic gravure printing ink system.

Since the release of this limit standard, tobacco companies in various places have attached great importance to it and have successively required cigarette label printing units to carry out self-inspection work, rectify problems in a timely manner, make preliminary preparations for the formal implementation of the standard, and strive to achieve the goal of 100% pass rate in spot checks by the State Tobacco Monopoly Administration. In my view, cigarette packaging printing companies should start from the following aspects to take countermeasures:

1. Equip with precision instruments for VOC testing.

Since the State Tobacco Monopoly Administration requires the implementation of a strict testing system for tobacco packaging, once a situation of containing "benzene" or exceeding the total solvent content is found, mandatory measures such as scrapping the packaging products will be implemented. Therefore, only by equipping corresponding precision instruments to test the VOC content can printing and packaging companies avoid the serious losses brought by blind production and shipment.

1. Grasp the relationship between printing press speed and solvent residue.

The printing of cigarette labels generally involves very large batches, while delivery deadlines are often very short. Therefore, achieving high-speed printing can not only improve production efficiency but also ensure timely delivery. However, in the high-speed printing process, the printed part per unit area passes through the oven for too short a time, and once the oven and air-blowing devices fail to meet requirements, the solvent residue often exceeds the limit. We suggest that printing companies choose a suitable printing speed according to their own actual situation to ensure that the solvent residue meets the standard.

1. Control the purity and type of diluting solvents.

The choice of diluting solvent is also closely related to printing speed, but under the requirements of the limit standard, it is necessary to abandon the previously commonly used solvents such as butyl acetate, isopropanol and n-butanol, and instead use more environmentally friendly solvents such as n-propyl acetate, n-propanol, propylene glycol methyl ether and anhydrous ethanol, and the specific proportions can be adjusted according to different ink systems.

1. Actively trial-use fully alcohol-soluble inks and water-based inks.

The implementation of the solvent residue limit standard will rapidly promote the development of fully alcohol-soluble inks and water-based inks. As for the solvent-based cigarette packaging inks currently dominated by NC systems, although they can also reach the VOC limit standard through strict index control and adjustment of the printing process, their solvent residue is greatly affected by weather, the printing environment and various printing auxiliaries, so many uncertain factors will inevitably arise, bringing greater difficulty to VOC control.

In comparison, the advantages of fully alcohol-soluble and water-based inks become evident. In the printing process of fully alcohol-soluble inks, anhydrous ethanol alone can be used as the diluting solvent; while water-based inks only need an appropriate amount of ethanol added during printing to adjust the drying speed, and no other toxic or harmful organic solvents are used, greatly reducing the possibility of VOC exceeding the limit. Therefore, the replacement of existing solvent-based inks by fully alcohol-soluble inks and water-based inks will become an inevitable trend.

In solving the problem of VOC exceeding the limit, our company has communicated and been in contact with printing customers many times and learned about the problems found and solutions adopted by some printing enterprises in their self-inspection work to meet the standard. They are summarized below for reference by friends in the industry.

Problem 1: A printing company found excessive benzene after testing with a GC-3061C gas chromatograph, but after testing the ink, paper and diluent, no benzene solvent was found.

Analysis: After investigation from many sides, it turned out that the supplier providing the diluent had packed a drum that had once contained benzene as ethyl acetate and supplied it to the printing company. At that time the solvent in that drum had been used up, while the solvents in the other packaging drums had no such problem. After the printing company required the solvent supplier to supply in drums, the problem of excessive benzene in testing no longer occurred.

Solution: Containers used repeatedly must be strictly controlled, with dedicated drums for dedicated use.

Problem 2: A printing company in Henan, in its printing production process, had a printing speed generally below 150 m/min and used large amounts of butyl acetate as diluent in the ink. Subsequent testing with a GC-3061C gas chromatograph showed that butyl acetate exceeded the limit by about 17 times, but the measured value of propylene glycol methyl ether was only 0.3, far below the limit standard of 60.

Analysis: Because butyl acetate has a relatively slow volatilization speed, it is very prone to residue, and the limit data for butyl acetate in the limit standard is 5, which is relatively strict. Slow-drying solvents with smaller limit values should be avoided.

Solution: This customer chose ethyl acetate and propylene glycol methyl ether in a ratio of 8:2 for printing, which both ensured the printing effect and brought the test data within the requirements of the limit standard.

Problem 3: A printing company in Hubei, when producing with a gravure printing press, had a printing speed reaching 230 m/min and basically adjusted the oven temperature to near the high setting of 110 degrees, but the samples submitted for testing still showed an ethanol content exceeding the limit by about 2 times.

Analysis: In gravure solvent ink systems, ethanol has a relatively fast volatilization rate and belongs to the fast-drying type of solvent, so under normal circumstances it is not prone to leaving large amounts of residue. The crux of the problem of exceeding the limit is that the oven temperature of the printing unit was too high, causing the solvent in the inner layer to be inhibited from volatilizing after the surface layer dried, resulting in the phenomenon of fast-drying solvent exceeding the limit.

Solution: This customer adjusted the temperature of the printing units so that the temperature formed an increasing gradient from the first unit to the last unit, and at the same time increased the air-blowing force, effectively solving the problem of ethanol exceeding the limit.

Problem 4: A printing company in Jiangsu, during production, used the solvent ratio recommended in Problem 2 as the diluent. After printing, testing with a GC-3061C gas chromatograph found that propylene glycol methyl ether exceeded the limit by about one time.

Analysis: Propylene glycol methyl ether has a slow volatilization speed, and if its amount can be limited to within 20% of the diluent, it generally will not exceed the limit. Later, the propylene glycol methyl ether used by this customer was analyzed with a GC-3061C gas chromatograph, and its purity was found to be only about 75%.

Solution: Switch to the same type of product produced by a regular manufacturer, and the test data met the requirements. Therefore, in the process of using various solvents, suppliers must be required to provide purity analysis reports.

The GC-3061C gas chromatograph is an analytical instrument with relatively high cost performance. The instrument adopts microcomputer control, keyboard operation and Chinese menu display on a liquid crystal screen.

It has high integration of electronic circuits, good reliability, simple operation, memorized setting parameters without the need to set them again each time, and it is suitable for long-term continuous operation. The large column oven and large fan, together with an automatic rear-door-opening cooling system, increase the cooling speed of the column oven and truly realize operation at 5℃ above room temperature. It adopts a large-screen liquid crystal Chinese display. Operation is convenient and easy to learn. Automatic electronic ignition function.

It has self-diagnosis, over-temperature power-off protection, file storage, recall, five-stage programmed temperature rise and other functions, and has a single-column automatic compensation function; it can ensure the stability of the baseline during programmed temperature rise analysis.

The instrument is equipped with dual packed columns and three injection ports for capillary columns, with independent three gas paths.

It has six independent temperature control zones and an intelligent rear-door-opening system, and the cooling speed is very fast; the vaporization chambers, detectors and amplifiers all adopt modular design, making installation and replacement very convenient;

It is equipped with a separate and complete capillary analysis system and an independent capillary split injector (including septum purge, split and make-up gas adjustment). An optional capillary split/splitless injector is available.

The instrument is equipped with five types of detectors: hydrogen flame detector, thermal conductivity detector, flame photometric detector, electron capture detector and nitrogen-phosphorus detector. Three detectors can be installed at the same time, and users can choose and equip them according to their own analysis requirements; they can also add a six-way valve injection, a conversion furnace device and so on; and series and parallel operation of detectors can be realized.

——This article is reprinted from China Packaging Network (pack.cn), original link: http://news.pack.cn/show-362256.html