Mandatory Solvent Residue Standard for Cigarette Packaging Printing: VOC Control and Eco-Ink Transition Accelerate

Reports from the tobacco authority indicate that, with consumers paying closer attention to safety, hygiene and environmental performance, the State Tobacco Administration has rolled out a mandatory industry standard limiting solvent residues in tobacco packaging: 'Limits of Volatile Organic Compounds in Cigarette Carton and Box Packaging Paper'. A supporting test method was also established: 'YC/T207-2006 Determination of Volatile Organic Compounds in Cigarette Carton and Box Packaging Paper — Headspace-Gas Chromatography'.

The mandatory solvent residue standard raises the bar for cigarette pack printing and is expected to have a lasting impact by steering papermaking, printing and ink supply chains toward greener operations.

Cigarette packaging technology has long set the pace for China's printing advancements. With the solvent residue standard in place, the industry now faces an urgent question: how can rigorous quality control keep VOC residues within limits? The answer covers print process improvements, better shop-floor conditions and stronger inspection systems. Industry-wide efforts are expected to lift China's printing sector to a new level.

For ink suppliers, water-based gravure inks for cigarette packs have been discussed for years. Some ink makers have already partnered with printers on development, and a small number of cigarette packs have been gravure-printed with water-based inks. The solvent limit standard should accelerate water-based ink adoption in cigarette packaging. Developing water-based inks with better printability and commercializing them in this segment is now a practical goal, and it will play a key role in upgrading and replacing China's gravure ink systems.

Since the standard was released, tobacco companies across regions have placed strong emphasis on compliance. They have asked cigarette label printers to run self-inspections, correct issues promptly and prepare for full implementation, with the aim of achieving a 100% pass rate in spot checks by the State Tobacco Administration. In my view, cigarette packaging printers should take action in the following areas:

1. Equip precision instruments for VOC testing.

The State Tobacco Administration enforces strict testing for tobacco packaging. If benzene is detected or total solvent content exceeds the limit, the packaging can be scrapped under mandatory measures. Printers and converters therefore need suitable precision instruments to measure VOC levels, avoiding severe losses caused by blind production and shipment.

1. Understand the link between press speed and solvent residue levels.

Cigarette label orders are usually large and delivery windows are short, so high-speed printing can improve efficiency and help meet deadlines. However, at high speed, the printed area spends less time in the dryer. If the dryer and air-blow system underperform, solvent residues can exceed limits. Printers are advised to choose a suitable speed based on their own conditions to keep residues compliant.

1. Control the purity and type of dilution solvents.

Dilution solvent choice is closely tied to press speed. Under the limit standard, printers must move away from commonly used solvents such as butyl acetate, isopropanol and n-butanol, and shift to more environmentally friendly options including n-propyl acetate, n-propanol, propylene glycol methyl ether and anhydrous ethanol. Specific ratios can be adjusted for different ink systems.

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

Implementation of the solvent residue limit will rapidly drive fully alcohol-soluble inks and water-based inks forward. Today's cigarette pack inks are mainly solvent-based NC systems. Even with strict specification control and process adjustments, they can meet VOC limits, but their solvent residues are heavily affected by weather, printing environment and various press auxiliaries. That creates uncertainty and makes VOC control more difficult.

By contrast, fully alcohol-soluble and water-based inks offer clear advantages. Fully alcohol-soluble inks need only anhydrous ethanol as the dilution solvent during printing. Water-based inks require just a suitable amount of ethanol to adjust drying speed, with no other toxic or harmful organic solvents, greatly reducing the risk of VOC exceedance. Replacing existing solvent-based inks with these alternatives is therefore an inevitable trend.

To address VOC exceedances, our company has had many exchanges with printing customers and learned about the problems and solutions found by some printers during self-inspection. The summary below may serve as a useful reference for industry peers.

Case 1: A printing company used a GC-3061C gas chromatograph and found benzene exceedance. Yet after testing the ink, paper and diluent separately, no benzene solvent was detected.

Analysis: A wider investigation showed that a diluent supplier had supplied ethyl acetate in a drum that had previously contained benzene. The solvent in that drum had already been used up, while solvents in other drums did not show the same issue. After the printing company required the solvent supplier to use drums for delivery, benzene exceedance no longer occurred.

Solution: Strictly control reusable containers and dedicate each drum to one specific use.

Case 2: A printing company in Henan generally ran its press below 150 m/min and used large amounts of butyl acetate as a diluent in the ink. Testing with a GC-3061C gas chromatograph showed butyl acetate at about 17 times the limit, while propylene glycol methyl ether measured only 0.3, far below the required limit of 60.

Analysis: Butyl acetate evaporates slowly and tends to remain in the print. Its limit in the standard is 5, which is relatively strict. Slow-drying solvents with low limit values should therefore be avoided.

Solution: The customer switched to a diluent blend of ethyl acetate and propylene glycol methyl ether at an 8:2 ratio for printing. This maintained print quality and brought test results within the required limits.

Case 3: A printing company in Hubei used a gravure press at 230 m/min, with dryer temperatures set close to the high end at 110°C. Nevertheless, submitted samples still showed ethanol about twice the limit.

Analysis: Ethanol evaporates quickly in gravure solvent ink systems and is a fast-drying solvent, so large residues are not normally expected. The root cause was excessive dryer temperature in the printing units. Once the surface dried, solvent release from the inner layer was restricted, leading to exceedance of a fast-drying solvent.

Solution: The customer adjusted the press unit temperatures so that they increased in a gradient from the first to the last unit, and also increased air-blow force. This effectively resolved the ethanol exceedance.

Case 4: A printing company in Jiangsu used the solvent ratio recommended in Case 2 as its diluent. After printing, GC-3061C gas chromatography testing found propylene glycol methyl ether at about twice the limit.

Analysis: Propylene glycol methyl ether evaporates slowly. If its dosage is kept within 20% of the diluent, exceedance is generally unlikely. Testing the propylene glycol methyl ether used by this customer with a GC-3061C gas chromatograph showed purity of only about 75%.

Solution: The customer switched to a comparable product from a reputable manufacturer, and the test data met requirements. When using any solvent, always ask the supplier for a purity analysis report.

The GC-3061C gas chromatograph is a cost-effective analytical instrument. It uses microcomputer control, keyboard operation and an LCD screen with a Chinese menu interface.

It offers high electronic circuit integration, good reliability, simple operation and memory for set parameters, so settings do not need to be re-entered each time and long runs are supported. A large column oven and large fan, combined with an automatic rear-door cooling system, improve oven cooling speed and enable operation at room temperature plus 5°C. The large LCD Chinese display makes operation easier to learn, and automatic electronic ignition is included.

Other features include self-diagnosis, over-temperature power-off protection, file storage and recall, five-stage programmed temperature ramping, and single-column automatic compensation to keep the baseline stable during programmed temperature analysis.

The instrument has three injection ports for dual packed columns and capillary columns, along with independent three-gas pathways.

It provides six independently controlled temperature zones and an intelligent rear-door system for very fast cooling. Vaporization chambers, detectors and amplifiers use modular designs, making installation and replacement highly convenient.

A separate, complete capillary analysis system is included, with an independent capillary split injector covering septum purge, split and make-up adjustment. An optional capillary split/splitless injector is also available.

The instrument can be equipped with five detector types: flame ionization, thermal conductivity, flame photometric, electron capture and nitrogen-phosphorus. Up to three can be installed at once, and users can select according to their analytical needs. Options such as six-way valve injection and a converter furnace can be added, and detectors can operate in series or parallel.

—This article was reposted from China Packaging Network (pack.cn). Original link: http://news.pack.cn/show-362256.html