Flexo inks are water-based, solvent-based or radiation-cured ultraviolet (UV) or electron beam (EB). Since ink represents one of the most common and with the solvent-based inks, the largest hazardous waste stream, it makes inks a prime candidate for good management approaches. There are a variety of procedures that can be employed to minimize ink use resulting in less waste.
Best Management Practices & Pollution Prevention
To manage the use of inks:
Try to use inks with pigments containing little or no heavy metals such as lead, barium, cadmium, mercury, and chromium. These metals are regulated by federal waste disposal laws, local waste water discharge regulations and the Coalition of Northeastern Governors (CONEG) who have set strict levels for lead, chrome, mercury, and cadmium in inks used for packaging. Ink suppliers can manufacture most inks with alternative pigments that do not contain heavy metals. Check with the supplier and review material safety data sheets (MSDSs).
Other metals commonly found in ink pigments, such as copper and nickel, may be regulated by state or local wastewater discharge laws. Check with your supplier for inks that do not contain regulated metals.
Dedicate print stations (print decks) to specific colors or special inks to decrease cleaning requirements.
Regularly monitor pH and viscosity of water-based ink during a press run to reduce the time and amount of additives needed to optimize print quality.
Regularly monitor the viscosity of solvent-based inks during a press run to reduce the time and amount of solvent additive needed to optimize print.
No matter what type of ink is being used, printers can increase efficiency by printing a thinner ink film thickness. While this may require some changes, a thinner ink film allows for faster drying times and higher press speeds. To print a thinner film, printers may need to minimize the anilox roll cell volume, use ink that has a high pigment loading and install doctor blades. Adjustment of the ink drying speed will probably be necessary.
Films can be co-extruded to have panels of color in a clear field. This has been done for bread bags and garment bags. White panels are extruded into the clear film. Printing is accomplished without the need to lay down a heavy coverage of white ink prior to printing colored inks.
Methanol, a HAP material, was historically commonly used as a denaturant for ethyl alcohol. Many non-HAP materials can be substituted for it with no loss of quality or efficiency.
Methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), both HAPs, are used in very minute quantities as denaturants. These can be removed from ethanol blends without any loss of performance characteristics.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
Solvent is the primary pigment carrier in solvent based inks and aids in the drying process. The solvent in solvent based inks is considered a VOC (a.k.a. VOM). When the solvent evaporates due to ink drying either due to ambient exposure (can left open) or mechanical drying (press dryers) the VOC's are emitted. The emission of these VOC's is an air pollutant that is regulated by the state environmental regulatory and U.S. EPA. An air emission permit may be required by the state and/or U.S. EPA depending on the amount of VOC and hazardous air pollutant (HAP) that is emitted from the entire facility.
Subsequently records of the monthly emissions based on usage of VOC containing products must be maintained. If a permit is required, typically the permit will have specific record keeping and reporting conditions. These conditions may include the requirement to submit a summary report of the VOM and HAP emissions for the previous calendar year. Additionally, the printing facility is required to verify that they are in compliance with the permit limits based on record keeping requirements. If the facility exceeds the interim (i.e. monthly VOM emission limit), then the state or federal regulatory agency must be notified and appropriate follow-up reports filed.
Water is the primary pigment carrier in water based inks and ammonia compounds aid in the drying process. Most water based inks contain a very small portion of solvent that contributes to a small percent by volume of VOC content (typically less than 1% by volume). This small percentage can still add up to significant amount of VOC emissions, especially in high volume flexographic printing operations. The emission of these VOC's is an air pollutant that is regulated by the state environmental regulatory and U.S. EPA. An air emission permit may be required by the state and/or U.S. EPA depending on the amount of VOC that is emitted from the entire facility. As with solvent based ink, records of monthly emissions based on usage of VOC containing products must be maintained.
Radiation Cured Ink
Chemicals emitted through the curing of UV and EB inks are not regulated at this time. However, the solvents and cleaners used to clean up the equipment with does emit VOC's. See the equipment cleaning section of the chemicals.
RCRA Section 313
All ink has the potential to contain chemicals and metal compounds that are regulated under U.S. EPA's RCRA Section 313 regulations. Product manufacturers are required to list Section 313 reportable ingredients and the percent by volume in the product on the MSDS. The MSDS should be carefully to determine which products contain reportable materials. Appropriate calculations to determine the amount stored and consumed each calendar year must be maintained.
There are various reporting thresholds depending on the chemical or metal regulated by Section 313. The printer must be aware of the reporting limits and the amount stored and consumed at the facility to determine whether a report must be filed with the state environmental regulatory agency or U.S. EPA.
Ink waste may be considered a hazardous waste if it exhibits a flashpoint of 140 degrees Fahrenheit or less or contains F-Listed solvents.
Water based ink waste may be prohibited from being discharged into the sewer even if it is not flammable or combustible. Many municipalities have restrictions on the amount of color the waste water can hold.
If the facility is discharging waste water into a septic system, then industrial waste water is strictly prohibited from discharge. All waste water generated as a result of production activities must be treated and discharged off site. Only sanitary water from sinks and toilets may be discharged into the septic system.
PNEAC Toxic Release Inventory Resources
Health & Safety
Most solvent based inks present a fire hazard, and it is important to take note of flash points and explosive limits. Use explosion-proof tools in ink rooms or press areas where flammable liquids are being used or stored. Never use electric extension cords in explosion proof areas where solvent or solvent based in is stored.
Use of proper protective equipment, such as safety glasses, gloves and an apron should be used when handling the ink and ink waste.
UV inks can be a skin irritant. Appropriate personal protective equipment including gloves and aprons should be worn when handling the ink.
The UV and EB curing equipment can cause skin and eye damage due to the high intensity UV light and the EB. Proper shielding should be in place at all times. When the equipment must be maintained, such as replacing bulbs, the printing press and curing unit should be locked out using the OSHA Lock Out/Tag Out procedures to assure personnel safety.
See Health and Safety Sections for