Plunger Solvent Dispenser Reduces Emissions and Solvent Use
The largest amount of solvent or related chemicals used normally occurs during clean-up of the print stations.
When blanket and impression rollers are cleaned manually, not only is more water/solvent used, but also hand cleaning using shop towels is required. These towels must be sent out for cleaning or be disposed of. Automated blanket washers can increase press utilization rates by 25 percent and reduce blanket wash consumption, which then reduces the volume of hazardous waste solvent being generated. It also reduces the number of soiled shop towels being disposed of or laundered. This allows more product to be printed in the same time period.
Best Management Practices & Pollution Prevention
Automated Roll Cleaning with Alkaline Cleaner
Alternative, less hazardous, cleaning products are available and work well. For example, many low or no VOC products that are lactate based (soy and corn derivatives) work well to cut ink. Additionally, caustic cleaners (high pH) may be a good alternative to high VOC emitting products.
Particle blast cleaning systems that emit no VOC's, using plastic beads or fine particles such as CO2 or baking soda are useful for cleaning press parts.
For enclosed doctor blade chambers, less solvent can be used to wash down the ink fountains and rolls. Only the chamber must be hand wiped, but this part is much smaller than the ink pan and requires very little solvent to be completely cleaned. Only the anilox roll needs to be cleaned on-press. The remaining parts, including the chamber system can be placed in an appropriate washtub. It is a more efficient cleaning system and uses considerably less cleaning solvents or caustic water solutions. This results in a reduction of hazardous waste from cleaning operations and reduced emissions from cleaning solvents. For the press operator, this also allows for faster and less difficult cleanings between print jobs.
Some doctor blade systems are automated for wash-up while the doctor blade remains in the printing position. Automated cleaning systems can further reduce waste in several ways. Most systems utilize a first stage recirculation wash mode where used dirty water/solvent is used to do the initial cleaning. This dirty water/solvent is returned to a common tank after each wash and can be reused many times. If done properly, this first stage wash actually can do most of the cleaning. Clean water/solvent is used for a final rinse only.
It is almost impossible to manage these waste streams manually; so wash ups are typically done with clean water or a reclaimed solvent, all of which goes into waste. When chambers and anilox rolls are cleaned manually, not only is more water/solvent used, but hand cleaning using shop towels is required. These towels must be sent out for cleaning or disposed. Automated cleaning chambers can increase press utilization rates by 25 percent. This allows more product to be printed in the same time period.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
The towels used for manual cleaning must be sent out for cleaning or disposed according to state and federal shop towel management requirements. Disposable shop towels may be considered a hazardous waste if they contain solvents.
VOC's and HAP's may be emitted from the cleaning products being used. Which must be considered when evaluating air permitting issues. In addition, some of the solvents may be classified as Section 313 (TRI) reportable. Records must be maintained to determine if reportable quantities are used or stored within the calendar year.
If using water based inks, water containing ink and cleaning compounds are generated during the process of cleaning press. The wastewater may be restricted from discharging into the sanitary sewer depending on the type of inks and cleaning products used. Depending on the pigments in the waste, which may contain regulated metals, the waste may be classified as hazardous. The regulated metals differ among each state.
If using solvent, UV or EB curable inks wastes containing ink and cleaning solvent are generated during the process of cleaning the ink metering system's parts. The waste may be considered a hazardous waste due to flash point, F-listed solvents, or pigments, which may contain regulated metals. The regulated metals differ among each state.
Health & Safety
Formaldehyde and vinyl acetate are hazardous materials and, if possible, should be eliminated from the adhesive formulation. If the formaldehyde and vinyl acetate cannot be eliminated from the glue formulation, employees should be monitored for exposure to excessive levels of formaldehyde and vinyl acetate, especially since these materials can lead to long term health affects.