The original flexographic printing plate was composed of rubber. There are several steps to make molded rubber flexographic printing plates. A master pattern (or engraving) is made by exposure through a photographic negative. A photographic negative is imaged and developed by using traditional black and white silver halide film and chemistry (i.e., developer, fixer, and wash water).
The master is typically made from magnesium, but can be a hard durometer photopolymer plate with a steel backing. The master pattern is used to make a phenolic (or matrix) mold. The mold is comprised of either phenolic powder or layers of paper with a phenolic coating. Finally, the molded rubber plate is made under pressure and temperature using the phenolic mold as a template. During this process, the rubber plate is cured. Rubber plates can also be engraved with a laser in lieu of a physical process. A laser engraved rubber plate is completely imaged electronically with no need for film and its processing chemistry. A laser literally burns away the plate material at predetermined depth creating the relief.
Best Management Practices & Pollution Prevention
Generated from washing a metal master for molded plates. Must be handled properly. Waste acid can be neutralized with alkaline chemicals and then discharged into the sanitary sewer (not permitted in Septic System. Simple neutralization is permitted by EPA RCRA regulations without being considere on-site hazardous waste treatment.
From processing a photopolymer master. If heated tap water is used, everything from the wash-out can be put down the drain if sewer system and local ordinances will allow.
May be sent to metal dealers for recycling.
Can be landfilled.
Phenolic (matrix) Molds
Are non-hazardous materials and can be landfilled, along with any scrap mold material.
From laser engraved molded rubber plates. If the facility has pollution control device (PCD), then the residue should be exhausted from the engraver as the rubber is being engraved, into a PCD (i.e. oxidizer). The residue is then burned within the PCD and the resultant emissions are water vapor and carbon dioxide. If no pollution control device is provided the engraving residue must be exhausted outside and then counted toward particulate emissions.
Compounds have to be cleaned with solvents, thereby creating hazardous waste, which must be disposed of properly. When using solvents, the cleaning procedure requires adequate ventilation and the proper personal protective equipment.
Can be pieced together minimizing waste. Cured scrap rubber, or flash, as well as the cured plate, is non-hazardous material and can be landfilled. Rubber plates - Can be recycled the same way as worn out tires, but at this point it is not economically feasible.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
Generated from washing a metal master for molded plates. Must be handled and disposed of properly.
Generated from rubber plate making activities must be handled as a combustible and/or hazardous waste according to the waste’s particular waste characteristics.
If the facility discharges waste water to a septic system, then no industrial waste waters may be discharged. The plate making waste water must be transported off site for treatment and disposal.
Health & Safety
Acid solutions should be handled with care. Gloves, goggles, and aprons should be provided to employees and instructed to wear when working with plates and the acid solution.
Solvent solutions, which may be flammable or combustible, should be handled with care and properly stored in fire safety cabinets/containers.