Moulded pulp sounds like an uncommon name, but there’s a good chance that every household contains an item or two made out of it. But what exactly is moulded pulp? Molded pulp is a packaging material that is usually made from recycled paperboard and/or newsprint. You may have heard it as molded pulp or even molded fiber. Some everyday products that are made from moulded pulp would include:
- Egg cartons
- Phone books
- Clamshell containers
- End caps
- Fast food drink carriers
How Moulded Pulp Containers are Made
Step 1. The first step of the process involves making filler flats. Filler flats are the tray-like products that farmers use to ship out their eggs. The raw materials go into a pulper, which is like a gigantic blender that mashes and heats everything up at about 150°F. The hot water then causes the fiber material to swell and break apart. After about twenty minutes, the pulp has formed into an oatmeal-like water mixture and falls out the bottom of the pulper while being screened one last time for plastics and other impurities.
Step 2. Next, shaping the flats is a fully automated process. Formation molds descend into a tank filled with pulp and are sucked onto the vat belt by a giant vacuum. The formation molds go through a filter containing water jets on the way down that spray off excess dirt and unwanted substances.
Step 3. Transfer molds grab the flats off of the formation molds and move them onto another conveyor belt. They are grabbed pretty simply by quickly brushing them with a water-based lubricant. The molds are then covered with a stainless steel mesh, which ensures an even vacuum throughout the mold so that the pulp can be easily spread over it.
Step 4. The flats now go into a 400°F oven where they dry out for about 15 minutes to make them less soggy. This bonds the fibers together to form a more substantial material. Finally, a vice lifts up the molds so that they can stack into each other. The machine sections of the appropriate number of flats per package and are compressed and sealed into a plastic film to keep the dust-out.[Factories use the exact same process when making 4-cup drink carriers. The pulp only needs to dry in the oven for about half of the time of the pulp for filler flats because drink carriers are smaller and lighter weight.
Factories also make disposable urinal bottles for hospitals by adding chemicals to make them liquid tight. Since these products are 3-dimensional, they are lined with mesh inside. These bottles, however, take double the time cook and dry because of their requirement to be liquid-tight.]