Macro Engineering and Technology Inc. has developed and patented a new method to produce trash bags and similar film products from post-consumer material.
Nowadays, when producing bags containing high amounts of reclaim, most processors “bury” the scrap in the core layer of a multi-layer structure, and sandwich it with skin layers made primarily of virgin material. The problem with that method is that impurities originating from the scrap layer—such as gels and pins holes—tend to migrate or “leak” through all the layers of the structure, explains Mirek Planeta, the former president of the machine builder who now heads up the firm’s R&D efforts. "In two- or three-layer coextrusion, when (the material exits) the die all of the layers are aligned, so any impurity will create a fault or defect in all the layers at the same time," Planeta explains.
Macro patented approach is to produce the bag from two separate films, which are blocked after they the exit die to prevent any gels or pin holes from aligning. This arrangement adds to the film strength because one film with the defect is essentially "covered" by the second film without the defect. The film is blocked so that the two layers act as one to prevent the gel or other defect from seeping through, Planeta notes.
This can be achieved by blocking a two-layer tube, or by extruding using a dual-orifice die to create two bubbles, thereby producing two separate films. It can be done with one or more extruders.
In trials at its plant in Mississauga, Ontario, Macro found film produced by this method showed an improvement in both tear strength and tensile strength. Macro trialed both blends of post-consumer scrap with virgin, as well as a structure in which both of the bubbles were made of 100% reclaimed consumer scrap structure (photo). Both cases showed no evidence or gel leakage or pin holes, Macro officials state.
The company's intention is to license the technology to interested processors.