NORWALK, CALIF. — Thermoplastics compounder Heritage Plastics Inc. has long believed in the processing and environmental benefits of using calcium carbonate as a filler in high density polyethylene film. Now, it says, it has the hard data to prove it.
The characteristics of calcium carbonate – the main mineral found in limestone, marble and chalk — allow polymers to heat and cool faster, resulting in significant energy savings through improved productivity, higher outputs and faster film conversion. Now, Heritage says, independent research confirms that use of the filler in HDPE film reduces petrochemical and energy usage during the manufacturing process, and minimizes the carbon footprint and greenhouse gas impact of finished plastic products.
Frank Ruiz, vice president of research and development of the Picayune, Miss.-based Heritage, revealed the results of life-cycle assessment tests of its HM10-brand calcium carbonate concentrate at a June 18 evening meeting of the Western Plastics Association in the Los Angeles suburb of Norwalk. Ruiz, a 27-year veteran of Heritage, said his firm contracted with Boustead Consulting & Associates LLC to conduct the LCA tests over the past three years.
The study analyzed the energy consumption and environmental impacts of using 100 percent pure polyethylene resin compared to displacing 20 percent of the PE resin with its HM10 additive, in both pre-film plastic pellet production and in film production scenarios. Boustead based its calculations on a database built over 25 years, and the LCA considered both the manufacturing process of Heritage's additive and its use in HDPE film production.
Some of the test findings, assuming the displacement of about 20 percent of the petrochemical-based components in film with the HM10 additive:
- 15-20 percent overall energy savings
- 16-20 percent reductions in the use of crude oil
- 15-19 percent reductions in the use of natural gas
- 12-17 percent reductions in the use of coal
- 12-16 percent reductions in the use of electricity
- 13-17 percent reductions of greenhouse gases
- 15-20 percent reductions of oxides of sulfur
- 13-17 percent reductions of oxides of nitrogen
- 11-15 percent reductions of particulates
Heritage said that producing one ton of its HM10 concentrate uses 72 percent less energy than producing one ton of HDPE. It further claims that replacing 20 percent of the HDPE in film with the additive reduces the amount of electrical energy needed to convert the film by 23 percent.
As such, the use of the additive can significantly reduce the end product's carbon footprint — an increasingly important consideration for some major customers and retailers such as Wal-Mart Stores Inc. that aggressively apply sustainability scorecards to their sourcing and purchasing processes.
And this benefit can be especially important to California film processors given that California Assembly Bill 32 dictates that any company that emits more than 25,000 tons per year of greenhouse gasses will be required to pay to participate in the state's cap-and-trade program. The allowable limits are due to become even stricter in 2015.
Still, there are side effects to consider. The introduction of calcium carbonate does negatively impact the optics of the film, acknowledged Ruiz. It makes the film appear “milky,” which rules it out for high-clarity applications, but which is not important for other applications.
Recyclers also have a concern, at least when it comes to the reprocessing of bottles and rigid containers made with a calcium carbonate filler. The high density of additive means that bottles made with it will be heavier than those made with the usual additive alternatives. This could complicate the float process that recyclers use to separate scrap HDPE flakes from other ground-up scrap resins such as PET. Ruiz said that Heritage currently believes that a 7 percent loading of calcium carbonate (to include any existing pigments or other additives) into the resin is the limit to keep the end product's density below the vital 1 percent level, which would avoid the problem feared by recyclers.
This is more of an issue for bottles than for film, which was the focus of the LCA study. Clean film scrap usually is recycled using a dry process, Ruiz said, which makes the density a moot point. The issue comes when the film is dirty and needs to be washed or when the HDPE is mixed with other types of resin scrap and needs to be separated.
He said Heritage has been working for the past three years with the Association of Post-Consumer Recyclers and the recycling community to ensure there is no contamination of the recycling stream.
Calcium carbonate concentrates can be found in a variety of applications, Heritage notes, including injection molding, blow molding, sheet extrusion, thermoforming and extrusion coating, but this LCA research focused on the HDPE used to make film and bags, which accounts for about half the PE market. Roughly 1 billion pounds of HDPE is converted into bags a year, Ruiz said. Still, he noted, Heritage has seen similar benefits of using HM10 in low-density PE resin, and in cast film as well as blown film.
Heritage produces the HM10 concentrate at its Sylacaugua, Ala., plant, which is near one of the world's largest limestone mines.
Ruiz, who lives in the Dallas area, began his career as chemical engineer with Union Carbide Corp., and worked a year for Monsanto before joining Heritage in 1986. In recent years, he also served concurrently as president of Carrollton, Texas-based Plastimin LLC, a supplier of polymer concentrates and bioplastic-based compounds.
Plastimin opened its doors in 2005 as a minority enterprise that was majority owned by Ruiz, who is of Puerto Rican descent. But Plastimin, which was primarily a distributor, shut down in 2011, Ruiz said, when the accounting rules governing minority enterprises changed and eliminated most of the benefits associated with such arrangements.
