MATERIALS | MINERAL FILLERS
Right: Greenspar products, sourced from Greenland, are available as a dust-free 95% filled master- batch in various resin systems
Celestial Materials, which toll-produces various types of masterbatches containing up to 95% filler loadings using a proprietary low-shear technology. “Another unique aspect of Greenspar is its availability as both a powder and as a 95% filled masterbatch in polyolefins, polyamides, PVC, and other polymers,” he says. “The masterbatch [intend- ed for use by compounding companies] will allow for handling and feeding of ultra-fine powders in a format that looks and feels like resin. They are designed for high throughput and high dispersion. They solve a critical need in the market to ensure a dust-free environment while maximising through- put and properties without the need for any powder handling systems.” Hanrahan views Greenspar as an alternative to other silicate minerals, most notably kaolin, but also as a replacement for wollastonite and mica, even though aspect ratios are sometimes different. He highlights its ability to reduce warpage in products, although points out it has little reinforcement effect. “I see glass/Greenspar hybrids as a great opportunity,” he says. Hanrahan says Greenspar requires less process- ing than alternatives (no calcination is required for example) and believes the company will be able to supply to compounders around the world — and certainly to those in the Northern Hemisphere — at competitive cost. “Our location is right on a deep-water fjord allowing for efficient transporta- tion to North America, Europe, and – especially when the Northwest Passage is open – Asia,” he says. The mineral will be shipped out of Greenland to milling and surface treatment operations in strategic locations. The company is currently in advanced planning for operations in the US and in Europe, with possible capacities of around 30,000 tonnes/yr. It already has a warehouse in the US. The company also claims that its Greenspar
products are very environmentally friendly. “Our deposit is high-purity, fully exposed at the surface,
Table 1: Key comparative data for calcite/limestone and oolitic aragonite mineral fillers
Test
Specific Gravity Mohs Hardness Crystal Structure Surface Area Zeta Potential Crystallinity
Microporosity
Calcite/Limestone 2.6 – 2.8 3
Trigonal 0.55 m2
/g
-1.01mV to 11.55mV Low Low
Source: Calcean Minerals & Materials 18 COMPOUNDING WORLD | June 2021
Oclitic Aragonite 2.8 – 3.0 3.5 – 4.0
Orthorhombic 1.82 m2
/g
-33.85mV to -6.65mV High
Very High
and contains no entrained water. This means our products are made without extensive stripping or thermal processing and require no wet processing to purify.”
Marine opportunity In contrast, calcium carbonate could be considered to be at the other end of the supply spectrum; it has been used in plastics for decades and is mined all around the world. Even so, new sources are becoming available, some of them with interesting USPs. Calcean Minerals & Materials, which is headquartered in Gadsden, Alabama, claims to offer a renewable calcium carbonate. CEO Anthony Myers says the company has developed unique processes to create high-performance products that can be applied in plastics as both a ‘green’ economic filler and a product enhancer. It has branded the materials as BioCal and OceanCal. Calcean is taking advantage of the vast under-
water deposits of aragonite sand – oolitic aragonite – found on the Great Bahamas Bank, which is located around 80 km from the US mainland. First investigated in the 1950s, oolitic aragonite was found to have unique physical and chemical properties that proved attractive as a raw material in many industries, from agriculture to construction materials (oolitic means egg-shaped). Oolitic aragonite is a biogenic product, which
means it is produced by living micro-organisms, and deposits are being constantly replenished. It forms naturally during seasonal bi-annual events called ‘whitings.’ During these, blooms of phyto- plankton move over the shallow banks of The Baha- mas, pulling carbon dioxide from the atmosphere and binding it to calcium in the water to ultimately precipitate out oolitic aragonite. Reserves on the Bahamas banks are estimated
www.compoundingworld.com
IMAGE: HUDSON GREENLAND
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