By Jan H. Schut
New biopolymer formulations are in the works for durables with very high biocontents of 90% to 100% for the first time, designed to compete head on with ABS for electronics, appliances, and auto parts. Several formulations use a new biopolymer that isn’t fully commercial yet, polybutylene succinate (PBS), which has properties like PP, but is biodegradable into CO2 and water. PBS itself isn’t new. Showa Denko KK in Tokyo (www.sdk.co.jp), launched the first commercial PBS, “Bionolle,” in 1993 as a niche polymer for biodegradable applications like fishnets and for automotive applications.
Whether petro- or bio-based, PBS is made from roughly 60% succinic acid and 40% butane diol. Showa Denko began to offer bio content PBS in 2012, with bio succinic acid from Myriant Corp., Quincy, MA (www.myriant.com), through a semi-works plant in Lake Providence, LA, but Showa Denko’s PBS capacity is reportedly less than 12 million lb/yr and not dedicated.
In August 2015, PTTMCC Biochem Co. Ltd., in Rayong, Thailand, started up the world’s first dedicated biocontent PBS plant and is sampling customers. PTTMCC uses bio succinic acid made by BioAmber Inc.’s new monomer plant in Sarnia, Ontario, which also started in August, using patent-applied for technology (U.S. Pat. Applic. # 20140242652) from Mitsubishi Chemical Corp., Tokyo (www.mitsubishichem-hd.co.jp). For now the BDO is petro-based, so the PBS won’t have more than 60% biocontent. PTTMCC’s capacity is 40 million lb/yr, still only a semi-works size, so there won’t be a lot of biocontent PBS available even in full production. PTTMCC is a joint venture between Mitsubishi Chemical, and PTT PLC Ltd. in Bangkok, Thailand. A sister company of PTT owns Myriant and also owns 50% of NatureWorks LLC, Minnetonka, MN (www.natureworksllc.com), maker of Ingeo PLA, the world’s largest volume biopolymer.
Bio PBS targets mulch films and packaging for biodegradability. But so far no PBS has claimed a “letter of no objection” for food contact from the U.S. Food and Drug Administration. Meantime the most interesting PBS technology to appear is high-biocontent compounds developed by automotive tier one supplier Faurecia SA, Nanterre, France (www.faurecia.com). Though Showa Denko and Mitsubishi Chemical have offered petro PBS for auto parts for years, what makes Faurecia’s PBS unusual is that it will be 100% bio.
Faurecia started an ambitious 15-year development program in 2006, more than 10 years before bio PBS was available, and planned in three material stages. The first material, a patent-applied-for composite (U.S. Patent Applic. # 20140291894), called NafiLean, took five years to commercialize, and is composed of 20% short chopped hemp fibers and 80% PP. It’s used for non-visible door panel inserts and the “top roll” on Peugeot 308 cars, starting with model year 2013, and for an entire instrument panel on the 2015 Alfa Romeo Giullia sedan.
According to the patent application, the PP/natural fiber composite uses very high flow ethylene as a flow enhancer. Chopped hemp fibers were developed in a joint venture called Automotive Performance Materials in Fontaine-les-Dijon, France (www.apm-planet.com), between Faurecia and Interval Group, Arc les Gray, France (www.interval.coop), a large agricultural cooperative. The length and aspect ratio of the fibers is similar to short glass fibers, Faurecia says. Hemp fiber adds strength and makes parts 20% to 25% lighter weight than 20% mineral filled PP. Mineral fillers are not used in NafiLean.
Short hemp fibers are loaded at 20%-40% depending on applications. Interior car parts under glass need to withstand temperatures over 120 C, Faurecia’s patent application notes. NafiLean PF2 555 with 20% hemp fiber has an HDT at 264 psi (ISO 75/A) of 72 °C and an HDT at 66 psi (ISO 75/B) of 137 °C. NafiLean also shows “40% improvement in fit and finish” vs. mineral filled PP.
Faurecia’s second stage material is hemp-filled PBS, called BioMat, which is commercial this year. Faurecia and Mitsubishi Chemical signed an R&D agreement in 2012 to optimize PBS for car parts, preventing its inherent biodegradability, increasing HDT, and reducing its high viscosity for faster molding cycles. Faurecia invented a bio-based flow enhancer and bio-based heat stabilizer for a bio-based PBS copolymer with the necessary performance. The patent-applied-for flow enhancer (U.S. Patent Applic. # 20140088269) is described as an aliphatic biopolyester based on PBS plus a terminal epoxide group. This novel oligomer not only increases flow properties of PBS, but prevents aging degradation.
Fauretia’s patent-applied-for booster (U.S. Pat. Applic. # 20140005351) for HDT involves polymerizing a bio-based high temperature polyester, polyetheramide (PEA), starting from the same monomers as PBS–succinic acid and 1,4 butenediol–plus 1,4 butenediamine. This bio-based PEA can then be reactively compounded with PBS to make a PEA/PBS copolymer with higher HDT. Faurecia developed both the flow enhancer and PEA for automotive applications working with the Institut National de la Recherche Agronomique headquartered in Paris (www.inra.fr) and with Agro-Industry Recherche & Development in Pomacle, France (www.a-r.d.fr). Modifications of both technologies could potentially be developed for non-automotive applications.
Mitsubishi Chemical uses Faurecia’s technology and “specific protocol” to produce a high molecular weight “Bio PBS14” for Faurecia at PTTMCC’s new plant in Thailand. Faurecia then compounds roughly 70% bio-based BioMat including hemp fiber. BioMat passed an impressive series of auto industry tests including ultrasonic welding, noise damping, odor and VOC (it smells slightly of caramel) plus stringent German automakers’ dimensional specifications. Audi and Mercedes-Benz require dimensional stability and covering adhesion after 50 cycles from -35 °C to 80 °C with 80% relative humidity; four days (96 hours) from -30 °C to 90 °C with 95% relative humidity; and 30 days from -30 °C to 90 °C with 92% relative humidity.
In stage three, when bio-BDO monomer is commercially available, all-bio PBS will become available. Then BioMat will be 100% bio-based as well. It will culminate an extraordinary R&D effort by a processor to a new material.
OTHER NEW HIGH-BIO POLYMERS FOR DURABLES
NatureWorks’s Ingeo PLA, originally used mostly for packaging, has also developed two new high-biocontent injection molding grades for durables like appliances and electronics. One is medium impact, one high impact. Both use nucleating agents for rapid crystallization and higher HDT. The medium impact grade has 89% bio content with 11% modifiers and nucleating agents and HDT of 92 degrees C at 66 psi. The high impact grade has 88% bio content with 12% modifiers and nucleating agents, and HDT of 77 degrees C at 66 psi. Both are available in test quantities.
Wacker Chemie AG, Munich, Germany (www.wacker.com), also recently published data on blends of 40% PBS from Mitsubishi Chemical and 30% PLA Ingeo 4043D from NatureWorks, using 20% of Wacker’s Vinnex PVA-based compatibilizers to enhance properties, and 10% filler, either talc or calcium carbonate for a total of 70% bio content. The Vinnex part is comprised of 14% Vinnex 2504, a vinyl acetate ethylene copolymer for higher elongation and 6% Vinnex 2510, a vinyl acetate homopolymer for higher stiffness. Developmental PBS was supplied by Mitsubishi Chemical from a pilot plant. Ingeo PLA was supplied by NatureWorks.
Wacker claims higher impact and melt strength for the PBS/PLA blend, more flexibility, and higher heat resistance for appliances–about 100 °C vs. 60 °C for typical PLA. Vinnex also allows PLA and PBS to be combined in any ratio. Without compatibilizing, only 10%-20% PBS would be miscible with PLA. Wacker introduced Vinnex five years ago in the U.S. and six years ago in Europe and offers nearly a dozen grades. Wacker also has a patent application (WO2010133560) on biopolymer blends with flour as a filler, as opposed to refined starch, noting that unrefined flour brings gluten and fibers to strengthen biopolymer blends without adding sensitivity to moisture like refined starch.
NatureWorks previously offered two PLA/PBS blends with over 50% PBS, AW300D for injection molding and AW240D for thermoforming food service, in a joint venture with Montreal-based BioAmber (www.bio-amber.com) called AmberWorks. AmberWorks used technology BioAmber acquired in 2010 when it bought Sinoven Biopolymers Inc. in Philadelphia, PA, and China. But AmberWorks grades target packaging and aren’t actively sold.
Properties of High-Bio-Content Polymers for Injection Molding vs. ABS
|Ingeo PLA||20% hemp/PP||25% hemp/PBS|
|Medium Imp.||High Imp.||NafiLean||BioMat|
|Grade||“884-41-1”||“884-41-2”||PF 2555||NBF2 112||ABS|
|Specific gravity, g/cm3||1.22||1.21||0.98||–||1.04|
|Tensile modulus, kpsi||414||414||384||384||336|
|Tensile strength @ yield, psi||5400||5500||–||–||5600|
|Tensile elong. @ break, %||32||21||–||–||5.5|
|Notched Izod imp., J/m
(ASTM D256 method)
|Notched Izod imp., kJ/m2
(@23 °C, ISO 180 method)
|Flexural strength, kpsi||9.5||9.4||–||–||9.9|
|Flexural modulus, kpsi||455||448||–||–||345|
|HDT, @66 psi, °C||92||77||137||104||87|
|MFR 190 °C/5 kg, g/10 min||–||–||11.6||–||–|