Conference Report: Bioplastics Are Breaking Out of Their 'Green' Niche
Close Up: Biopolymers
The excitement in the air of the recent Innovation Takes Root conference was a sense of arrival. The feeling among the 329 attendees from 171 companies and 21 countries was that bioplastics are starting to graduate from the “emerging technology” stage to market acceptance as everyday materials. This third “ITR” conference, sponsored by NatureWorks LLC, Minnetonka, Minn., the maker of Ingeo PLA bioplastics, presented 50 speakers and 32 exhibitors from materials, additives, and machinery vendors, processors, academia, food processing, and other sectors. They presented a growing volume and variety of applications from disposable packaging to durable goods as confirmation that bioplastics are not a mere fad, a “green” public relations stunt, or a feel-good eco-luxury, but legitimate tools of industry.
That point was summed up in an address by NatureWorks CEO Dr. Marc Verbruggen. He summed up the change in market attitude: In the 1990s it was, “Bioplastics are for biodegrading.” In the 2000s it was, “Bioplastics sequester carbon.” In the 2010s it will be, “Bioplastics are plastics.” He said that bioplastics today have three value propositions: Environmental benefits (sustainability) are just one of them. Another is relative price stability in comparison with petrochemical-based plastics—and possibly even lower cost. In addition, national governments are recognizing the merits of anything that reduces dependence on imported oil and gas.
DEMOLISHING THE THREE ‘MYTHS’
Verbruggen expanded his argument by addressing three pervasive, outdated “myths” about bioplastics:
Myth # 1: Bioplastics are intrinsically more expensive than conventional plastics. Verbruggen said that by 2015, when NatureWorks expects to have two commercial plants (in Blair, Neb., and Thailand) with a total capacity of 700 million lb/yr, using three feedstock sources (corn, sugarcane, and cassava), his target is that Ingeo PLA will be “structurally less expensive than PS and PET. He said this target is in view already, at least on occasion.
For example, he noted that in the fourth quarter of 2011, Ingeo PLA cost 90¢/lb in bulk, vs. $1/lb for PS and 80¢ for PET. The next big battle, he said, is to make PLA end products more cost-competitive, which will require economies of scale in processing—meaning more extrusion, thermoforming, and molding lines dedicated to PLA products.
Myth #2: Bioplastics will affect food availability and prices. According to Verbruggen, if there were enough PLA capacity to replace all 4.6 billion lb of PS consumption in North America, it would consume only 1.65% of today’s sugar production. But even that’s misleading, he pointed out, because within three to five years, the bioplastics industry will have access to fermentable sugars from cellulosic biomass—agricultural waste such as corn stover or wheat and rice straw, as well as nonfood crops such as switch grass (see sidebar below).
Myth #3: There are no recovery/recycle options for bioplastics. To date, most PLA recycling has been reuse of post-industrial scrap , but Verbruggen said automated sortation of post-consumer PLA from other plastics, using NIR (near infrared) sensors, has been demonstrated in Italy and elsewhere. Other PLA users are investigating recycle programs . A growing roster of bioplastic compounders is eagerly looking for recycle, as is NatureWorks, which already uses its own post-industrial scrap in chemical recycling—breaking it back down to lactic acid monomer and then repolymerizing it into virgin PLA.
As compared with recycling, “Composting a plastic in isolation makes little sense,” stated Verbruggen, because there’s no energy recovery and no carbon storage. On the other hand, he noted, “Use of compostable items to divert organics from landfills makes a lot of sense.” So, for example, bioplastic fast-food-serviceware and compostable bags for food or yard waste have a place.
There is already a firm dedicated to PLA recycling. BioCor LLC, Concord, Calif. (biocor.org), buys PLA from processors and assists in separating PLA scrap from other materials. BioCor then sells the PLA to mechanical reprocessors or PLA resin manufacturers.
One processor that just started a pilot project in PLA recycling is yogurt maker Stonyfield Farm, Londonderry, N.H. It began working with NatureWorks on mechanical recycling of Ingeo trim scrap from its thermoform/fill/seal packaging lines. The initial goal is to find other users for the material in nonfood applications. In future, the hope is to develop a closed loop to chemical recycling of the PLA by NatureWorks (natureworksllc.com).
Stonyfield is also a case in point about the changing economics of biopolymers (see Myth #1). The company packages its yogurt in Ingeo cups formed from sheet supplied by Clear Lam Packaging Inc., Elk Grove Village, Ill. Until it converted to modified PLA in 2010, Stonyfield used PS sheet 35-mils thick. Its PLA sheet was initially 30 mils, which was downgauged to 28 mils last fall.
Now, Stonyfield and Clear Lam are reducing thickness even further to 26 mils. This was made possible because PLA outperforms PS: It is stronger, with less breakage; has better lid adhesion; and allows lower temperature processing, reducing energy use. All this was accomplished with no change in line speed or product shelf life. Thanks to this downgauging (and the rising price of PS), Stonyfield officials see no cost penalty in having converted to biopolymer.
Apart from inspiration and context, the conference and exhibits presented a lot of technical and market news.
NEW INGEO BIOPOLYMER ALLOYS
As reported last month (see March Starting Up), NatureWorks launched a joint venture with BioAmber, a biobased chemical company in Minneapolis with a development-scale production plant in France. The 50:50 venture, called AmberWorks, will produce blends of PLA and succinic-acid based biopolymers, such as PBS (polybutylene succinate) and PBSA (PBS-adipate copolymer). BioAmber is already producing biobased succinic acid, which has been sampled to several existing PBS producers that could be sources for AmberWorks (Plymouth, Minn.) to provide PLA blends via compounding partnerships. AmberWorks will use special know-how developed by a French firm, Sinoven Biopolymers Inc., that was acquired by BioAmber in 2010. The resin blends will be marketed exclusively by NatureWorks under its Ingeo tradename.
While pure PLA is stiff and brittle like PS, pure PBS is more flexible than PE. The new blends, therefore, exceed PLA in flexibility, toughness, and heat resistance—resembling PP, HIPS, or PVC. Two developmental thermoforming and injection grades are already available (see accompanying table for properties).
The injection molding grade (Ingeo AW 300D) is aimed at tableware used with hot foods and drinks. The sheet extrusion/thermoforming grade (Ingeo AW 240D) is for foodservice ware such as hot and cold drink cup lids, vending cups, trays, plates, and bowls. Both are opaque, off-white materials. Both are said to meet FDA requirements for food contact under the so-called “housewares exemption.” These blends are biodegradable and are expected to meet industrial composting standards (tests are under way). Planned future grades will offer enhanced heat and impact resistance, processability, and compostability.
Like Ingeo PLA, the new blends will eventually be 100% bio-based. BioAmber produces bio-succinic acid (a food additive and flavoring ingredient) by a fermentation process from wheat at its 3000-metric-ton/yr French plant. The company will later use technology licensed from DuPont to make the other feedstock for PBS, butanediol (BDO), from the succinic acid.
For the present, however, the BDO portion of AmberWorks’ PBS is not biobased. BioAmber plans to build its first full-scale production plant in Sarnia, Ont. When it opens next year, it initially will have 17,000-m.t. capacity for bio-succinic acid (fermented from corn). At full capacity, the plant will produce up to 34,000 m.t. of bio-succinic acid and 23,000 m.t. of bio-BDO. The plant will be built jointly with Mitsui & Co. The two firms plan two additional facilities in Thailand and either Brazil or the U.S.
NatureWorks sources note that PBS is produced from petrochemicals by other firms, such as Mitsubishi Plastics and Showa Denko in Japan. Its acceptance, however, has been limited by high prices. NatureWorks is introducing its bio-PBS blends at $2.00 to $2.50/lb, a price that is expected to drop as production expands. It should also be noted that FKuR of Germany (fkur.com, U.S. office in Cedar Park, Tex.) already sells PLA/PBS blends in its Bio-Flex series, though the PBS is derived from petrochemical sources. The company is testing bio-PBS, however, and plans to use it commercially by 2013.
Incidentally, the German plastics and chemicals company Lanxess (U.S. office in Pittsburgh) purchased a $10-million minority stake in BioAmber and a seat on its board of directors just 10 days after the NatureWorks joint venture was announced.
And PTT Global Chemical of Thailand, half-owner of NatureWorks (the other 50% is owned by Cargill, Inc.), formed a joint venture with Mitsubishi Chemical last year, PTT MCC Biochem, to develop a second source of biobased PBS.
MORE NEW BIOMATERIALS
One of the hottest areas of development is in durable or semidurable goods made from blends of conventional and renewable polymers. Dr. Robert Barsotti, research scientist at the Altuglas International unit of Arkema Inc., Philadelphia (plexiglas.com), presented the new family of Plexiglas Rnew alloys of acrylic and PLA for consumer, optical, automotive, and other markets. As reported last July (Starting Up section), what’s remarkable about these blends is that the renewable content adds more than sustainability value—it actually improves the processability and end-use performance of the conventional polymer.
Barsotti showed that adding 25% or more of PLA to PMMA adds a “drastic” increase in melt flow and a substantial increase in elongation and ductility to PMMA properties while increasing the heat resistance and weatherability relative to PLA alone. Heat resistance and scratch resistance are lower than for straight acrylic, and haze increases slightly as well, though optical transmission is unaffected. PLA and PMMA are fully miscible in all ratios, so blends can be easily tailored.
The next step is development of high-performance blends of acrylic and biopolymers. The higher flow provided by the renewable component allows use of a higher-molecular-weight acrylic component, which can achieve a “step change” in impact strength (comparable to PETG and PC) and significant increases in chemical resistance, exceeding that of some chemical-resistant acrylics and other clear resins. Toughness can be enhanced while using less rubber modifier, which allows increased stiffness. These newer blends are expected to arrive this year.
PolyOne, Cleveland (polyone.com), is also working to fill what it sees as an unmet need for biobased materials with properties suitable for durable applications. The company is developing its reSound family of blends of conventional engineering thermoplastics with a variety of biopolymers (minimum 30% renewable content). V.P. of scientific development Roger Avakian said PolyOne has customized formulations for specific customers to optimize, for example, low-temperature impact, HDT, UV or hydrolytic stability, electrostatic dissipation, fungal resistance, bio or recycle content, thermoformability, paintability, or overmolding adhesion.
At this conference, he focused on a current development program aimed at a non-halogen flame-retardant reSound blend for electronic enclosures. Avakian said PolyOne has come up with a proprietary formulation of PLA and at least two other resins that closely matches the property profile of a benchmark material for this marke, Bayblend FR3010 PC/ABS from Bayer MaterialScience, Pittsburgh. Like the benchmark, the new reSound FR grade (now in test marketing) meets UL 94V-0 at 1.6 mm. Elongation and notched Izod impact are around 20% lower for the new blend, but still competitive in the target applications, and stiffness and HDT are equal to or better than the benchmark. Avakian also said reSound FR has better properties and higher bio content than competing bio-blends.
End users are making strides on their own in developing bioplastics for durables. A leading example is the Innovation Research Laboratories of Japan’s NEC Corp. (nec.co.jp). It has worked with Japanese material suppliers to develop applications like a cell-phone housing of PLA/kenaf composite in 2006 and lighting made of that material in 2008. NEC’s Dr. Masatochi Iji said kenaf plant fiber increases PLA’s stiffness and heat resistance. Impact strength was improved by adjusting the fiber length and adding a biobased flexibilizer. In addition, moldability was enhanced with a nucleator to promote crystallization.
More recently, NEC worked with a materials supplier to develop nonhalogen flame-retardant PLA composites for PC and projector housings in 2010 and 2011, respectively. The compound includes alumina trihydrate, a phosphorus-based charring agent, and other additives. The compound is >75% biobased and achieves UL 94V-0 at 1.8 mm and V-1 at 1.2 mm. The compound is said to retain good flow and impact.
Dr. Iji reported on NEC’s newest developments, including PLA shape-memory compounds that utilize thermo-reversible crosslinking. If deformed and cooled, such materials resume their original form at 60 C (140 F). They can also be remelted and remolded.
NEC is also addressing heat-dissipation issues in ever-smaller electronic devices by developing thermally conductive PLA composites using crosslinked carbon fibers. Such compounds can match the heat conductivity of stainless steel at 10% carbon fiber loading and double the conductivity of stainless steel at 30% carbon fiber.
A third new NEC project is to increase the toughness of PLA with a nanoparticle filler. The company used silicone nanoparticles that were vulcanized and then blended into PLA. The particles have three layers—dense, rigid core; elastomeric middle layer; and outer layer with an affinity for PLA. These novel particles self-assemble from molecular units in solution. A 5% loading of this additive reportedly increases the elongation of PLA from around 2% to >6% while retaining its original flexural strength. Moldability and heat resistance are largely retained as well.
IBM Corp. also is pushing for biobased engineering blends for its large mainframe computers. Dr. Joe Kuczynski, sr. technical staff member in IBM’s Materials and Processes Engineering Laboratory in Rochester, Minn., said IBM launched a biomaterials initiative in Sept. 2010 to reduce the company’s environmental footprint. IBM uses 8-10 million lb/yr of plastics, 95% of that PC-based. So the company focused on PLA blends as an alternative to PC/ABS covers (Bayblend FR3010).
IBM forwarded its requirements to global compounders. It found the FR requirements to be the hardest to match with PLA blends. However, IBM is now qualifying a blend from a major compounder that contains PC and 30-40% PLA. This blend uses a new FR package that meets UL 94V-0 at 0.0625 in. IBM conducted molding trials at a custom molder on a computer cover with a tight grille pattern of ventilating holes.
The results were “excellent,” according to Kuczynski. The parts are now being evaluated for physical properties. Kuczynski believes IBM is three months away from commercializing this new material. Meanwhile, it is also evaluating blends with lower PLA content from other compounders.
Improving properties of biopolymers themselves is the goal of Interfacial Solutions, an materials-science R&D firm in River Falls, Wis. (interfacialsolutions.com). It has commercialized a family of deTerra products based on reactive twin-screw extrusion of PLA to induce “hyperbranching.” The result is >80% biobased and can have high flow for injection molding or high melt strength for extrusion. Impact strength can be enhanced from around 0.3 ft-lb/in. notched Izod for plain PLA to as much as 16.5 ft-lb/in. while retaining good stiffness and strength.
These products are alternatives to PVC, FR-nylon, PP, and ABS. (Also, deTerra expandable PLA bead is a substitute for EPS.) The first commercial grade is an extrusion resin for interior building profiles. This nonhalogen compound meets Class 1/A rating by the E-84 tunnel test, with zero flame spread and <70 smoke index.
Interfacial Solutions also is sampling a 94V-0 grade for injection molders. Future developments include work with other biopolymers such as PHA; improved heat resistance; and FR with higher impact.
Another R&D firm is SyntheZyme in Brooklyn, N.Y. (synthezyme.com). The firm genetically engineered a common yeast to ferment natural oils into ω–hydroxy fatty acids (ω-HOFA). The result can be used to make PUR polyols or can be polymerized by standard condensation methods to produce resins with PE-like structure and behavior. Properties include ultimate elongation >600%, stiffness between that of LDPE and HDPE, superior hydrolytic stability, rapid crystallization, excellent processability on standard molding and extrusion equipment, and full compostability. Additional potential is offered by reactive blending of ω-HOFA with PLA to produce flexible materials with elongation 50 to 100 times that of PLA alone.
Other interesting research is occurring at the Colorado School of Mines, Dept. for Chemical Engineering, Golden, Colo. Prof. John Dorgan, director of the Colorado Center for Biorefining and Biofuels, is developing nanocomposites of PLA and cellulose nanowhiskers to increase the thermal and mechanical properties of PLA while retaining transparency. His target is frozen-food packaging that can be hot-filled and microwave reheated.
Nanowhiskers can be obtained by acid hydrolysis of plant cellulose. Simple melt blending of PLA, whiskers, and impact modifiers produced a thermoformable material with enhanced HDT and impact. The next step, Dorgan said, is to functionalize the nanowhiskers by grafting PLA onto their surface. That turns the whiskers into highly effective nucleating agents, yielding higher HDT with low loadings in PLA.
Grafted alloys of PLA with enhanced properties are offered by Sukano Polymers Corp., Duncan, S.C. (sukano.com). Its Bioloy grades for injection molding boost impact and processing without need for drying. They are 100% biobased and fully compostable.
ADDITIVES & MODIFIERS
Among the firms exhibiting additives for biopolymers at the conference was HallStar Co. in Chicago (hallstar.com). Its Hallgreen line of bioplastics modifiers are liquid esters, fully or partially renewable, that are said to function as plasticizers and processing aids in starch resins, PLA, and other biopolyesters. Benefits include reducing melt viscosity and processing temperature and improving low-temperature flexibility and impact resistance.
Also exhibiting was Polyvel Inc., Hammonton, N.J. (polyvel.com), which offers a broad line of concentrates for PLA film, foam, and molding. They contain talc, silica, rubber, and other additives to enhance impact or melt strength; act as process aids, slip, release, or antiblock agents; or confer matte finish.
Sukano also provides a range of PLA masterbatches with slip, antiblock, mold release, processing aid, impact modifier, nucleant, UV stabilizer, optical brightener, or colors.
Segetis, Inc., Golden Valley, Minn. (segetis.com), is developing new additives and polymers based on levulinic ketals derived from biomass by acid hydrolysis. These ketals have promise in polyurethane polyols and in polyester thermosets or thermoplastics. Among its first commercial products are a series of plasticizers said to be “drop-in” replacements for phthalates in PVC, including both general-purpose plasticizers and fast-fusing types for plastisols. These products are said to show good compatibility, plastisol viscosity stability, and resistance to migration and extraction.
Nucleating agents promote crystallization of PLA for better properties and faster processing. Nissan Chemical Industries, Ltd. of Japan (nissanchem.co.jp) presented a paper on its Ecopromote aromatic phosphonate nucleants, including its newest Ecopromot BD, a biodegradable version with even higher performance than previous grades. A transparency-improving nucleant is in development.
Also presenting PLA nucleants was Takemoto Oil & Fat Co., Ltd. of Japan (takemoto.co.jp). Its LAK-301 additive is used at 1% level and is also available as 30% masterbatch in Ingeo PLA.
Another area of development is hydrolysis stabilizers for PLA. Rhein Chemie, a company of the Lanxess Group in Germany, offers BioAdimide 500XT, which acts as a chain extender and melt stabilizer in PLA and other biobased polyesters (bioadimide.com). Another example is Carbodilite hydrolysis stabilizer for PLA, PET, and PBT from Nisshinbo Chemical Inc. in Japan (nisshinbo-chem.co.jp). This carbodiimide thermoplastic powder is distributed by GSI Exim America, N.Y.C. (gsiexim.com).
An additive that increases impact resistance and elongation of PLA without affecting transparency or glass-transition temperature is Chirabazol VR from Taiyo Kagaku Interface Solution Div., a Japanese maker of food additives (taiyokagaku.com).
Processors are playing a key part in expanding the role of bioplastics in packaging and durables. Mideast-based Taghleef Industries discussed its new Ingeo-based Nativia biaxially oriented (BOPLA) films. They’re made in Italy on Bruckner equipment (flat die and tenter frame) with a deckle width of 4 meters at rates of 1430 lb/hr or 7 million lb/yr. Three-layer films are made in thicknesses of 15 to 50 μ in clear, white, two-side sealable, and metalized versions.
Applications include films and lidding for fruit, vegetable, bakery, dairy, meat, and fresh flower packaging; candy twist wrap; paper lamination; and labels. In partnership with Extendo GmbH in Germany, Taghleef also is developing modified-atmosphere packaging (MAP) films for meat and cheese.
Celplast Metallized Products Ltd., Toronto, also said it has been successful in metalizing and SiOx coating PLA films. Northern Technologies International Corp., Circle Pines, Minn., discussed its development with ITC Ltd. in India of a modified Ingeo PLA for coating onto paper. Modification raised the melt strength and reduced neck-in. The extrusion was carried out on a PE line, and the coating thickness was 23 microns, vs. 15-20μ for PE. NTIC found that PLA coating provided water and grease resistance comparable to PE.
ConAgra Foods, Omaha, said it had accomplished “the first known application of post-industrial recycled content in a PLA shrink film.” ConAgra worked with its film producer and converter to develop PLA shrink bands/sleeves using a cast film and tenter process. Recycle content is 25-60%
Control of gels and inclusions has no negative effect on high-quality graphic printing. Each test showed that rPLA shrink film performed as well as or better than the PETG or PVC film it replaced, in terms of oil resistance, machinability, tensile strength, and shrink properties.
The company now has a comprehensive strategy to convert all relevant films to PLA. In general, ConAgra prefers PLA for shrink bands because it is stiffer, allowing lighter film gauge, and lower in density, providing more packages per pound of resin. In addition, it allows a 20% reduction in shrink-tunnel temperature, making for a cooler plant environment.
In the durables sphere, two speakers at the conference produce biobased building products. LG Hausys Ltd., a materials development and fabricating division of Korea’s LG Group, is said to be the largest building-materials company in that country. It set out to replace PVC in building products with PLA-based materials using existing PVC equipment for extrusion, calendaring, and printing.
First, it had to overcome amorphous PLA’s low heat resistance, brittleness, low melt strength, narrow processing window, and susceptibility to hydrolysis. Its solutions combined chain extension to increase molecular weight and melt strength; chemical foaming to provide softness; mechanical blending with crystalline PLA for shrinkage control and wider calendaring window; and partial chemical crosslinking to add elasticity and increase plasticizer uptake and retard plasticizer migration.
The end result was flooring and wallpaper, both solid and foamed. They are said to have lower VOC emissions than PVC.
Here in the U.S., Bio-Plastic Solutions LLC, Blooming Prairie, Minn., started out as a custom profile extruder in 2000 and began exploring biobased materials and application development in 2003. President Gary Noble was looking for alternatives to PVC and formaldehydecontaining materials to satisfy demands from schools and hospitals, among others. One window company, for example, is looking to eliminate all PVC within the next five years, Noble said.
His first commercial products emerged in late 2010—proprietary PLA blends called BioBest, aimed at interior building profiles (wall and corner guards), furniture profiles (edge bands for tables and work surfaces), and molded products. They are processed on PVC equipment. These ductile materials match the performance profile of PVC and ABS, but Noble also developed BioBest composites using wheat straw that can exceed conventional materials in strength and heat resistance. Interior window and door profiles are the next big opportunity, he believes.
His BioBest products also include flat wall surfaces and office panels. The latter can incorporate printed PLA fabric over recycled cardboard or biocomposite.
Noble notes that biobased building materials have a chance to compete if their cost premium is no more than 5% to 15%. That can be partly offset by tax credits for LEED certification by the International Green Building Certification System or government purchasing preference under the USDA BioPreferred Program.
Machine-direction orientation is still discovering new market opportunities. But the technical difficulties are so great that some big projects never came of age. New equipment could make it easier.
Gels are an unsightly but common problem in single-screw extrusion.
Die buildup, also called die drool, die bleed, or plate-out, can plague any extrusion process.