ADDITIVES GO GREEN
T hese days, it seems everyone wants to be seen to be "green," and, given increasing demand from consumers for products that are biodegradable, renewable, and less dependent on fossil fuels, plastics ...
These days, it seems everyone wants to be seen to be “green,” and, given increasing demand from consumers for products that are biodegradable, renewable, and less dependent on fossil fuels, plastics processors are certainly no exception.
The high expectations shared by processors for biopolymers — materials derived at least in part from biological activity — are being satisfied by a slew of new bio-based or “all-natural” additive masterbatches, fillers and colourants, designed for use in biopolymers such as polylactic acid (PLA), as well as other eco-friendly plastics.
GETTING TOUGH ON PLA
Stiff, strong and clear, bio-based and biodegradable PLA is a popular choice among processors and end-users looking for environmentally friendly plastics. The material also poses problems, however. Brittle and offering low heat resistance, it has low melt strength and high sticking tendency during processing, and can degrade quickly in the presence of moisture.
Several additives firms have recently introduced products to address these concerns.
Clariant Masterbatches offers several different functional ingredients its new CESA-natur product line, which is designed to improve PLA melt strength and allow larger and more stable bubbles during extrusion, even at higher line speeds. According to Clariant, the product also produces smaller and more resilient cells in foamed PLA. CESA-natur uses a chain extender called CESA-extend to re-link polymer chains broken by degradation in PLA.
The additives can also be formulated for use in conventional polymers as alternatives to non-renewable additives.
CESA-natur masterbatches include slip/antiblock agents, UV/light stabilizers, antioxidants and antistatic agents, and feature a biopolymer carrier resin. According to Clariant, CESA-natur slip additive masterbatches are based on naturally occurring waxes, and perform well in PLA film applications, with only a marginal influence on transparency.
The company’s CESA-natur light masterbatches, meanwhile, are designed to provide light stabilization in both conventional resins and biopolymers, and can also function as UV filters to protect the contents of packaging made of PLA. Based on aromatic molecules, CESA-natur light additives use naturally occurring ingredients, and Clariant claims to offer improved UV protection with this masterbatch series. “In the past, the natural compounds chosen for UV protection have been coloured and usually show low thermal stability at processing temperatures above 200C,” the company said. “The newest CESA-natur light masterbatches, however, are formulated from light-coloured substances that are substantially more heat stable and offer UV protection comparable to conventional synthetic UV absorbers.”
Arkema is also attempting to tackle problems relating to the processing and performance of PLA. The company recently released two impact modifiers based on familiar core-shell technology, designed to double the toughness of PLA.
Biostrength 130 and Biostrength 150 are core-shell impact modifiers for PLA. Biostrength 130 is intended for use in translucent or clear applications, while Biostrength 150 is a higher efficiency modifier for use in opaque applications.
According to Arkema, both additives double the Gardner Impact at loadings as low as two per cent.
The company’s Biostrength 700, meanwhile, is a clear acrylic copolymer that enhances processability of PLA for use in sheet extrusion, calendering, blow molding, thermoforming and foamed applications, and also doubles the melt strength at four per cent loadings. Improved melt strength and melt elasticity provide a wider processing window for extrusion, reduce parison thinning in blow molding, assist deep-draw thermoforming, and provide a more consistent cell structure in foams.
PolyOne Corporation recently launched two new additives for biopolymers, one of which is also designed to enhance PLA. OnCap BIO Impact T is a transparent impact modifier masterbatch for PLA intended to increase the impact resistance of the base polymer while maintaining transparency.
Based on 100 per cent renewable resources, the company’s OnCap BIO Anti-fog T, meanwhile, is designed to prevent the occurrence of fogging on the surface of film packaging, enhancing the shelf appearance of chilled, pre-packaged foods. Also, by preventing the formation of small water droplets, the additive can extend product shelf life by preventing food deterioration, PolyOne said.
Another traditional challenge of molding with PLA has been achieving bright, lasting colours. Here, too, improvements are on offer.
Teknor Color Company recently released three series of colourants for use with PLA resins and blends, designed to help manufacturers of packaging, bags, liners and other extruded or injection molded products that are biodegradable and based on renewable resources. The company’s PLA-carrier concentrates are for use in all biodegradable applications; the biodegradable co-polyester-carrier concentrates have a petrochemical carrier resin and are recommended for biodegradable blown film and other applications requiring greater flexibility than is produced by 100 per cent PLA formulations; and its PETek polythylene terephthalate (PET)-carrier concentrates are for non-degradable applications where use of a biopolymer base resin such as PLA is desired, such as toys or housewares.
Concentrates in all three series are available as customer formulations in a wide range of colours, according to John Politis, director of marketing.
Clariant Masterbatches is also stepping up to the challenge of colouring PLA, as well as other biopolymers. The company’s RENOL-natur colour masterbatches are designed not only for PLA, but also for polyhydroxyalkanoates (PHAs) and starch-based materials. According to the company, the RENOL-natur Series contain only natural, renewable and completely biodegradable resins and colourants derived mainly from plants. The colours include red (derived from the cochineal insect), orange (derived from the turmeric spice plant), yellow (derived from a tropical flower) and green (derived from chlorophyll and other plant sources).
The RENOL-natur line complements the company’s Enigma colour and masterbatches, aimed at removing the murky grey colour that often comes with recycled resins, particularly in bottles using high levels — up to 100 per cent — of post-consumer recycled (PCR) high density polyethylene (HDPE). Available in translucent blue, red pearl and green pearl, these additives are designed to product bright colour with high PCR levels.
FLAME RETARDANTS, WPCs AND MORE
Also dipping a green toe in the water is Chemtura Corporation. Under the slogan “Greener is Better”, the company has introduced several new bio-based additives.
Mark OBS (organic-based stabilizers), intended for flexible polyvinyl chloride (PVC) automotive and flooring applications, are described as the industry’s first non-heavy metal heat stabilizers, and as being more cost-effective as a stabilizer than calcium zinc.
The company’s Weston NPF 705 is a drop-in liquid replacement for tris(nonylphenyl) phosphite (TNPP), an industry-standard secondary antioxidant used in linear low-density polyethylene (LLDPE) and HDPE applications such as consumer and industrial packaging, and household goods.
Naugard 300-E styrene monomer inhibitor, which uses dinitro-type polymerization inhibitor (DNBP) for scavenging of radicals, is designed to control and improve the efficiency of styrene monomer processing, especially compared to Tempo-based products.
In the realm of flame retardants, the Firemaster 800 Series for flexible PU foam are 10 per cent more efficient than the company’s predecessor additives. Each has been designed to provide a good environmental profile and is non-scorching in such applications as automotive and furniture manufacturing.
Chemtura is also tapping into the growing wood pl
astic composite (WPC) market with its Polybond 1103 and Polybond 3029 coupling and lubricating agents, designed to allow the use of more recycled wood in the composite.
Arkema Canada Inc. (Oakville, Ont.); www.arkemagroup.ca; 800-567-5726
Chemtura Corporation (Middlebury, Conn.); www.chemtura.com; 203-573-2000
Canada Colors & Chemicals Ltd. (Toronto); www.canadacolors.com; 905-454-6900
Clariant Masterbatches (Toronto); www.clariant. masterbatches.ca; 800-265-3773
PolyOne Distribution Canada Ltd. (Mississauga, Ont.);
Teknor Color Company (Pawtucket, R. I.); www.teknorapex.com; 800-556-3864