Basics PHA – a polymer
Basics PHA – a polymer family with challenges and opportunities At the beginning of the 21 st century the chemical industry undergoes an accelerated and revolutionary change in the conversion from hydrocarbons to carbohydrates as feedstock. In 2016 it is still small (about 12 % of the chemical industry is based on carbohydrates feedstock), but growing very fast. New chemical platforms are being brought to the market, but still have to prove themselves (like succinic acid, levulinic acid and CO 2 as examples). Both industrial biotechnology (biocatalytic conversion, fermentation, downstream processing) and traditional chemo-catalytic conversion are applied to convert renewable feedstock to useful chemicals and polymers. In this process one sees significant changes in the traditional value chains for chemicals and polymers. Companies in the wood, paper, potato, other-agricultural and sugar industries with strong positions in carbohydrate feedstock and expertise in industrial biotechnology started to diversify into these traditional chemical value chains. Also companies active in waste management (both solid waste, waste water and gas effluents) work to upgrade the value of their waste streams (CH 4 biogas, fatty acids, CO 2 and also waste cooking oil), thus starting to set up after-use value chains for a circular economy. A challenge at the start of it all is that: Value chains combine competencies that have never been associated before Switching to carbohydrates as feedstock implies a tremendous innovation promise for the chemical industry. On the other hand it takes 15 – 20 years for new chemicals or polymers to become very significant in size, since new applications come one at the time, while drop-ins penetrate much faster if they are cost competitive. An industrial PHA polymer family platform is being developed since about 25 years now. The platform consists of a large variety of polymers, each with completely different properties and based on all raw material sources mentioned above. Figure 1 shows several PHA polymer examples. The simplest member, PHB, and its building block 3HB have apperared in nature for more than 3 billion years already and are part of the metabolism of many organisms for energy storage and nutritional value. PHA products range from amorphous to highly crystalline and go from high-strength, hard and brittle to low-strength, soft and elastic, so there is a large property design space for PHAs. In figure 2 a few differences between some PHA products are illustrated. However, there are more than hundred different known building block compositions for PHAs. The 3HA building blocks in PHA create sensitivity for molecular chain scission starting at 160 °C and accelerating at higher temperatures causing a loss of mechanical properties. This limits the polymer melt temperatures for processing like compounding, extrusion and injection moulding. There are also 4HA building blocks, like 4HB and 4HV, which might have a positive effect on this temperature sensitivity and so on the polymer processing window, but that still is hypothetical at this stage. During the last decade large scale PHA manufacturing plants have been built, varying in size between 5,000 and 50,000 tonnes/annum, but it has been troublesome to build demand for them and to get them base loaded. In 2009 PHA capacity expansion plans for 2015 totaled 920,000 tonnes/annum for all players together, but global sales volume was still about 1,000 tonnes/annum in 2013. scl-PHAs P3HB, P4HB, PHBV, P3HB4HB, PHB3HV4HV. CH 3 O CH 3 O CH 3 O C 2 H 5 O O O O x x O O O y x P3HB P3HB4HB PHBV y mcl-PHAs PHBH, PHBO, PHBD. CH 3 O C 3 H 7 O PHBH: O O x y lcl-PHAs Many varieties possible. scl: short chain length mcl: medium chain length lcl: long chain length In addition PHAs have been designed with aromatic or C=C groups in the side chain. Figure 1: The PHA products platform is very diverse. O C 7 H 15 O 65 O C 5 H 11 O 15 O C 15 H 31 O O 10 C 9 H 19 O 10 38 bioplastics MAGAZINE [03/16] Vol. 11
Basics By: Jan Ravenstijn Senior consultant Biopolymers and Industrial R&D management Meerssen, The Netherlands In 2015, however, the PHA scene began to turn around: more players became active at an industrial level, lower PHA prices were being offered, sales volume began to develop and a large number of value chain alliances across the whole value chain came about. All these accelerated the global market acceptance and penetration of PHA products. Today there are more than 30 companies active in development, manufacturing and scale-up of PHA products. Several of those decided to make and market their own PHAcompounds since they do not always have good experiences working with compounding companies. A CEO of one of the companies mentioned: “Most compounders do not properly process my PHA polymers, despite instructions on how to do it, so I decided to develop and to produce compounds myself and bring those to the market”. The PHA polymer platform development has been dominated by Technology Push for a long time based on a “Look what we can do” attitude and backed by local and by country governments appreciating the environmental benefits and often the start of an after-use value chain, but without sufficient understanding of the requirements for Market Pull. Often the golden rule for a new polymer was ignored: Build demand before you build capacity The last five years also several players came to the market demonstrating the understanding for the need of a broad range of applications at a competitive market price. Although they admit that their cost position will not be optimal in the first years, they show faith in where they can be when the technology is at large industrial scale, like 100,000 tonnes/annum plants. Manufacturing cost quotes of EUR 1.20/kg have already been given based on which PHA polymer pricing could be between EUR 1.60 and EUR 2.00/kg in such case. Prices of the fossil-based polymers PHA competes with currently run between EUR 1.10 and EUR 2.00/kg. So the PHA prices are still high in the range, but close enough to get significant market penetration from a polymer cost perspective. However, there are also PHA suppliers who are more careful to indicate where they think the ultimate market price can go. Although the PHA product family cannot fully substitute any of the traditional fossil-based polymer families, it can partly substitute many of them, so the accessible market for PHA is very large and could become hundreds of kilotonnes per annum, provided the cost/performance balance is OK. Depending on the PHA type and grade it can be used for injection moulding (see figure 3), sheet and film extrusion, thermoforming, foam, non-wovens, fibers, 3D-printing, paper coating, glues, binders, adhesives, as additive for reinforcement or plasticization or as building block in UPRs for paint or in PUR for foam. Most of these application developments (see figure 4) are embryonic or early-growth. PHAs can be used in most thermoplastic and thermoset market segments A new value chain is created for PHA polymers. Often, but not always it’s based on an after-use value chain utilizing components of a variety of waste streams. Also in other cases we see that the first few positions in the value chain (raw material, fermentative polymer production) are taken by parties who are unfamiliar with the plastics business. During the last two years about 5 companies have made significant progress in forming alliances across the entire value chain in order to accelerate their product and application developments. Companies developing PHA manufacturing technology formed alliances with OEMs, both for thermoplastics 70 Figure 2: Differences between several PHA products. Melt Temperature (°C) 200 190 180 170 160 150 140 130 120 110 100 0 PHB PHBD PHBV PHBHx PHBO PHBHx PHBO 2 4 6 8 10 12 14 16 18 20 3HA Content (mol%) Crystallinity (%) 60 PHB PHBV 50 PHBO 40 PHBHx 30 PHBOd 20 10 0 0 5 10 15 20 25 3HA Content (mol%) bioplastics MAGAZINE [03/16] Vol. 11 39
