Focus on Resins: NTL Chemical Consulting | 29


this resin. However, I have heard that some particleboard and MDF makers in Europe are currently trying tannin-based formulae.” Plywood, with less susceptibility to these problems, remains a suitable candidate for ‘green’ bio-based, sustainable based resins, for instance soya bean, said Mr Pargianas. Soya bean was being widely used for


plywood production in North America for several years. Lignin is also commonly used in the plywood industry, he added. Latvijas Finieris, a plywood producer in Latvia, has successfully used lignin in its production. However, due to its rapid drying, the content of lignin in the resin is still a maximum of about 50%, said Mr Pargianas. Phenolic resin is used for the other 50%. “But the volume of plywood production is much less [than MDF or particleboard],” he said.


“Finnish particleboard maker Koskisen Oy has reportedly used lignin successfully, but without any indication of the estimated final production cost per cubic metre,” said Mr Pargianas. “Soya and the cross-linking agent PAE (polyamide epichlorohydrin) have been tried by several particleboard and MDF producers, including a plant in South Korea, where the best results in terms of all board properties were obtained when a mixture of about 50/50 soya and PAE cross-linker were used. However, this is a very expensive solution,


since PAE’s cost is several times higher than soya bean resin,” he said. Of course, pointed out the managing


director, isocyanate is almost formaldehyde- free and is widely used in the production of OSB (at least in the core layer) and with annual plants such as straw boards. It has also been used in small amounts in particleboard core layers to accelerate the line speed and, in a few cases, in MDF – mainly for the production of moisture- resistant boards. The isocyanates create strong bonds and significantly improve wet properties. Their disadvantage is their high cost, as well as the problem of adhesion of the isocyanate to press platens or belts, requiring the use of release agents, which are also quite expensive. “In terms of bio-based or ‘green’ resins, other than tannin and lignin, there has been a lot of work based on, for example, modified starch, at both laboratory and industrial scale,” said Mr Pargianas. “However, all these resins require some cross-linking agent, and, in most cases, there was poor cross-linking, which caused low reactivity, leading to production speed and board performance problems, especially with regard to moisture/thickness swelling performance. “EcoSynthetix, Evertree and Sestec in Europe have all produced particleboard and


MDF from protein-based resins, using starch, sunflower, rapeseed oil cakes, etc, which are by-products of the vegetable oil refining process. “However, this has involved significantly increased final costs per cubic metre, compared with commercially used UF resins.” Mr Pargianas also said that animal blood had been used to make particleboard in Europe, but it was unsuccessful due to the terrible stench given off by the manufacturing process – and the finished boards!


He pointed out that there is another


consideration with using protein and starch, or any other food crop-based resin, and that is the potential disruption to the food chain if it became widely used by the panel industry. Though some the materials are from crop waste. “We have also tried, at laboratory scale, a few modified grades of starch and proteins, with cross-linkers, in both particleboard and MDF, but to obtain good board properties, we needed to significantly increase the amount of binders and cross-linkers and, in most cases, we also needed to significantly extend the pressing time. Despite this, in most cases, the water absorption and thickness swelling in the final board was quite high,” said Mr Pargianas. The problem with starch is that it is not


water-soluble, so how do you spray it? It can cause problems with the spray nozzles in the blowline and so you probably will need some kind of dispersion system. “However, in particleboard, it is possible to use modified starch, partly in powder form,” said Mr Pargianas. “So far, bio-based resins still have


considerations, both in terms of panel performance and in protein or starch availability. As a niche product it is OK, but in big volumes? That is very difficult.” Mr Pargianas went on to say that NTL is


trying to use certain by-products (which are an NTL secret), which will substitute existing


resins up to a certain level. So far, he said, that level stands at 30%, but NTL is trying to go higher. He believes that any substitute resin needs


to not be in the food chain, but to be a ‘waste product’ – and to be relatively cheap. “You can have ‘green’ formaldehyde resins,


derived for instance from ‘green hydrogen’ or from bio-gas (methane) to produce methanol and urea instead of from natural gas,” said Mr Pargianas, “But it is quite an expensive process. For the future, I foresee that formaldehyde will continue to be used – we can already produce boards with the formaldehyde level of natural wood. “I believe that hybrid resins, using partly green, bio-based adhesives in combination, for example, with isocyanates or other cross-linkers and partly formaldehyde-based resins, are the future. “For the time being, phenol formaldehyde resins and UF or MUF resins, in combination with isocyanates, already exist, but the trend will be for expansion of their use, producing ‘Super E-Zero’ boards at good line speeds. And it is cost-effective.” Mr Pargianas went on to say that tannin- and lignin-based resins can be the future if they are modified and cross-linked. But, as they are food products, protein- and starch- based resins can only, in his opinion, be used as niche products. “Formaldehyde-based resins are still the


most cost-effective option, but our aim is to progressively move from hybrid systems to 100% bio solutions,” said Mr Pargianas. “Our R&D department is dedicated to advancing green and bio resin technologies, while ensuring sustainability and cost- effectiveness. Our focus lies in not disturbing the food chain, but utilising natural by- products with low value, coupled with innovative cross-linkers. “Faster and cheaper will forever be the requirement [of the panel manufacturing industry],” concluded Mr Pargianas. ●


Above: NTL has done extensive testing on bio-based resins www.wbpionline.com | April/May 2024 | WBPI


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