May 2020

Low-Cost Bioplastic to Reduce Plastic Waste

Against a background of growing concerns about marine litter and microplastic pollution, a Japanese company has developed a technology for the mass production of eco-friendly and biodegradable plastic products at low cost. The technology enables the low-cost manufacturing of polylactic acid products from corn starch or sugarcane and is attracting attention around the world.

Plastic products made from oil, such as PET bottles and food trays, are widely used around the world. Disposal of these plastics affects ecosystems because if the products are burned, they contribute to global warming, and if they flow out into the sea, they create marine litter and microplastic pollution. The World Economic Forum announced in 2016 that by 2050, the amount of plastics drifting in the sea around the world is projected to surpass the amount of fish in terms of weight.

In this situation, biodegradable plastics are attracting attention as a replacement for the current plastics made from oil. Biodegradable plastics are considered to lessen the environmental load because they are ultimately decomposed into carbon dioxide and water by microorganisms in the natural world. Polylactic acid, one of the biodegradable plastics, which is made from corn starch or sugarcane, began to be used as a material for products such as dishes and garbage bags about twenty years ago. However, polylactic acid was hard to process and products made from it were so expensive that they did not become popular at all.

Komatsu Michio, the president of Komatsu & Associates, a professional engineer’s consulting firm in Iwaki City, Fukushima Prefecture, overcame the processing challenges and developed a technology of mass-producing polylactic acid products at lower cost than by using existing methods. The main reason why polylactic acid is hard to process is that it is far more viscous than plastics made from oil. Generally speaking, to process plastics, a method called injection molding is used, which involves heating and melting plastics, injecting the molten plastics into a mold, putting them into a shape, waiting for them to cool down and solidify, then ejecting them from the mold. In the case of highly viscous polylactic acid, however, the materials do not flow to the end of a mold cavity by normal injection molding, and the article cannot be molded well.

To solve this problem, Komatsu focused his attention on a super critical phenomenon. Matter can exist as a solid, liquid or gas according to the temperature and pressure conditions. But if you keep applying pressure and heat to matter, it will enter a super critical phase in which it is indistinguishable from a gas or a liquid.

“Matter in a super critical phase is called super critical fluid and has both the diffusiveness of a gas and the solubility of a liquid. By mixing carbon dioxide in a super critical phase into melted polylactic acid, we succeeded in increasing the fluidity of polylactic acid,” explains Komatsu.

Molding polylactic acid had another significant issue. Ordinary plastics gradually solidify when they cool down, whereas a heat-resistant grade of polylactic acid contracts rapidly when it reaches a certain temperature. Once it reaches this state, it is caught in the mold core and impossible to eject. Because of this, it takes a lot of time and effort to get the molded article out, and articles cannot be produced at the same pace as ordinary plastics.

Komatsu also overcame this issue by making use of his experience of working as a mold expert for a leading electronic parts manufacturer.

“I put an infrared temperature sensor in a mold and measured the temperature of the polylactic acid in units of thousandths of a second. After repeating the measurements many times, I found that as soon as the temperature falls to 110˚C, the polylactic acid begins solidification. I found that the polylactic acid could be detached easily by capturing that timing and injecting air into the gap between the mold and the polylactic acid article,” says Komatsu.

Komatsu demonstrated his technology at K 2019, the world’s largest trade fair for plastics and rubber, in Düsseldorf, Germany in October 2019. Specifically, Komatsu demonstrated a technology for molding thin champagne glasses developed in collaboration with plastic injection molding machine manufacturers in Japan. The demonstration attracted a lot of attention from visitors.

In April 2020, Komatsu won the Technology Award 2020 from The Japan Society for Die and Mold Technology, a prestigious award granted in the field of die and mold technology. His technology has been granted numerous patents in Japan and overseas.

In January 2018, the European Union (EU) proposed putting an all-out ban on all inter-regional disposable plastic containers by 2025 and declared that it would aim to make all inter-regional plastic packages recyclable by 2030. The demand for biodegradable plastics as materials to cope with these environmental regulations is expected to grow. Orders for Komatsu’s biodegradable baby tableware, for example, are pouring in from Europe and other countries as well as Japan.

“We still have an issue in terms of the high material costs. But we have recently seen an increase in the number of polylactic acid manufacturers and production volumes, which leads to lower costs. In this situation, I think that products using polylactic acid will gradually become popular. I will be extremely happy if the technology I developed helps preserve the natural global environment,” says Komatsu.

(This is a revised version of the article that appeared in the November 2019 issue of Highlighting Japan.)