Recently, Japan's Sanyoshi Lacquerware (Sanyoshi) introduced a 0.53mm-thick transparent cup made of polylactic acid (PLA). According to the company, this is the world's thinnest plastic cup made from PLA injection molding. The thin-walled PLA cups have been branded "IZ EARTH" by the Sanji Lacquer Shop. Sales are expected to begin after the spring of 2024.
Although PLA is widely used in food packaging and tableware applications, problems with its fluidity when melted have plagued manufacturers. Using conventional injection molding techniques, it is difficult to manufacture thin-walled products with wall thicknesses of less than 1 mm. In addition, PLA has a high raw material cost compared to petroleum-derived polystyrene and polyolefins, and increasing the thickness of the product to improve fluidity would result in an increase in cost beyond the retail price range. As a result, global sales of PLA injection molding products are limited.
In order to solve these problems, SANYI Lacquerware Co., Ltd. entered into a patent licensing agreement in cooperation with Mr. Michio Komatsu (Director of Komatsu Engineer's Office). Mr. Komatsu holds a patent for a unique manufacturing process that enables the injection molding of thin-walled containers using PLA. In order to realize this, the company built a factory integrating research and production at its head office in Aizuwakamatsu, Fukushima Prefecture.
The development of this technology has resulted in the remarkable success of the world's thinnest PLA (0.53mm) transparent container. This breakthrough was achieved using three innovative methods: first, by instantly dissolving a large amount of CO2 in a supercritical state into PLA, its flowability was effectively improved; second, by using a valve gate to directly fill the cavities, the smooth molding of the thin-walled containers was ensured; and lastly, by cooling the molds (8 cavities) in a rapid manner, CO2 foaming was effectively suppressed, and the continuous production of the 8 transparent containers was achieved.
In order to commercialize this technology, a range of specialized equipment is operated in an integrated and synergistic manner. A dedicated injection molding system, supercritical fluid generator, particle pre-treatment unit, mold temperature control system, and valve gate system work together to ensure the smooth operation of the world's top injection molding line for thin-walled containers of PLA. The successful application of this technology will further promote the widespread use of PLA in food packaging and tableware, reducing costs and increasing production efficiency.
