en.Wedoany.com Reported - Osaka Metropolitan University and Fuji Pigment Co., Ltd. have jointly developed a new process for recycling colored plastics. This process encapsulates pigments in silica microspheres, enabling plastics to be repeatedly recycled while maintaining stable quality.

Colored plastics have long been considered a recycling challenge because pigments mixed into conventional recycling streams produce low-quality, turbid materials. Although current chemical decomposition methods can remove colorants, they require high temperatures of 300 to 500 degrees Celsius, resulting in significant energy consumption and environmental burden.

A team led by Associate Professor Kenji Okada and Professor Masahide Takahashi from Osaka Metropolitan University's Graduate School of Engineering used a spray-drying method to encapsulate pigments in silica microspheres—the main component of sand and glass. These heat-resistant and chemically stable capsules can withstand plastic molding processes while maintaining the color of the final product.

During the recycling stage, which is conducted at room temperature, simple centrifugal separation achieves nearly 100% efficiency in separating the colorless plastic solution from intact pigment capsules. For different colors, the researchers used capsules of varying sizes and demonstrated the ability to selectively separate colors using basic mesh sieves. Tests showed no significant degradation in color or quality after multiple recycling cycles.

Kenji Okada noted that a key advantage of this technology is the simplicity of recycling: when plastics are dissolved in solvents such as acetone, the pigment capsules remain intact. Masahide Takahashi pointed out that this method transforms colored plastics, which were previously only suitable for disposal or downcycling, into high-value resources that can be reused repeatedly. It is expected to be applicable to waste plastics such as PET bottles and polyethylene bags, contributing to a sustainable circular recycling system.