Toray Develops Fine Separation, High Water Permeability Technology For PVDF Ultrafiltration Membrane (UF)

Toray Industries, Inc. recently announced that it has developed a new polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane with fine separation and high water permeability properties. PVDF UF membranes are used for water treatment in various fields. The new membrane effectively separates micro substances but its water permeability does not deteriorate and the material is expected to enable energy-savings and reduce costs in water treatment in a wide range of fields such as water supply, sewage and industrial waste water as well as food and beverages and pharmaceutical and medical applications. The company aims to accelerate demonstration experiments in these applications for commercialization.

Toray has been offering PVDF UF membrane TORAYFIL®, in which the company pursued high strength and high water permeability, for water treatment applications. While there has been growing expectations for fine separation and high water permeability from the perspective of energy saving and cost reduction, it is generally difficult to achieve both fine separation and high water permeability at the same time, as resistance in the UF membrane structure increases as the pore diameter becomes smaller and water permeability declines.

To solve this problem, Toray built on its technology to enhance pore diameter control while maintaining sufficient permeability and succeeded in creating innovative PVDF hollow fiber UF membrane that combines fine separation and high water permeability. The key points of this technology are as shown below:

1. Pursuing the limits of UF membrane structure using computational chemistry

Using phase separation simulation based on computational chemistry, which the company has been developing for long, Toray pursued the limits in terms of refinement of the size of pores on the surface of membrane, which is necessary for fine separation, and coarsening of pores inside membrane, necessary for high water permeability. Based on the in-situ observation of phase separation process carried out at SPring-8, a large synchrotron radiation facility, Toray was able to achieve these two layers by controlling the growth speed while accelerating the phase separation speed of the membrane surface layer and at the same time slowing down the phase separation speed inside the membrane.

2. Realizing fine separation properties and high permeability through innovative hollow fiber membrane process technology

By leveraging the proprietary hollow fiber process technology built on the experience in water treatment and artificial kidney applications for hollow fiber, Toray succeeded in controlling the phase separation speed and growth speed of both the surface and inner part of the membrane. This made it possible to overcome the existing trade-off between pore size and permeability, and enabled the realization of nano-metric sized fine pore with six times the permeability of existing membranes.

In the Toray Group Sustainability Vision, announced in July 2018, Toray has declared its mission of offering essential solution through the provision of innovative technologies and cutting-edge materials so as to balance the development and sustainability challenges faced by the world.

Under the corporate philosophy of “Contributing to the society through the creation of new values,” Toray will continue to pursue the limits of performance based on basic research and provide corroborative evidence for various applications of the new PVDF hollow fiber UF membrane, which combines the fine pore properties with high permeability.