Fibres for use in ion-exchange media

Advances in Textiles Technology, May, 2008

Japanese workers have developed fibres that contain embedded particles of an ion-exchange resin and are designed specifically for use in filter media. Toyota Boshoku KK and its majority shareholder Toyota Motor reveal details of their joint development in European Patent Application EP 1 878 815.

Their aim is to overcome some of the difficulties associated with the use of ion-exchange resins that absorb water which subsequently freezes, causing the resins to break due to the stress caused by the expansion of the frozen liquid. Embedding the particles in the base resin, rather than adhering them to the surface, helps to inhibit any expansion, and so reduces breakages, as well as preventing the ion exchange particles being removed from the media so reducing its effectiveness.

To reduce the potential expansion, the diameter of the particles should be no bigger than 10 [micro]m, the Patents says. However, if the particles are too small, the distance between them in the embedded media is too great and the efficiency of the ion-exchange function is reduced. Therefore, the Patent recommends the particles are 5-10 [micro]m in diameter.

To make sure that the filter media is stiff enough to remain stable, the fibres should have a diameter of 20 [micro]m or more. At the same time, in order to make the weight per unit area sufficiently high for an effective ion exchange, the fibres should be no bigger than 50 [micro]m in diameter.

The base resin is hydrophobic such as polyester, polyamide or a hydrophobic thermoplastic. The Patent specifically notes that polyester or, preferably, polypropylene be chosen. Polypropylene gives the fibre an excellent reistance to both acids and alkalis.

In order to optimize the efficiency of the exchange, the dust retention and the pressure drop across the filter media, the Patent recommends that nonwovens made from the fibres should have basis weights of 50-500 [g.m.sup.-2].

Toyota Boshoku is a major manufacturer of filtration products and is one of 50 major companies profiled in Automotive Filters--Optimizing Performance and Minimizing Environmental Impact, the latest report to have been published by International Newsletters Ltd.

For further information, contact: Toyota Boshoku Corp, 1-1 Toyoda-cho, Kariya-shi, Aichi, Japan. Tel: 566-236611. Fax: 566-260400. E-mail: soumu@toyota-boshoku.co.jp; http://www.toyota-boshoku.co.jp; or: Guy Kitteringham, Sales and Marketing, International Newsletters Ltd, 9a Victoria Square, Droitwich Spa, Worcestershire, WR9 8DE, UK. Tel: 870 165-7210. Fax: 870 165-7212. E-mail: sales@intnews.com;http://www.technical-textiles.net/htm/w20080212.217841.htm