High-performance Paper Japanese Papermaking Techniques in Modern Industry What is high-performance paper? The industrial use of high-performance paper Japan's high-performance papers Future prospects INAGAKI Hiroshi Professor Emeritus, Kobe Women's University Chairman of High Performance Paper Society, Japan High-performance paper, a highly regarded and indispensable new material for high-tech industries, was developed using the traditional techniques of Japanese papermaking and by expanding the scope of raw materials from plant fibers to include synthetic, mineral, and metal fibers. What is high-performance paper? In Japanese, this paper is called kino-shi, literally "functional paper." To be truly called "functional," however, it should have feedback capabilities, as animals do. In future, high-performance paper will be required to have "functional" features, but for today, we use the term "high-performance paper" to refer to certain types of paper with high value-added in terms of quality and economy and with the enhanced performance required to meet the needs of leading-edge industries. The industrial use of high-performance paper The material is fitted to the inside of the brake. Automobile-use wet-type friction material made of high-performance paper (more than ten layers) In our daily lives, we use papers made of natural fibers for writing, printing, wrapping and wiping. But it is becoming increasingly difficult for natural fiber papers to meet the severe standards required of the industrial materials that support modern technology. Take heat resistance for example. Conventional plant-fiber paper can bear temperatures of up to only 180C. But "paper" made from heat-resistant synthetic fibers can withstand temperatures as high as 400C. Using ceramic fibers, it is possible to make paper capable of withstanding temperatures of more than 2000C. Photo 1 shows a friction material used in automobile brakes. This heat- and wear-resistant material is obtained by resin-finishing a high-performance paper containing synthetic fibers and inorganic fibers. It is no exaggeration to say that driving safety depends on this paper. Photo 2 shows the separator inside an alkaline battery. Made of alkali-proof synthetic fiber, this type of separator is used in the lithium batteries that operate small portable phones: if excessive electric current passes through the separator, it melts and halts the current. Paper is essentially a thin layer of overlapping fibers. The quality of the fiber, characteristics of the surface, and pores between the fibers are all designed to meet a variety of purposes, and the size and distribution of pores can be produced as required. One example is gas-sterilization paper. Scalpels and syringes are placed in a paper bag, and after sterilization with gas, they can be stored in ordinary air. They are maintained in their sterilized state because bacteria cannot pass through the paper. In this case, thorough quality control is required because just one hole larger than a bacterium defeats the bag's germ-free capability. The amazing development of papermaking technology in recent years has made it possible to produce papers able to meet such high quality standards. Unlike general-purpose papers, we don't see high-performance papers around us because they are incorporated into high-tech products and usually supplied directly to specific users. But their importance in modern industries is increasing as they become crucial materials which affect the performance of the products in which they are used. Japan's high-performance papers Today, 67 types of high-performance paper (categorized by function) are produced in Japan.1) As for automobile brake material such as that shown in Photo 1, one company has captured about 60% of the Japanese market. Its products are used in upmarket models produced by American and German automakers, with a high reputation for quality. One factory in Tokushima Prefecture produces more than 60% of the original paper. A company in Shikoku has about 70% of the world's market for papers for electrolytic capacitors. This company also provides separators for alkaline batteries to battery manufacturers all over the world. Thus Japan's contribution to the world's supply of high-performance papers is substantial, and it can be safely said that the country has the most advanced technology in this field. Four reasons underpin Japan's becoming the world leader in this field: 1) From washi making come the origins of high-performance paper manufacturing. Papermaking techniques were first introduced from China to Japan. About 100 years later, however, the tamezuki method, in which fibers are left to settle on a net, was improved to become the unique Japanese technique of nagashizuki. In nagashizuki, mucilage is added to the fiber solution to disperse the fibers more evenly. Moreover, the fiber-water solution is shaken on the net to disperse the long fibers and to make thin sheets of paper. From this technique comes the origin of the technology to make high-quality paper from synthetic fibers and ceramic fibers, materials not easy to form into paper. Moreover, most production centers of high-performance papers are areas which have traditionally produced Japanese paper. The inclined-wire paper machine, the most commonly used piece of equipment to manufacture high-performance papers today, was developed in the United States, but it is said a close study of Japanese papermaking methods led to its invention. 2) An advanced fiber industry supplies the raw materials for high-performance paper. Japan's fiber industries, and in particular the synthetic fiber industries, boast the world's highest levels of technology. As suppliers of raw materials for high-performance papers, they have developed advanced technologies for cutting fibers and for making fiber surfaces hydrophilic. Recently, they have developed such unique products as fibers with asymmetrical cross-sections and superfine fibers. Another notable trend is the addition of specific features, such as mildew-proof and insect-proof finishes and heat-generating fiber. The fiber manufacturers also supply carbon fibers, inorganic fibers and other materials for high-performance paper. Apart from ensuring the stable supply of materials, they have stimulated the development of high-performance paper through their own creation of new fibers. 3) The growth of modern technology-based industries has given a boost to the high-performance paper industry. The electronics, automobile, machinery and other modern high-technology industries have provided an important stimulus for the development of Japan's high-performance paper industry in the form of new requirements and severe performance testing and analysis. Capacitor paper, filters for batteries, air filters, heat-resistant paper and paper for suppressing radio interference are crucial components determining the basic performance of the equipment in which they are used. The dramatic growth of Japan's high-performance papers was prompted by such market demands. 4) An ample supply of water of suitable quality is available to make high-performance paper. The types of fiber and binder used in the manufacture of high-performance paper minutely affect the quality of the product by changing the way the fibers are suspended. The quality of water used is also important. When certain types of fiber and binder are used, it is said the products manufactured would differ if water from different water systems were used. Because Japan is a volcanic country with an ample supply of good-quality soft water, it has a tremendous advantage in the manufacturing of high-performance papers. Backed by strong and sophisticated demand, an abundant supply of raw materials to meet this demand, and such advantageous geographical conditions leading to water resources, Japan's traditional papermaking techniques have been developed into a modern technology. The importance of the Japanese high-performance paper industry will continue to grow both at home and abroad. Future prospects The development of high-performance papers will continue ever more rapidly as new products and applications continue to arise from technological advances. For example, a type of paper with a composition that changes from one surface to the other is being considered as a heat insulator on the exterior of space shuttles. Advances in the development of post-treatment are also expected. While uniformity is important in existing high-performance papers, manufacturers have begun to develop new types with fibers of different types, thickness and length, emphasizing unevenness and randomness to appeal to people's aesthetic tastes. With the cooperation of the High Performance Paper Study Group, a Danish artist has since December 1997 been conducting an experiment at a traditional paper mill 2) in Yamakawa-cho, Tokushima Prefecture. The experiment is expected to result in a project that combines aesthetic tastes with high-performance paper, and art with science. 1) New Handbook of High Performance Paper, written and edited by the High Performance Paper Study Group, 1997 2) Fuji Paper Mills Cooperative, Yamakawa-cho, Oe-gun, Tokushima Prefecture All images Copyright. 1997 Kansai International Public Relations Promotion Office. All Rights Reserved.