Toray Industries, Inc.

Akito Kuroda

Yoshikazu Yakake

Yukihiro Matsuzaki

Satoshi Yanagisawa

Masaru Ueno

Yuji Iyama

Hajime Nishimura

Katsuya Okajima

Tomoharu Hirose

Koji Yamano

Yu Matsuoka

Provided are a mixed-fiber nonwoven fabric suitable for air filters and a filter medium using the mixed-fiber nonwoven fabric. The nonwoven fabric includes at least two types of fibers having different melting points, which fibers are low melting point fibers made of a polyolefin resin component A, and high melting point fibers made of a high melting point resin component B having a higher melting point than that of the polyolefin resin component A. The number average fiber diameter of the high melting point fibers is larger than that of the low melting point fibers. At least one high melting point fiber having a fiber diameter of 20 &#x3bc;m to 100 &#x3bc;m is present per 1.00 mm of the length of the cross section of the nonwoven fabric. The number average fiber diameter of all fibers constituting the nonwoven fabric falls within the range of 0.3 &#x3bc;m to 10 &#x3bc;m.

Mixed-fiber nonwoven fabric, laminated sheet and filter, and process for producing mixed-fiber nonwoven fabric

A nonwoven fabric includes mixed fibers having different fiber diameters. A group of fibers having a fiber diameter of 5.0 &#x3bc;m or less (fiber group A) is present at a volume fraction of 20 to 80 vol %, a group of fibers having a fiber diameter of 50.0 &#x3bc;m or more (fiber group B) is present at a volume fraction of 1 to 40 vol %, and a group of fibers having a fiber diameter of more than 5.0 &#x3bc;m and less than 50.0 &#x3bc;m (fiber group C) is present at a volume fraction of 0 to 79 vol %. The ratio of the median fiber diameter (B') of fiber group B to the median fiber diameter (A&#x2032;) of fiber group A (B&#x2032;/A&#x2032;) is 35 or more.

Mixed-fiber nonwoven fabric and filter medium using the same

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Otsu, Japan

Akito Kuroda