Alumina fiber aggregate, process for producing the same, and use thereof

• US 8,383,714 B2
• Filed: 08/24/2012
• Issued: 02/26/2013
• Est. Priority Date: 10/11/2007
• Status: Active Grant

• Current Assignee: Denki Kagaku Kogyo Kabushiki Kaisha (TDK Corporation)
• Original Assignee: Denki Kagaku Kogyo Kabushiki Kaisha (TDK Corporation)
• Inventors: Ohshima, Yasutaka, Hirano, Isamu, Higuchi, Takayuki
• Primary Examiner(s): LEE, DORIS L
• Application Number:
  US13/594,590
• Publication Number:
  US 20120318897A1
• Time in Patent Office: 186 Days
• Field of Search: 524/430
• US Class Current: 524/430
• CPC Class Codes: C04B 2235/526 characterised by the length of the fibers
• CPC Class Codes: C04B 2235/5264 characterised by the diameter of the fibers
• CPC Class Codes: C04B 35/62236 Fibres based on aluminium oxide
• CPC Class Codes: C04B 35/62245 rich in aluminium oxide
• CPC Class Codes: C04B 35/6261 Milling
• CPC Class Codes: C08J 5/041 with metal fibres

Abstract

A process for producing the alumina fiber aggregate which, when examined by the electron microscope method, gives a frequency distribution regarding number of fibers, wherein the number of fibers having a fiber length of 50-200 μm is 70% or more (including 100%), the number of fibers having a fiber length smaller than 50 μm is 30% or less (including 0), the number of fibers of 50-100 μm is 30-50%, the number of fibers longer than 100 μm but not longer than 200 μm is 30-50%, and the number of fibers longer than 200 μm is 20% or less (including 0). The process including the steps of grinding cottony alumina-based fibers comprising 70-100% by mass of Al₂O₃ and 0-30% by mass of SiO₂ while applying a pressure of 0.1-20 MPa thereto and then classifying the ground fibers.

Claims

1. A process for producing an alumina fiber aggregate which, when examined by the electron microscope method, gives a frequency distribution regarding number of fibers, wherein the number of fibers having a fiber length of 50-200 μ

m is 70% or more (including 100%), the number of fibers having a fiber length smaller than 50 μ

m is 30% or less (including

     0), the number of fibers of 50-100 μ

m is 30-50%, the number of fibers longer than 100 μ

m but not longer than 200 μ

m is 30-50%, and the number of fibers longer than 200 μ

m is 20% or less (including

     0), comprising the steps of;

grinding cottony alumina-based fibers comprising 70-100% by mass of Al₂O₃ and 0-30% by mass of SiO₂ while applying a pressure of 0.1-20 MPa thereto and then

classifying the ground fibers.

2. The process for producing an alumina fiber aggregate according to claim 1, wherein the classification is conducted with respect to classification points of 50 μ

m and 200 μ

m in terms of fiber length and the fibers intermediate between the two classification points are collected.

3. The process for production according to claim 1, wherein the classification is conducted with an air classifier which is based on the Coanda effect.

4. The process for production according to claim 3, wherein in the air classifier based on the Coanda effect, air having a pressure of 0.2-0.3 MPa is injected from a raw-material feed nozzle.

5. The process for production according to claim 3, wherein the air classifier based on the Coanda effect is an air classifier which has a Coanda block, a first classifying edge block, and a second classifying edge block, wherein the first and second classifying edge blocks are disposed in this order in a direction away from the Coanda block side, and which further has a first classifying edge disposed at the tip of the first classifying edge block and a second classifying edge disposed at the tip of the second classifying edge block, and

wherein the distance f1 between the vertex of the first classifying edge and the surface of the Coanda block, as measured on the straight line connecting the center point of a circle formed with the curved surface of the Coanda block to the vertex of the first classifying edge, is 10-30 mm.

6. The process for production according to claim 5, wherein f1 is 10-15 mm.

7. The process for production according to claim 3, wherein the air classifier based on the Coanda effect is an air classifier which has a Coanda block, a first classifying edge block, and a second classifying edge block, wherein the first and second classifying edge blocks are disposed in this order in a direction away from the Coanda block side, and which further has a first classifying edge disposed at the tip of the first classifying edge block and a second classifying edge disposed at the tip of the second classifying edge block, and

wherein the distance f2 between the vertex of the second classifying edge and the surface of the Coanda block, as measured on the straight line connecting the center point of a circle formed with the curved surface of the Coanda block to the vertex of the second classifying edge, is 30-50 mm.

8. The process for production according to claim 7, wherein f2 is 30-40 mm.