In organic fibers containing fine crystals of AlN and Al2 O3 and process for their production

Claim 2

An inorganic fiber composed essentially of fine crystals of an aluminum compound, which contains at least 10% by weight of aluminum nitride and the rest of the aluminum compound being alumina.

Claim 3

The inorganic fiber according to claim 1, wherein the content of the aluminum compound is at least 95% by weight and the content of other inorganic compounds is less than 5% by weight.

Claim 4

The inorganic fiber according to claim 2, wherein the content of aluminum nitride is at least 50% by weight.

Claim 5

The inorganic fiber according to claim 3, which has a diameter of not more than 20 μm and a ratio of the length to the diameter being at least 50.

Claim 6

An inorganic fiber composed essentially of fine crystals of aluminum nitride, which has a diameter of not more than 20 μm and a ratio of the length to the diameter being at least 50.

Claim 7

An inorganic fiber composed essentially of fine crystals of aluminum nitride, which has a diameter of not more than 20 μm and a ratio of the length to the diameter being at least 50.

Claim 8

A process for producing inorganic fibers composed essentially of fine crystals of an aluminum compound and containing at least 10% by weight of aluminum nitride, said process comprising: (a) spinning a viscous solution comprising an aluminum compound and an organic polymer compound to obtain precursor fibers in which the atomic ratio of organic carbon to aluminum is at least 0.5; (b) heating said precursor fibers at a temperature of at least 1,000° C. in a non-oxidizing atmosphere comprising a gas selected from the group consisting of nitrogen and ammonia to convert at least part of said aluminum compound in said precursor fibers to aluminum nitride; and (c) obtaining inorganic fibers composed essentially of fine crystals of an aluminum compound and containing at least 10% by weight of aluminum nitride, said fibers having a diameter of from 2 to 20 micrometers and a length to diameter ratio of at least 50 wherein said aluminum nitriate, aluminum acetate, and aluminum alkoxide, alumina, or an aluminum oxychloride.

Claim 9

A process for producing inorganic fibers composed essentially of fine crystals of an aluminum compound and containing at least 10% by weight of aluminum nitride, said process comprising: (a) spinning a viscous solution comprising an aluminum compound and an organic polymer compound to obtain precursor fibers in which the atomic ratio of organic carbon to aluminum is at least 0.5; (b) heating said precursor fibers at a temperature of at least 1,000° C. in a non-oxidizing atmosphere comprising a gas selected from the group consisting of nitrogen and ammonia to convert at least part of said aluminum compound in said precursor fibers to aluminum nitride; and (c) obtaining inorganic fibers composed essentially of fine crystals of an aluminum compound and containing at least 10% by weight of aluminum nitride, said fibers having a diameter of from 2 to 20 micrometers and a length to diameter ratio of at least 50 wherein said aluminum nitriate, aluminum acetate, and aluminum alkoxide, alumina, or an aluminum oxychloride.

Claim 10

The process of claim 6, comprising heating the fibers obtained in step (b) at a temperature of from 500° to 700° C. in an oxidizing atmosphere to remove carbon contained in said fibers.

Claim 11

The process of claim 6, wherein said aluminum compound is substantially the only metal compound contained in said viscous solution.

Claim 12

The process of claim 6, wherein said atomic ratio of organic carbon to aluminum in said viscous solution is from 1.5 to 2.5.

Claim 13

The process of claim 6, comprising using a temperature of from 1400° to 1700° C. in step (b).

Claim 14

The process of claim 6, comprising heating said precursor fibers in step (b) until the content of aluminum nitride reaches 95 wt.% of the inorganic fiber obtained.

Claim 15

The process of claim 6, comprising obtaining inorganic fibers having fine crystals having a size of from 0.005 to 1 micrometers.

Claim 16

The process of claim 6, comprising obtaining inorganic fibers having fine crystals wherein the size of said fine crystals is from 1/1000 to 1/5 of the diameter of said fibers.

Claim 17

The process of claim 6, wherein said inorganic fibers obtained in step (c) are made of aluminum nitride and alumina.

Claim 18

The process of claim 14, wherein said inorganic fibers obtained are composed essentially of fine crystals of aluminum nitride having a size of from 0.005 to 1 micrometers and fine crystals of alumina having a crystal size of from 0.005 to 1 micrometers.

Claim 19

The process of claim 6, comprising obtaining inorganic fibers containing aluminum nitride, alumina and less than 5% by weight of a silicon compound.

Claim 20

The process of claim 6, comprising obtaining inorganic fibers in step (c) having a diameter of not more than 10 micrometers.

Claim 21

The process of claim 6, comprising obtaining inorganic fibers in step (c) having a diameter of from 2 to about 5 micrometers and a length of at least 10 mm.

Claim 22

The process of claim 6, wherein said organic polymer compound comprises a polyvinyl alcohol, a polyethyleneglycol, a polyacrylamide, a hydroxyethyl starch, a methyl cellulose, a hydroxyethyl cellulose or a carboxymethyl cellulose.

Claim 23

The process of claim 6, comprising spinning a viscous solution in step (a) having an atomic ratio of carbon atoms in said organic polymer compound to aluminum atoms of at least 0.5.

Claim 24

The process of claim 20, wherein said atomic ratio of carbon atoms in said organic polymer compound to said aluminum atoms is from 1.5 to 2.5.

Claim 25

The process of claim 6, comprising using nitrogen in step (b).

Claim 26

The process of claim 6, comprising using ammonia in step (b).