Shrink-resistant refractory fiber and process for making same

Claim 2

A shrink resistant flexible ceramic fiber comprising a microcrystalline combination of alumina and silica manufactured by forming amorphous fibers from a melt containing from about 40 to about 65 weight percent alumina and from about 35 to about 60 weight percent silica followed by heating the fibers to a sufficient temperature for a sufficient time to form microcrystals and cooling the fibers below the crystallization temperature before macrocrystals form, said melt being essentially free from alkali and alkaline earth metal oxides and oxides of boron, lead, copper and zinc; the ceramic fiber being capable of being exposed to a temperature of 1425° C. for 24 hours with a linear shrinkage of less than 2 percent.

Claim 3

The shrink resistant flexible ceramic fiber of claim 1 manufactured by forming amorphous fibers from a melt consisting essentially of from about 40 to about 65 weight percent alumina and from about 35 to about 60 weight percent silica followed by heating the fibers to a sufficient temperature of from 1150° C. to 1240° C. and maintaining said temperature for a sufficient time of between 0 and 30 minutes to convert the amorphous fibers to microcrystalline fibers of sufficient crystallinity such that a mat formed from said fiber has a linear shrinkage of less than two percent after 24 hours at 1425° C. followed by cooling the fibers below the crystallization temperature before macrocrystals form.

Claim 4

The shrink resistant flexible ceramic fiber of claim 2 wherein said sufficient temperature is from 1200° to about 1240° C. and said fiber is heated from below 960° C. to said sufficient temperature in from 0 to about 2 minutes; and cooled to below the crystallization temperature within from 0 to 2 minutes.

Claim 5

The shrink resistant flexible ceramic fiber of claim 2 wherein said sufficient temperature is about 1200° C. and said sufficient time is between about 2 and about 15 minutes.

Claim 6

The shrink resistant flexible ceramic fiber of claim 1 wherein said sufficient temperature is about 1095° C. and said sufficient time is between about 15 and about 30 minutes.

Claim 7

The shrink resistant flexible ceramic fiber of claim 2 wherein said fiber is in a fiber mat prior to heating.

Claim 8

A process for the manufacture of a shrink resistant flexible ceramic fiber which comprises: (a) melting from about 40 to about 65 weight percent of alumina with from about 35 to about 60 weight percent of silica; (b) forming fibers from the melt; (c) rapidly solidifying said fibers to form amorphous fibers; (d) heating the fibers to a sufficient temperature of from 1150° C. to 1240° C.; (e) maintaining said temperature for a sufficient time of between 0 and 30 minutes to convert the amorphous fibers to microcrystalline fibers of sufficient crystallinity such that a mat formed from said fiber has a linear shrinkage of less than two percent after 24 hours at 1425° C.; and (f) cooling the fibers to below the crystallization temperature before macrocrystals can form.

Claim 9

A process for the manufacture of a shrink resistant flexible ceramic fiber which comprises: (a) melting from about 40 to about 65 weight percent of alumina with from about 35 to about 60 weight percent of silica; (b) forming fibers from the melt; (c) rapidly solidifying said fibers to form amorphous fibers; (d) heating the fibers to a sufficient temperature of from 1150° C. to 1240° C.; (e) maintaining said temperature for a sufficient time of between 0 and 30 minutes to convert the amorphous fibers to microcrystalline fibers of sufficient crystallinity such that a mat formed from said fiber has a linear shrinkage of less than two percent after 24 hours at 1425° C.; and (f) cooling the fibers to below the crystallization temperature before macrocrystals can form.

Claim 10

The process of claim 7 wherein said sufficient temperature is between 1200° C. and 1240° C.; said fiber is heated from below 960° C. to said sufficient temperature in from 0 to about 2 minutes; and said fibers are cooled to below the crystallization temperature within from 0 to 2 minutes.

Claim 11

The process of claim 7 wherein said fibers are formed by spinning, extrusion or blowing.

Claim 12

The process of claim 7 wherein said sufficient temperature is about 1200° C. and said sufficient time is between about 2 and about 15 minutes.

Claim 13

A process for the manufacture of a shrink resistant flexible ceramic fiber according to claim 1, which comprises: (a) melting from about 40 to about 65 weight percent of alumina with from about 35 to about 60 weight percent of silica; (b) forming fibers from the melt; (c) rapidly solidifying said fibers to form amorphous fibers; (d) heating the fibers to a sufficient temperature of about 1095° C.; (e) maintaining said temperature for a sufficient time of between about 15 and about 30 minutes to convert the amorphous fibers to microcrystalline fibers of sufficient crystallinity such that a mat formed from said fiber has a linear shrinkage of less than 2 percent after 24 hours at 1425° C.; and (f) cooling the fibers to below the crystallization temperature before macrocrystals can form.