Process for producing boron nitride felt

Abstract

A novel process for producing a thin flexible self supporting boron nitride felt comprising the following steps .[...]..Iadd.: .Iaddend. A. purifying boron nitride fiber by washing with water and subsequently extracting with an aliphatic alcohol containing from 1 to 3 carbon atoms.Iadd.;.Iaddend. B. forming a mat from the fibers in step A and incorporating therein an aqueous solution of an inorganic water soluble binder selected from the group consisting of water soluble halides, nitrates, nitrites and carbonates of the alkali metals, the alkaline earth metals, the Group III A metals and their mixtures; and C. drying the resulting binder.Iadd.-.Iaddend.containing mat obtained from step (B) at a temperature below the melting point of the salt.

We claim: 
     
       1. A process for producing a thin, flexible, integral boron nitride felt comprising the following steps: A. purifying boron nitride fiber by washing with water and subsequently extracting with an aliphatic alcohol containing from one to three carbon atoms;   B. forming a mat from the fibers in step (A) and incorporating therein an aqueous solution of a binder .[.in an amount such that the final concentration of the said binder in the mat ranges from about 2 × 10 -   2  to about 5.5 × 10 -   2  g/cm 2  .]., said binder being an inorganic salt selected from the group consisting of water soluble halides, nitrates, nitrites and carbonates of the alkali metals, the alkaline earth metals, the Group III A metals, and their mixtures; and   C. drying the resulting binder-containing mat obtained from step (B) at a temperature below the melting point of the salt.   
     
     
       2. The process in claim 1 wherein the binder in step (B) is incorporated by adding an aqueous suspension of the boron nitride fiber to a saturated aqueous solution of the binder, and forming the mat therefrom. 
     
     
       3. The process in claim 1 wherein the binder in step (B) is incorporated by spraying the mat formed from boron nitride fiber with an aqueous solution of the binder. 
     
     
       4. The process in claim 1 wherein the inorganic salt consists of a eutectic mixture of lithium chloride and potassium chloride.