Aromatic polyamide fiber, a method for producing the same, and protective clothing material comprising the same

1. An aromatic polyamide fiber comprising an aromatic polyamide consisting of a structural repeating unit of the following formula (1), and a structural repeating unit of the following repeating unit (2) in an amount of 30 mol % or more to the whole amount of the aromatic polyamide structural units, the fiber having strength of 20 to 26.9 cN/dtex and modulus of elongation of 500 to 900 cN/dtex:

wherein Ar 1 represents an unsubstituted or substituted divalent aromatic group, and Ar 2 represents an unsubstituted phenylene group;

wherein the fiber comprises filaments having a fineness of 0.5 to 2.2 dtex.

2. A protective clothing material comprising a layered product of a single kind or plural kinds of fiber cloths, wherein the fiber cloth is comprised of the aromatic polyamide fiber as claimed in claim 1 .

3. A method for producing an aromatic polyamide fiber, comprising extruding an aromatic polyamide solution containing a structural repeating unit of the following formula (1), and a structural repeating unit of the following repeating unit (2) in an amount of 30 mol % or more to the whole amount of the aromatic polyamide structural units from a spinning nozzle, coagulating the solution in an NMP aqueous solution having a concentration of from 10 to 50% by weight at a temperature of from 20 to 50° C., drawing the resulting fiber by 1.3 to 2.5 times in an NMP aqueous solution having a concentration of from 30 to 80% by weight at a temperature of from 20 to 50° C., and then heat-treating the resulting fiber:

wherein Ar 1 and Ar 2 each independently represent an unsubstituted or substituted divalent aromatic group,

wherein said method produces an aromatic polyamide fiber as claimed in claim 1 .

4. The method for producing an aromatic polyamide fiber as claimed in claim 3 , wherein the heat treatment temperature is from 300 to 550° C.

5. The method for producing an aromatic polyamide fiber as claimed in claim 3 or 4 , wherein tensile strength of the aromatic polyamide fiber is 21.5 to 26.9 cN/dtex, and initial modulus thereof is 570 to 900 cN/dtex.

6. The aromatic polyamide fiber as claimed in claim 1 , wherein the fiber comprises filaments having a fineness of 0.5 to 1.7 dtex.

7. The aromatic polyamide fiber as claimed in claim 1 , wherein the fiber comprises filaments having a fineness of 0.5 to 1.4 dtex.