| 摘要 |
1. Aramid fibers having a length of 0.15 to 10 mm, a surface area of 0.5 to 20 m<2>/g and a coating of chitosan in the amount of 1 to 10%, based on the weight of the fibers. 2. The fibers of claim 1 wherein the chitosan has a 1% solution viscosity in 1% acetic acid of 10-22,000 mPa-sec. 3. The fibers of claim 1 wherein the fibers are aramid floc. 4. The fibers of claim 1 wherein the fibers are aramid pulp. 5. A friction paper comprising 5 to 95% by weight aramid fiber, 0 to 20% by weight binding material and 10 to 80%, by weight inorganic filler wherein the aramid fiber has a coating of chitosan in the amount of 1 to 10%, based on the weight of the fiber. 6. The friction paper of claim 5 wherein the friction coefficient of the paper is at least 5% greater than the friction coefficient of a similar paper without chitosan. 7. A process for making aramid pulp coated with chitosan comprising the steps of: (a) dispersing aramid fibers in a solution of chitosan in water of pH 2.5 to 4.5 at a concentration of 1 to 10% based on weight of the aramid fibers to yield a dispersion of aramid fibers; (b) changing the pH of the dispersion to pH 6.5 to 11 to cause the chitosan to precipitate and coat the dispersed aramid fibers; and (c) separating the chitosan-coated fibers from the water. 8. The process of claim 7 wherein the aramid fibers are aramid pulp. 9. The process of claim 7 wherein the chitosan is dissolved to make a chitosan solution and the aramid fibers are then dispersed in the solution. 10. The process of claim 7 wherein the aramid fibers are dispersed to make an aramid fiber dispersion and the chitosan is then dissolved in the dispersion. 11. The process of claim 7 wherein aramid fibers are aramid floc and wherein, after step (a) and before step (b), the aramid floc is refined to make aramid pulp. 12. A process for making a paper containing aramid pulp comprising the steps of: (a) establishing an aqueous paper furnish including 5 to 95% aramid fibers based on the total weight of the paper, wherein the fibers are 0.15mm to 10mm long and have a coating of 1 to 10 % by weight % chitosan based on the weight of the fibers; (b) pouring the furnish of step (a) onto a paper-making screen to remove water from the aramid fibers; and (c) drying the aramid fibers to yield a paper. 13. The process of claim 12 wherein the furnish of step (a) is established by (i) dispersing aramid fibers in a solution of chitosan in water of pH 2.5 to 4.5 at a concentration of 1 to 10% based on weight of the aramid fibers; and (ii) changing the pH of the water to 6.5 to 11. 14. The process of claim 12 wherein, after step (a) and before step (b), the pH of the furnish is changed to 6.5 to 11. |
