Apparatus and process for the surface treatment of carbon fibers

Abstract

A method for surface treating a carbon-containing material in which carbon-containing material is reacted with decomposing ozone in a reactor (e.g., a hollow tube reactor), wherein a concentration of ozone is maintained throughout the reactor by appropriate selection of at least processing temperature, gas stream flow rate, reactor dimensions, ozone concentration entering the reactor, and position of one or more ozone inlets (ports) in the reactor, wherein the method produces a surface-oxidized carbon or carbon-containing material, preferably having a surface atomic oxygen content of at least 15%. The resulting surface-oxidized carbon material and solid composites made therefrom are also described.

What is claimed is: 
     
         1 . A carbon material having a surface atomic oxygen content of at least 15%. 
     
     
         2 . The carbon material of  claim 1 , wherein said surface atomic oxygen content is at least 20%. 
     
     
         3 . The carbon material of  claim 1 , wherein said surface atomic oxygen content is at least 22%. 
     
     
         4 . The carbon material of  claim 1 , wherein said surface atomic oxygen content is at least 25%. 
     
     
         5 . The carbon material of  claim 1 , wherein said surface atomic oxygen content is up to 30%. 
     
     
         6 . The carbon material of  claim 1 , wherein said surface atomic oxygen content is up to 25%. 
     
     
         7 . The carbon material of  claim 1 , wherein said carbon material is coated with a sizing agent. 
     
     
         8 . The carbon material of  claim 7 , wherein said sizing agent is an epoxy sizing agent. 
     
     
         9 . The carbon material of  claim 1 , wherein said carbon material is selected from carbon fiber, carbon whisker, carbon fiber tow, a woven or non-woven mat of carbon fiber, carbon block, carbon film, and carbon particles. 
     
     
         10 . The carbon material of  claim 1 , wherein said surface atomic oxygen content is provided predominantly by the presence of hydroxy and carboxy surface groups. 
     
     
         11 . A solid composite comprised of carbon material embedded within a polymeric matrix, wherein said carbon material has a surface atomic oxygen content of at least 15%. 
     
     
         12 . The solid composite of  claim 11 , wherein said surface atomic oxygen content is at least 20%. 
     
     
         13 . The solid composite of  claim 11 , wherein said surface atomic oxygen content is at least 22%. 
     
     
         14 . The solid composite of  claim 11 , wherein said surface atomic oxygen content is at least 25%. 
     
     
         15 . The solid composite of  claim 11 , wherein said surface atomic oxygen content is up to 30%. 
     
     
         16 . The solid composite of  claim 11 , wherein said surface atomic oxygen content is up to 25%. 
     
     
         17 . The solid composite of  claim 11 , wherein said carbon material is coated with a sizing agent. 
     
     
         18 . The solid composite of  claim 17 , wherein said sizing agent is an epoxy sizing agent. 
     
     
         19 . The solid composite of  claim 11 , wherein said polymeric matrix is a thermoset. 
     
     
         20 . The solid composite of  claim 19 , wherein said thermoset is derived from vinyl-addition polymerization of an unsaturated resin containing carbon-carbon double bonds. 
     
     
         21 . The solid composite of  claim 20 , wherein said unsaturated resin is a vinyl ester resin. 
     
     
         22 . The solid composite of  claim 20 , wherein said unsaturated resin is an unsaturated polyester resin. 
     
     
         23 . The solid composite of  claim 11 , wherein said polymeric matrix is derived from an acrylate or methacrylate resin. 
     
     
         24 . The solid composite of  claim 20 , wherein said unsaturated resin is in admixture with at least one unsaturated reactive diluent that is cured with the unsaturated resin. 
     
     
         25 . The solid composite of  claim 24 , wherein said unsaturated reactive diluent is comprised of one or more compounds selected from the group consisting of styrene, divinylbenzenes, methacrylates, acrylates, and vinyl esters. 
     
     
         26 . The solid composite of  claim 11 , wherein said polymeric matrix is a thermoplastic. 
     
     
         27 . A method for surface treating a carbon-containing material, the method comprising reacting said carbon-containing material with decomposing ozone by passing said carbon-containing material through a hollow tube containing a flowing gas stream comprised of ozone under conditions where said ozone decomposes after being introduced into said hollow tube by at least one ozone inlet, wherein a concentration of said ozone is maintained throughout said hollow tube by appropriate selection of at least processing temperature, gas stream flow rate, tube diameter, tube length, ozone concentration entering said hollow tube, and position of said ozone inlet in said hollow tube; wherein said method produces a surface-oxidized carbon-containing material. 
     
     
         28 . The method of  claim 27 , wherein said carbon-containing material is selected from carbon fiber, carbon whisker, carbon fiber tow, a woven or non-woven mat of carbon fiber, carbon block, carbon film, and carbon particles. 
     
     
         29 . The method of  claim 27 , wherein said ozone is maintained within a concentration of at least 40% throughout said tube relative to the concentration of ozone entering at said ozone inlet. 
     
     
         30 . The method of  claim 27 , wherein said hollow tube has at least an interior portion that is non-metallic. 
     
     
         31 . The method of  claim 30 , wherein at least said interior portion is ceramic or glass. 
     
     
         32 . The method of  claim 27 , wherein said hollow tube has a diameter of at least three inches. 
     
     
         33 . The method of  claim 27 , wherein said processing temperature is at least 40° C. and up to 200° C. 
     
     
         34 . The method of  claim 27 , wherein said processing temperature is at least 50° C. and less than 200° C. 
     
     
         35 . The method of  claim 27 , wherein said processing temperature is at least 50° C. and up to 190° C. 
     
     
         36 . The method of  claim 27 , wherein said processing temperature is at least 75° C. and up to 190° C. 
     
     
         37 . The method of  claim 27 , wherein said processing temperature is at least 100° C. and up to 180° C. 
     
     
         38 . The method of  claim 27 , wherein said processing temperature is at least 120° C. and up to 180° C. 
     
     
         39 . The method of  claim 27 , wherein said processing temperature is at least 140° C. and up to 180° C. 
     
     
         40 . The method of  claim 27 , further comprising a pretreatment step of said carbon-containing material wherein said carbon-containing material is contacted with a solution of an oxidant prior to said surface treatment with ozone. 
     
     
         41 . The method of  claim 40 , wherein said oxidant is comprised of a peroxide. 
     
     
         42 . The method of  claim 41 , wherein said peroxide is in a concentration in said solution of 0.1 wt % to 60 wt %. 
     
     
         43 . The method of  claim 40 , wherein said oxidant is comprised of a mineral or organic acid. 
     
     
         44 . The method of  claim 27 , wherein said method is a continuous process in which said carbon-containing material is continuously processed by passing said carbon-containing material through the length of said hollow tube during said method. 
     
     
         45 . The method of  claim 27 , wherein said method is a continuous process in which said carbon-containing material is in the form of a tow of carbon fiber that is continuously processed by passing said tow through the length of said hollow tube during said method. 
     
     
         46 . The method of  claim 45 , wherein said tow is held in a creel, from which the tow is pulled and fed into said hollow tube to be continuously processed. 
     
     
         47 . The method of  claim 27 , wherein said ozone concentration entering said hollow tube is in a concentration of 0.1 to 12 wt % in a carrier gas. 
     
     
         48 . The method of  claim 27 , wherein said carbon-containing material is contacted with said gas stream comprised of decomposing ozone for 1 second to 30 minutes. 
     
     
         49 . The method of  claim 27 , further comprising coating the surface-oxidized carbon-containing material with a sizing agent. 
     
     
         50 . The method of  claim 49 , wherein said sizing agent is an epoxy sizing agent. 
     
     
         51 . The method of  claim 27 , wherein the method produces a carbon fiber with a reduced diameter. 
     
     
         52 . The method of  claim 27 , wherein said carbon-containing material has an elastic modulus of at least 50 Mpsi. 
     
     
         53 . A method for surface treating a carbon-containing material, the method comprising reacting said carbon-containing material with decomposing ozone in a reactor containing a flowing gas stream comprised of ozone under conditions where said ozone decomposes after being introduced into said reactor by at least one ozone inlet, wherein a concentration of said ozone is maintained throughout said reactor by appropriate selection of at least processing temperature, gas stream flow rate, reactor dimensions, ozone concentration entering said reactor, and position of said ozone inlet in said reactor; wherein said method produces a surface-oxidized carbon-containing material. 
     
     
         54 . A carbon material having an oxidized surface wherein surface carboxyl and hydroxyl groups are present in said oxidized surface in an amount of at least 70% with respect to total number of oxygen-containing surface functional groups in said oxidized surface.