Surface Attachment of Particles to Cellulose Ester Fibers

Abstract

This invention pertains to the surface attachment of particles, such as metal oxides, to cellulose ester fibers. The particles are applied to the surface of the cellulose ester fibers using a protic liquid that is substantially free of plasticizer.

We claim: 
     
         1 . A method of attaching metal oxide particles to the surface of cellulose ester fibers, comprising:
 contacting cellulose ester fibers with a mixture comprising metal oxide particles dispersed in a protic liquid to attach the metal oxide particles on the surface of the fibers,   wherein the mixture is substantially free of plasticizer.   
     
     
         2 . The method according to  claim 1 , wherein the protic liquid is water, alcohol, or mixtures thereof. 
     
     
         3 . The method according to  claim 1 , wherein the metal oxide particles comprise mono-metal oxides or bi-metal oxides. 
     
     
         4 . The method according to  claim 1 , wherein the metal oxide particles are photoactive. 
     
     
         5 . The method according to  claim 4 , wherein the metal oxide particles comprise rutile titanium dioxide or anatase titanium dioxide, or mixtures of rutile titanium dioxide and anatase titanium dioxide. 
     
     
         6 . The method according to  claim 4 , wherein the metal oxide particles comprise mixed-phase titanium dioxide particles. 
     
     
         7 . The method according to  claim 6 , wherein the mixed-phase titanium dioxide particles comprise an anatase phase in an amount ranging from 50 to 98 wt % and a rutile phase in an amount ranging from 2 to 50 wt %. 
     
     
         8 . The method according to  claim 1 , wherein the metal oxide particles have a diameter of 1 nm to 50 microns. 
     
     
         9 . The method according to  claim 1 , wherein the metal oxide particles have a diameter of 1 nm to 250 nm. 
     
     
         10 . The method according to  claim 1 , wherein the metal oxide particles have a diameter of 5 nm to 50 nm. 
     
     
         11 . The method according to  claim 1 , wherein the metal oxide particles have a surface area of 1 to 400 m 2 /g. 
     
     
         12 . The method according to  claim 1 , wherein the metal oxide particles have a surface area of 10 to 350 m 2 /g. 
     
     
         13 . The method according to  claim 1 , wherein the metal oxide particles have a surface area of 10 to 150 m 2 /g. 
     
     
         14 . The method according to  claim 1 , wherein after the contacting step, the fibers comprise from 0.01 to 10 wt % of the metal oxide particles. 
     
     
         15 . The method according to  claim 1 , wherein the cellulose ester fibers comprise cellulose acetate fibers, cellulose propionate fibers, cellulose butyrate fibers, cellulose acetate propionate fibers, or cellulose acetate butyrate fibers. 
     
     
         16 . The method according to  claim 1 , which further comprises:
 dispersing the metal oxide particles in the protic liquid to form the mixture;   removing at least a portion of the protic liquid from the surface of the fibers after contacting the fibers with the mixture;   removing at least a portion of excess or unattached metal oxide particles from the surface of the fibers; and   drying the fibers to obtain finished cellulose ester fibers with attached metal oxide particles.   
     
     
         17 . Cellulose ester fibers produced according to the method of  claim 1 . 
     
     
         18 . Cellulose ester fibers produced according to the method of  claim 16 . 
     
     
         19 . The cellulose ester fibers according to  claim 16 , which are substantially free of plasticizer. 
     
     
         20 . A cigarette filter which comprises the cellulose ester fibers according to  claim 16 .