Fiber composite

Abstract

To provide a cellulose fiber composite having high transparency, low water absorption and low coefficient of linear thermal expansion. A fiber composite which comprises fibers having an average fiber diameter of at most 30 nm and a matrix material and which has a haze of at most 5 according to JIS K-7136 when the fiber composite has a thickness of 100 μm.

1 - 11 . (canceled) 
     
     
         12 . A microfibrillated cellulose fiber dispersion which is a dispersion of fibers comprising cellulose having cellulose type I crystal and having repeating units represented by formula (1) and/or its derivative: 
       
         
           
           
               
               
           
         
         wherein each of X 1 , X 2 , and X 3 , independent of one another, is a hydrogen atom, a C 1-20  alkylcarbonyl group, a C 2-6  alkenylcarbonyl group which may be substituted by an allyl group, an alkynylcarbonyl group, an arylcarbonyl group, a nicotinoyl group, an isonicotinoyl group, or a furoyl group, and 
         wherein, when an acceleration of 38,900 G is exerted for 30 minutes by a centrifugal separator to such a dispersion adjusted so that its viscosity at a shear rate of 10 s −1  as measured at 25° C. becomes at most 100 mPa·s, the concentration of the microfibrillated cellulose and/or its derivative in a 10% supernatant in the entire volume, is at least 50% of the concentration of the cellulose and/or its derivative in the dispersion before the dispersion is subjected to the centrifugal separator. 
       
     
     
         13 . A cellulose fiber planar structure which is produced from the microfibrillated cellulose fiber dispersion as defined in  claim 12  and which has a haze of at most 50 in a thickness of 50 μm. 
     
     
         14 . A cellulose fiber planar structure produced from the microfibrillated cellulose fiber dispersion as defined in  claim 12  and having a porosity of at least 10 vol % and at most 90 vol % and a thickness of at least 100 nm and at most 1 cm, and when impregnated with an oil having a refractive index of 1.52 and observed by a microscope, a volume fraction of fibers having a fiber diameter of at least 400 nm is at most 10%. 
     
     
         15 . Cellulose fiber particles produced from the microfibrillated cellulose fiber dispersion as defined in  claim 12  and having a particle diameter of at least 1 μm and at most 1 mm, and when impregnated with an oil having a refractive index of 1.52 and observed by a microscope, a volume fraction of fibers having a fiber diameter of at least 400 nm is at most 10%. 
     
     
         16 . A polymer cellulose composite obtained by combining the cellulose fiber planar structure as defined in  claim 13 , with a polymer other than cellulose. 
     
     
         17 . A polymer cellulose composite obtained by laminating a layer of the cellulose fiber planar structure as defined in  claim 13 , with a planar structure layer of a polymer other than cellulose. 
     
     
         18 . A polymer cellulose composite comprising the cellulose fiber planar structure as defined in  claim 13  and a polymer other than cellulose, comprised in the cellulose fiber planar structure. 
     
     
         19 . The polymer cellulose composite according to  claim 16 , having an inorganic layer laminated thereon. 
     
     
         20 . A structural material comprising the polymer cellulose composite as defined in  claim 16 . 
     
     
         21 . A substrate comprising the polymer cellulose composite as defined in  claim 16 . 
     
     
         22 . A window material comprising the polymer cellulose composite as defined in  claim 16 . 
     
     
         23 . A vehicle body comprising the polymer cellulose composite as defined in  claim 16 . 
     
     
         24 . A method for microfibrillating cellulose fibers, which comprises irradiating a dispersion of cellulose fibers obtained from a plant-derived material and having an average minimum length of at least 10 μm and an average maximum length of at most 10 cm, with ultrasonic waves having a frequency of at least 15 kHz and at most 1 MHz and an effective power density of at least 1 W/cm 2 , to obtain a dispersion of micro fibrillated cellulose fibers having an average fiber diameter of at most 100 nm. 
     
     
         25 . The method for microfibrillating cellulose fibers according to  claim 24 , further comprising microfibrillating before the irradiation with the ultrasonic waves. 
     
     
         26 . The method for microfibrillating cellulose fibers according to  claim 25 , wherein the microfibrillating is a reducing the pressure by letting a dispersion of the material jet from a high pressure atmosphere of at least 30 MPa. 
     
     
         27 . The method for microfibrillating cellulose fibers according to  claim 24 , further comprising chemically modifying the material. 
     
     
         28 . A polymer cellulose composite obtained by combining the cellulose fiber particles as defined in  claim 15 , with a polymer other than cellulose.