Highly Heat-Resistant Resin Composite Including Chemically Modified, Fine Cellulose Fibers

Abstract

Provided is a resin composite having high mechanical properties which make the resin composite moldable into and usable as members for use in applications such as vehicle-mounted members and electrical materials. The resin composite comprises 0.5-40 mass % chemically modified, fine cellulose fibers and a resin, wherein the chemically modified, fine cellulose fibers have a pyrolysis initiation temperature (T D ) of 270° C. or higher, a number-average fiber diameter of 10 nm or larger but less than 1 μm, and a degree of crystallinity of 60% or higher. In a preferred embodiment, the chemically modified, fine cellulose fibers have a coefficient of variation (CV) in DS unevenness ratio, DSs/DSt, of 50% or less, the DS unevenness ratio being the ratio of the modification degree (DSs) of the surface layers of the fibers to the modification degree (DSt) of the whole of the fibers.

1 - 33 . (canceled) 
     
     
         34 . Chemically modified fine cellulose fibers wherein the weight-average molecular weight (Mw) is 100,000 or higher, the ratio (Mw/Mn) of the weight-average molecular weight (Mw) and number-average molecular weight (Mn) is 6 or lower, the alkali-soluble portion content is 12 mass % or lower and the degree of crystallinity is 60% or higher. 
     
     
         35 . The chemically modified fine cellulose fibers according to  claim 34 , wherein the thermal decomposition initiation temperature (T D ) is 270° C. or higher and the number-average fiber diameter is 10 nm or greater and less than 1 μm. 
     
     
         36 . The chemically modified fine cellulose fibers according to  claim 34 , which are esterified fine cellulose fibers. 
     
     
         37 . The chemically modified fine cellulose fibers according to  claim 34 , wherein the average degree of substitution of hydroxyl groups is 0.5 or greater. 
     
     
         38 . The chemically modified fine cellulose fibers according to  claim 34 , wherein the coefficient of variation (CV) of the DS non-uniformity ratio (DSs/DSt), as the ratio of the degree of modification (DSs) of the fiber surface with respect to the degree of modification (DSt) of the entire chemically modified fine cellulose fibers, is 50% or lower. 
     
     
         39 . The chemically modified fine cellulose fibers according to  claim 34 , wherein the average content of the acid-insoluble component per unit specific surface area of the chemically modified fine cellulose fibers is 1.0 mass %·g/m 2  or lower. 
     
     
         40 . A method for producing chemically modified fine cellulose fibers, which includes:
 defibrating a cellulose starting material having a weight-average molecular weight (Mw) of 100,000 or greater, a ratio (Mw/Mn) of weight-average molecular weight (Mw) and number-average molecular weight (Mn) of 6 or lower and an alkali-soluble content of 12 mass % or lower, in a dispersion that includes an aprotic solvent, to obtain fine cellulose fibers, and   adding a modifying agent-containing solution to the dispersion to modify the fine cellulose fibers, thereby obtaining chemically modified fine cellulose fibers having a weight-average molecular weight (Mw) of 100,000 or greater, a ratio (Mw/Mn) of weight-average molecular weight (Mw) and number-average molecular weight (Mn) of 6 or lower, an alkali-soluble content of 12 mass % or lower and a degree of crystallinity of 60% or higher.   
     
     
         41 . A resin composite containing 0.5 to 40 mass % of chemically modified fine cellulose fibers and a resin,
 wherein the DS non-uniformity ratio (DSs/DSt), as the ratio of the degree of modification (DSs) of the fiber surfaces with respect to the degree of modification (DSt) of the entire chemically modified fine cellulose fibers, is 1.1 or greater, and the coefficient of variation (CV) of the DS non-uniformity ratio (DSs/DSt) is 50% or lower.   
     
     
         42 . The resin composite according to  claim 41 , wherein the chemically modified fine cellulose fibers have:
 a thermal decomposition initiation temperature (T D ) of 270° C. or higher,   a number-average fiber diameter of 10 nm or greater and less than 1 μm, and   a degree of crystallinity of 60% or higher.   
     
     
         43 . The resin composite according to  claim 41 , wherein the resin is a thermoplastic resin. 
     
     
         44 . The resin composite according to  claim 41 , wherein the melting point of the resin is 220° C. or higher. 
     
     
         45 . The resin composite according to  claim 41 , wherein the weight-average molecular weight (Mw) of the chemically modified fine cellulose fibers is 100,000 or greater, and the ratio (Mw/Mn) of the weight-average molecular weight (Mw) and number-average molecular weight (Mn) is 6 or lower. 
     
     
         46 . The resin composite according to  claim 41 , wherein the average degree of substitution of hydroxyl groups of the chemically modified fine cellulose fibers is 0.5 or greater. 
     
     
         47 . The resin composite according to  claim 41 , wherein the chemically modified fine cellulose fibers are esterified fine cellulose fibers. 
     
     
         48 . The resin composite according to  claim 41 , wherein the content of the alkali-soluble portion of the chemically modified fine cellulose fibers is 12 mass % or lower. 
     
     
         49 . The resin composite according to  claim 41 , wherein the average content of the acid-insoluble component per unit specific surface area of the chemically modified fine cellulose fibers is 1.0 mass %·g/m 2  or lower. 
     
     
         50 . A resin composite containing 0.5 to 40 mass % of chemically modified fine cellulose fibers according to  claim 34 , and a resin. 
     
     
         51 . A method for producing a resin composite containing 0.5 to 40 mass % of chemically modified fine cellulose fibers, and a resin, wherein the method includes:
 a defibrating step in which a cellulose starting material is defibrated in a dispersion that includes the cellulose starting material and an aprotic solvent but essentially does not include an ionic liquid or sulfuric acid, to obtain fine cellulose fibers,   a modifying step in which a solution that includes a modifying agent is added to the dispersion for chemical modification of the fine cellulose fibers, to obtain chemically modified fine cellulose fibers, and   a kneading step in which the chemically modified fine cellulose fibers and the resin are kneaded,   the DS non-uniformity ratio (DSs/DSt), as the ratio of the degree of modification (DSs) of the fiber surfaces with respect to the degree of modification (DSt) of the entire chemically modified fine cellulose fibers, is 1.1 or greater, and the coefficient of variation (CV) of the DS non-uniformity ratio (DSs/DSt) is 50% or lower.   
     
     
         52 . A method for producing a resin composite according to  claim 41 , wherein the method includes:
 a step of defibrating cellulose in a dispersion containing a cellulose starting material with a cellulose purity of 85 mass % or greater, and an aprotic solvent, to obtain fine cellulose fibers,   a step of adding a solution containing a modifying agent to the dispersion to modify the fine cellulose fibers, thereby obtaining chemically modified fine cellulose fibers having a thermal decomposition initiation temperature (T D ) of 270° C. or higher, a number-average fiber diameter of 10 nm or greater and less than 1 μm, and a degree of crystallinity of 60% or higher, and   a step of mixing the chemically modified fine cellulose fibers with a resin.   
     
     
         53 . The method according to  claim 51 , wherein the aprotic solvent is dimethyl sulfoxide, and the modifying agent is vinyl acetate or acetic anhydride. 
     
     
         54 . The method according to  claim 52 , wherein the aprotic solvent is dimethyl sulfoxide, and the modifying agent is vinyl acetate or acetic anhydride. 
     
     
         55 . A member for an automobile, comprising a resin composite according to  claim 41 . 
     
     
         56 . A member for an automobile, comprising a resin composite according to  claim 50 . 
     
     
         57 . A member for an electronic product, comprising a resin composite according to  claim 41 . 
     
     
         58 . A member for an electronic product, comprising a resin composite according to  claim 50 .