Novel lignin derivatives, molded products using the same and processes for making the same

Abstract

The present invention provides a process for producing novel lignin derivatives, which comprises using a lignophenol derivative containing a diphenylpropane unit formed by binding a carbon atom at an ortho-position relative to a phenolic hydroxyl group of a phenol derivative to a carbon atom at a benzyl-position of a phenylpropane fundamental unit of lignin, and binding an oxygen atom of the hydroxyl group and a β-positional carbon atom under alkali conditions under which the hydroxyl group can dissociate, to obtain an arylcoumaran derivative containing an arylcoumaran unit in which a coumaran skeleton is bound to an aromatic ring of lignin.

1 . A method of making a cross-linking material comprising:
 (a) solvating lignin in ligno-cellulose material with phenol and/or a phenol derivative having at least one unsubstituted ortho-position or para-position with respect to a hydroxyl group of a phenol group,   (b) contacting the solvated lignin with concentrated acid, thereby forming a carbon-carbon bond between the at least one unsubstituted ortho-position or para-position of the phenol or the phenol derivative and a benzyl position of a phenylpropane unit of the lignin and forming cleavages of benzyl-aryl ether bonds, whereby a lignophenol derivative having a plurality of diphenylpropane units is formed, and   (c) contacting the lignophenol derivative with at least one cross-linking compound selected from an aldehyde and a diisocyanate under alkaline conditions that will dissociate the phenolic hydroxyl group, thereby forming a cross-linking lignin-based polymer by introducing a cross-linking functional group at the ortho-position, the para-position or both the ortho-position and para-position with respect to the phenolic hydroxyl group of the diphenylpropane unit.   
     
     
         2 . A method as in  claim 1 , wherein the lignophenol derivative has an UV adsorption maximum at about 280 nm, an ionization differential maximum at about 300 nm and a shoulder peak at a longer wavelength not observed in a UV spectrum. 
     
     
         3 . A method as in  claim 1 , wherein the lignophenol derivative is substantially soluble in methanol, ethanol, acetone, dioxane, tetrahydrofuran, pyridine and dimethylformamide. 
     
     
         4 . A method as in  claim 1 , wherein the lignophenol derivative has substantially no benzyl hydroxyl groups at a side chain (α) position of the diphenylpropane unit. 
     
     
         5 . A method as in  claim 1 , wherein under said alkaline conditions, β-aryl ether bonds are cleaved between diphenylpropane units within the cross-linking based polymer. 
     
     
         6 . A method as in  claim 1 , wherein step (c) is performed at about 40-80° C. 
     
     
         7 . A method as in  claim 1 , wherein the cross-linking compound is formaldehyde. 
     
     
         8 . A method as in  claim 1 , wherein the phenol derivative is m-cresol or p-cresol. 
     
     
         9 . A method as in  claim 1 , wherein the phenol derivative is 2,4-xylenol or 2,6-xylenol. 
     
     
         10 . A method as in  claim 1 , further comprising mixing a molding substrate material with the cross-linking lignin-based polymer, wherein the cross-linking lignin-based polymer acts as a binder for the molding substrate material. 
     
     
         11 . A method as in  claim 10 , further comprising heating the mixture of the molding substrate material and the cross-linking lignin-based polymer in order to induce cross-linking functional groups to cross-link. 
     
     
         12 . A method as in  claim 1 , wherein the lignophenol derivative: (a) has an UV adsorption maximum at about 280 nm, an ionization differential maximum at about 300 nm and a shoulder peak at a longer wavelength not observed in a UV spectrum, (b) is substantially soluble in methanol, ethanol, acetone, dioxane, tetrahydrofuran, pyridine and dimethylforamide, and (c) has substantially no benzyl hydroxyl groups at a side chain (α) position of the diphenylpropane unit. 
     
     
         13 . A method as in  claim 12 , wherein the cross-linking compound is formaldehyde. 
     
     
         14 . A method as in  claim 13 , wherein the phenol derivative is m-cresol or p-cresol. 
     
     
         15 . A method as in  claim 13 , wherein the phenol derivative is 2,4-xylenol or 2,6-xylenol. 
     
     
         16 . A method as in  claim 15 , further comprising mixing a molding substrate material with the cross-linking lignin-based polymer, wherein the cross-linking lignin-based polymer acts as a binder for the molding substrate material. 
     
     
         17 . A method as in  claim 16 , further comprising heating the mixture of the molding substrate material and the cross-linking lignin-based polymer in order to cross-link the cross-linking functional groups. 
     
     
         18 . A method as in  claim 14 , further comprising mixing a molding substrate material with the cross-linking lignin-based polymer, wherein the cross-linking lignin-based polymer acts as a binder for the molding substrate material. 
     
     
         19 . A method as in  claim 18 , further comprising heating the mixture of the molding substrate material and the cross-linking lignin-based polymer in order to induce cross-linking functional groups to cross-link. 
     
     
         20 . A cross-linking lignin based polymer formed by the method of  claim 1 . 
     
     
         21 . A cross-linking lignin based polymer formed by the method of  claim 7 . 
     
     
         22 . A cross-linking lignin based polymer formed by the method of  claim 8 . 
     
     
         23 . A cross-linking lignin based polymer formed by the method of  claim 9 . 
     
     
         24 . A cross-linking lignin based polymer formed by the method of  claim 12 .