Cellulose derivatives

Abstract

Stable microdispersed polyanhydroglucuronic acid and salts thereof contain in their polymeric chain from 8 to 30 percent by weight of carboxyl groups, at least 80 percent by weight of these groups being of the uronic type, at most 5 percent by weight of carbonyl groups including intra- and inter-molecular 2,6 and 3,6 hemiacetals, 2,4-hemialdals and C2 and C3 aldehydes. The molecular mass of the polymeric chain is from 1x10<SUP>3 </SUP>to 3x10<SUP>5 </SUP>Daltons. The microdispersed products are prepared by subjecting a polyanhydroglucuronic acid-containing material to partial or complete hydrolysis and neutralization in an oxidative environment.

1 . A method for preparing a product comprising polyanhydroglucuronic acid and/or salts thereof wherein a polyanhydroglucuronic acid-containing material obtained by oxidation with nitrogen oxides is subjected to partial or complete hydrolysis and neutralisation in an aqueous solution of inorganic and/or organic salts and/or bases in the presence of suitable oxidising agents, the hydrolysate undergoing fractional coagulation to form a stable microdispersed product.  
     
     
         2 . A method as claimed in  claim 1  wherein the inorganic and/or organic salts and/or bases used for hydrolysis are chlorides, sulphates, carbonates, formates or acetates of alkali and/or alkaline earth metals, hydroxides of alkali and/or alkaline earth metals, alkylamines, or alkanolamines, in concentrations ranging from 1 to 10 −3  to 5 mol/l.  
     
     
         3 . A method as claimed in  claim 1  wherein the oxidative environment during hydrolysis is established by the presence of oxidising agents selected from one or more of hydrogen, sodium or magnesium peroxide, peroxoacids and their salts, hypochlorites and chlorites.  
     
     
         4 . A method as claimed in  claim 1  wherein the hydrolysate undergoes fractional coagulation by a suitable water-miscible organic solvent.  
     
     
         5 . A method as claimed in  claim 4  wherein the coagulated product is washed, or dehydrated, using a suitable water-miscible organic solvent, and/or converted, in an appropriate manner, for intended subsequent use.  
     
     
         6 . A method as claimed in  claim 1  wherein the procedure is carried out at a pH of from 1 to 12.  
     
     
         7 . A method as claimed in  claim 1  wherein the procedure is carried out at a temperature of from 0 to 100° C.  
     
     
         8 . A method as claimed in  claim 1  wherein the polyanhydroglucuronic acid-containing material is obtained by oxidation of a suitable polysaccharide, such as native or regenerated cellulose or starch.  
     
     
         9 . Stable microdispersed polyanhydroglucuronic acid and salts thereof wherever prepared by a method as claimed in  claim 1 .  
     
     
         10 . Stable microdispersed polyanhydroglucuronic acid and salts thereof containing in their polymeric chain from 8 to 30 per cent by weight of carboxyl groups, at least 80 per cent by weight of these groups being of the uronic type, at most 5 per cent by weight of carbonyl groups, and at most 0.5 per cent by weight of bound nitrogen.  
     
     
         11 . Polyanhydroglucuronic acid and salts thereof as claimed in  claim 10  containing in their polymeric chain at most 0.2 per cent by weight of bound nitrogen.  
     
     
         12 . Polyanhydroglucuronic acid and salts thereof as claimed in  claim 10  wherein the molecular mass of the polymeric chain is from 1×10 3  to 3×10 5  Daltons.  
     
     
         13 . Polyanhydroglucuronic acid and salts thereof according to  claim 12  wherein the molecular mass of the polymeric chain ranges from 5×10 3  to 1.5×10 5  Daltons.  
     
     
         14 . Polyanhydroglucuronic acid and salts thereof as claimed in  claim 10  wherein the content of carboxyl groups is in the range of from 12 to 26 per cent by weight, at least 95 per cent of these groups being of the uronic type.  
     
     
         15 . Polyanhydroglucuronic acid and salts thereof as claimed in  claim 10  containing at most 1 per cent by weight of carbonyl groups.  
     
     
         16 . Polyanhydroglucuronic acid and salts thereof according to  claim 10  wherein the carbonyl groups are intra- and intermolecular 2,6 and 3,6 hemiacetals, 2,4-hemialdals and C2-C3 aldehydes.  
     
     
         17 . Stable microdispersed polyanhydroglucuronic acid and salts thereof according to  claim 10  made up of particles sized from 0.1 to 1000 μm.  
     
     
         18 . Stable microdispersed polyanhydroglucuronic acid and salts thereof according to  claim 10  made up of fibres of from 5 to 30 μm in diameter and up to 30 mm length.  
     
     
         19 . A pharmaceutical or cosmetic composition incorporating stable microdispersed polyanhydroglucuronic acid and salts thereof as claimed in  claim 10 .  
     
     
         20 . A composition as claimed in  claim 19  in the form of a haemostatically active aerosol composition.