Supplementation of cellulose nanofibrils with carboxycellulose which has a low degree of substitution

Abstract

The invention concerns compositions containing essentially amorphous cellulose nanofibrils, carboxyl cellulose with a degree of substitution not more than o.95 as additive, and optionally at least one co-additive, the content in additive and optional co-additive being less than 30 wt. % relative to the weight of nanofibrils and additive and optional co-additive. The invention also concerns a method for preparing such compositions, consistin in adding to a substantially amorphous nanofibril suspension, the additive and optionally the co-additive(s), then in drying the suspension thus additivated. The resulting compositions are easily redispersable and preserve all their rheological properties.

1 . Composition comprising cellulose nanofibrils with a degree of crystallinity of less than or equal to 50%, carboxycellulose with a degree of substitution of less than or equal to 0.95 as additive, and optionally at least one co-additive, the content of additive and of optional co-additive being less than or equal to 30% by weight relative to the weight of nanofibrils and of additive and of optional co-additive.  
     
     
         2 . Compositon according to the preceding claim, characterized in that the nanofibrils have a degree of crystallinity of between 15% and 50%.  
     
     
         3 . Composition according to either of claims  1  and 2, characterized in that the additive is carboxymethylcellulose.  
     
     
         4 . Composition according to any one of the preceding claims, characterized in that the cellulose nanofibrils are obtained from cells consisting of at least 80% primary walls.  
     
     
         5 . Composition according to the preceding claim, characterized in that the cellulose nanofibrils are charged with acids and with acidic polysaccharides, alone or as a mixture.  
     
     
         6 . Composition according to any one of the preceding claims, characterized in that it comprises at least one co-additive chosen from: 
 saccharide monomers or oligomers,    compounds of formula (R 1 R 2 N)COA, in which formula R 1  and R 2 , which may be identical or different, represent hydrogen or a C 1 -C 10 , preferably C 1 -C 5 , alkyl radical, A represents hydrogen, a C 1 -C 10 , preferably C 1 -C 5 , alkyl radical or alternatively the group R′ 1 R′ 2 N with R 1  and R′ 2 , which may be identical or different, representing hydrogen or a C 1 -C 10 , preferably C 1 -C 5 , alkyl radical,    cationic or amphoteric surfactants, it being possible for these co-additives to be used alone or as a mixture.    
     
     
         7 . Composition according to any one of the preceding claims, characterized in that the co-additive content is less than 30% by weight relative to the weight of nanofibrils and of additive and of co-additive.  
     
     
         8 . Composition according to any one of the preceding claims, characterized in that the co-additive is chosen from saccharide monomers or oligomers or compounds of formula (R 1 R 2 N)COA with a content of between 1 and 25% by weight relative to the weight of nanofibrils and of additive and of co-additive.  
     
     
         9 . Composition according to any one of the preceding claims, characterized in that the co-additive is chosen from cationic and amphoteric surfactants with a content of between 1 and 10% by weight relative to the weight of nanofibrils and of additive and of co-additive.  
     
     
         10 . Composition according to any one of the preceding claims, characterized in that the content of additive and of co-additive is between 5 and 30% by weight relative to the weight of nanofibrils and of additive and of co-additive.  
     
     
         11 . Composition according to any one of the preceding claims, characterized in that the solids content is at least 40% by weight.  
     
     
         12 . Process for preparing a composition according to any one of the preceding claims, in which cellulose nanofibrils are prepared from cellulosic pulp which makes it possible to obtain cellulose nanofibrils with a degree of crystallinity of less than or equal to 50%, by carrying out at least one extraction, optionally at least one step of bleaching of the pulp thus treated, after which the resulting pulp is separated out, and a homogenization step is carried out in at least one cycle, characterized in that the following steps are carried out: 
 at least some of the additive and optionally co-additive(s) is added to the nanofibril suspension which has optionally undergone at least one homogenization cycle,    a step of drying the suspension thus supplemented is carried out.    
     
     
         13 . Preparation process according to the preceding claim, in which cellulose nanofibrils are prepared from cellulosic pulp comprising cells consisting of at least about 80% primary walls.  
     
     
         14 . Preparation process according to either of claims  12  and  13 , characterized in that at least some of the additive and optionally co-additive(s) is added to the suspension after the homogenization step, after this suspension has undergone at least one concentration step.  
     
     
         15 . Preparation process according to    claim 13   , characterized in that at least some of the additive and optionally co-additive(s) is added to the suspension after the homogenization step, before the said suspension has undergone a concentration step.  
     
     
         16 . Preparation process according to either of claims  14  or  15 , characterized in that the concentration step is carried out in order to obtain a suspension with solids content of not more than about 35% by weight.  
     
     
         17 . Preparation process according to    claim 13   , characterized in that at least some of the additive and optionally co-additive(s) is added to the suspension before or during the homogenization step.  
     
     
         18 . Preparation process according to any one of    claims 12    to    17   , characterized in that the cellulose nanofibril suspension is shaped prior to drying.  
     
     
         19 . Preparation process according to any one of    claims 12    to    18   , characterized in that the drying step is carried out so as to maintain not less than 5% by weight of water relative to the weight of cellulose nanofibrils.  
     
     
         20 . Preparation process according to the preceding claim, characterized in that a blending step is carried out after the drying.  
     
     
         21 . Aqueous suspension comprising cellulose nanofibrils, characterized in that it is obtained by dispersing the composition according to any one of    claims 1    to    11    or obtained according to any one    claims 12    to    20   .  
     
     
         22 . Suspension according to the preceding claim, characterized in that it has a Theological profile of shear-thinning type.  
     
     
         23 . Suspension according to either of claims  21  or  22 , characterized in that it has a level of viscosity corresponding to at least 50%, for a shear rate of at least 1 s -1 , of the level of viscosity of a cellulose nanofibril suspension which has not undergone a drying step and which does not comprise an additive or co-additives.  
     
     
         24 . Use of carboxycellulose, and optionally of co-additives, with cellulose nanofibrils which have a degree of crystallinity of less than or equal to 50%, for the purpose of conserving a shear-thinning Theological profile for a suspension comprising cellulose nanofibrils with a degree of crystallinity of less than or equal to 50% which have undergone a drying step.  
     
     
         25 . Use of the compositions according to any one of    claims 1    to    11   , as well as of the suspensions according to any one of    claims 21    to    24   , as additives in formulations intended for the cosmetics and/or detergency sector.  
     
     
         26 . Use of the compositions according to any one of    claims 1    to    11   , as well as of the suspensions according to any one of    claims 21    to    24   , as additives in food formulations.  
     
     
         27 . Use of the compositions according to any one of    claims 1    to    11   , as well as of the suspensions according to any one of    claims 21    to    24   , as additives in formulations for public works and construction.