CONTEXT

Native cellulose occurs in the form of microcrystals and/or of very elongated microfibrils, often organized as fibres. This cellulose can be found in plants, but also in certain fungi, bacteria, amoebae and even some marine animals.

Acid hydrolysis of cellulose in an aqueous medium leads to stable aqueous colloidal suspensions of individual microcrystals. Depending on the origin of the cellulose, the lateral dimensions of the microcrystals and/or microfibrils can vary from 2 nm to 50 nm. The lengths of the said microcrystals and/or microfibrils can greatly exceed one micron. Depending on the origin of the cellulose (for example cotton) and the concentrations used (for example high concentrations, varying between 2 and 10% w/w), stable colloidal dispersions of cellulose in water are organized in the form of a liquid crystal of the cholesteric type  the spacing of which can vary from 80 to 10 mu m, depending on the operating conditions employed. All properties and applications of cellulose microcrystals and/or microfibrils are due to the very high form factor of these objects (i.e. the ratio of length to width is high, typically over 10), and to their good dispersion in the usage medium. However, until now it has only been possible to obtain dispersions of cellulose microfibrils and/or microcrystals in water or in very polar solvents (glycerol, ethylene glycol, DMSO etc.)

TECHNICAL DESCRIPTION

The present invention supplies suspensions or dispersions of microfibrils and/or of microcrystals, especially of cellulose or of any other fibrillar organic substance selected from the group consisting of cellulose, chitin, and polysaccharides, in the organic solvents for which the said suspensions or dispersions had until now been impossible to produce providing thus stable suspensions or dispersions of cellulose microfibrils and/or microcrystals in organic solvents, especially apolar or slightly polar ones, without chemical modification of the cellulose.  Said colloidal dispersion contains in addition, at least one compound possessing a hydrophilic part and a hydrophobic part.

BENEFITS

No chemical modification of the fibrils.  Furthermore these aqueous dispersions or suspensions of microcrystals and/or microfibrils, especially of cellulose, which once they have been dried can be redispersed in water or in an organic solvent, while preserving their properties connected with dispersion.

INDUSTRIAL APPLICATIONS

* Manufacture of composites: most of the synthetic polymers are only soluble in organic solvents; thus, the application of cellulose microcrystals and/or microfibrils is limited to latex  or to water-soluble resins , and for example to cellulose acetate in the case of surface-modified microcrystals.

* Thickener: just as in the case of composites, applications as thickener are limited to aqueous media; thus, we may mention the use of cellulose microfibrils and/or microcrystals for the production of oil-field drilling fluid (drilling muds) , or for improving processed foodstuffs .

* Production of  paper with variable optical properties.

* Preparation of cosmetic or dermatological compositions, for the manufacture of descaling formulations.

* pharmacy, personal hygiene products

For further information, please contact us (Ref 84236-01)