Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2001-06-25
2004-03-09
Barts, Samuel (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S084000, C536S095000, C536S096000, C536S124000
Reexamination Certificate
active
06703497
ABSTRACT:
A subject-matter of the present invention is cellulose microfibrils with a modified surface, their process of preparation and their use.
Another subject-matter of the invention is compositions comprising cellulose microfibrils with a modified surface.
Generally, native cellulose is a chain of D-anhydroglucopyranose units bonded to one another at the &bgr;-1,4 positions. The degree of polymerization (DP) of the said chain can vary from a few hundred to several thousand monomer units, depending upon the source used. In the native state, intermolecular hydrogen bonds promote a parallel association of the cellulose chains with one another to form microfibrils with more or less crystalline structures, the diameter of which can vary from 10 Å to 500 Å.
These microfibrils are well known materials which have already been proposed, in general, for modifying the rheology of the media into which they are introduced.
In the case of fluid aqueous or organic media of the type of those intended for the production in particular of cosmetic compositions, of drilling fluids, and the like, the microfibrils can modify the viscosity and/or the texture of the medium, indeed even its rheological profile.
In highly viscous and solid media of the type of those intended to be employed in thermoplastics, thermosetting materials, elastomers and mastics, the microfibrils can modify the mechanical properties and can act in particular as reinforcing filler.
The advantageous mechanical properties of microfibrils are attributed to their specific structure; they have a highly hydrophilic nature due to the presence of hydroxyl functional groups at the surface of the microfibril.
However, the use of these microfibrils is not without disadvantage.
This is because the hydrophilic nature, which may be desirable in some applications, for example in aqueous and/or hydrophilic media, can constitute an obstacle to various applications desired in organic and/or hydrophobic media.
For example, in an organic and/or hydrophobic medium, the microfibrils do not disperse and phenomena of agglomeration and of flocculation occur, these phenomena being due to the incompatibility of the microfibrils with the organic medium in which they are found; as the microfibrils have a strongly hydrophilic nature, they will naturally have a tendency to flocculate and to agglomerate in an organic medium with a hydrophobic nature.
As a result of these phenomena, more particularly in an organic medium, the microfibrils will no longer be in a position to exercise their role of texturizing or viscosifying agent and/or of reinforcing filler.
An aim of the present invention is to provide cellulose microfibrils which, while having retained their initial morphological and crystalline aspects and thus all the advantageous mechanical properties which result therefrom, exhibit a markedly weakened hydrophilic nature.
Another aim of the invention is to provide microfibrils which can be dispersed in an organic medium.
These aims are achieved by the present invention, the subject matter of which is cellulose microfibrils with a modified surface, characterized in that the hydroxyl functional groups present at the surface of the microfibrils are etherified by at least one organic compound comprising at least one functional group which can react with the said hydroxyl functional groups and in that the degree of surface substitution (DSS) is at least 0.05.
The organic residues originating from the etherifying organic compounds attached at the surface of the microfibrils provide for better compatibility of the microfibril with the organic medium in which it is dispersed. The hydrophilic nature of the microfibrils is consequently markedly weakened and they can thus control the rheological properties of the medium.
At this stage, it is important to define the term “dispersibility”.
In the context of the present invention, the term “dispersibility” denotes the surface-modified microfibrils which, once introduced into an organic medium, are capable of dispersing with a gentle shearing and of forming a non-flocculating dispersion.
In other words, the microfibrils of the invention are rendered dispersible by a surface hydrophobicization of the hydroxyl functional groups: their initial morphology is retained and a crystalline arrangement is still observed.
Within the meaning of the invention, the term “organic medium” denotes a medium composed of an inert organic and/or hydrophobic liquid or of a mixture of inert organic and/or hydrophobic liquids in which the “unmodified” microfibrils do not disperse. When it is a mixture of liquids, they will preferably be miscible. Mention may be made, by way of indication, of:
alcohols, such as ethanol, isopropanol, butanol, hexanol or octanol;
aldehydes and ketones, such as butyraldehyde, acetone, methyl ethyl ketone or 4-methyl-2-pentanone;
cyclic or acyclic ethers, such as diethyl ether and its higher homologues, dioxane or tetrahydrofuran;
halogenated solvents, such as dichloro-, dibromo- or diiodomethane, chloroform, bromoform or carbon tetrachloride;
cyclic or acyclic alkanes, such as pentane, hexane, octane, dodecane, cyclopentane or cyclohexane;
optionally substituted aromatic solvents, such as benzene, toluene, chlorobenzene, bromobenzene;
alkyl acetates, such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate or pentyl acetate;
fatty acid esters, such as isopropyl myristate or the methyl esters of palmitic acid, stearic acid, arachidic acid, soybean oil fatty acid, rapeseed oil fatty acid, maize oil fatty acid, sunflower oil fatty acid or groundnut oil fatty acid.
The cellulose microfibrils can be of any origin, for example of plant, bacterial, animal, fungal or amoebic origin, preferably plant, bacterial or animal origin.
Mention may be made, as an example of animal sources of cellulose, of animals of the Tunicata.
The plant sources of cellulose can be wood, cotton, flax, ramie, certain algae, jute, sugarbeet pulp or citrus fruits (lemon, orange or grapefruit) or the like.
Whatever the origin of the microfibrils, they advantageously exhibit an L/D ratio of greater than 15, advantageously of greater than 50, more particularly of greater than 100 and preferably of greater than 500 and a mean diameter (D) of between 10 Å and 500 Å, advantageously between 15 Å and 200 Å, more particularly between 15 Å and 70 Å, preferably between 18 Å and 40 Å, L representing the length of the microfibrils and D their mean diameter.
The microfibrils can be obtained from the abovementioned cellulose sources by various processes already described in the literature. Reference may be made, among these processes, for example to the processes disclosed in European Patent Applications EP 0 726 356 and EP 0 102 829 or U.S. Pat. No. 4,481,076, the teachings of which on this subject are incorporated here.
According to a particularly advantageous embodiment of the present invention, the microfibrils are obtained by employing the process which will be described below.
More particularly, this process is carried out on pulp from plants with primary walls, such as, for example, beet pulp after the latter has been subjected to a stage of preliminary extraction of the sucrose, according to methods known in the art.
Thus, the process comprises the following stages:
(a) first acidic or basic extraction, on conclusion of which a first solid residue is recovered,
(b) optionally, second extraction, carried out under alkaline conditions, of the first solid residue, following which a second solid residue is recovered,
(c) washing of the first or second solid residue,
(d) optionally, bleaching of the washed residue,
(e) dilution of the first solid residue obtained on conclusion of stage (d), so as to obtain a solids content of between 2 and 10% by weight,
(f) homogenization of the dilute suspension.
In stage (a), the term “pulp” is understood to mean wet, dehydrated pulp preserved by ensiling or partially depectinized.
The extraction stage (a) can be carried out in an acidic medium or in a bas
Cantiani Robert
Chanzy Henri
Excoffier Gérard
Fleury Etienne
Gousse Cécile
Barts Samuel
Henry Michael C.
Rhodia Chimie
LandOfFree
Cellulose microfibrils with modified surface, preparation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cellulose microfibrils with modified surface, preparation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cellulose microfibrils with modified surface, preparation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3239383